|The Moon, imaged 2021 May 22 from Alexandria, Virginia,
with a 10.2-cm (4-inch) f/6.5 Explore Scientific AR102 refractor,
1.6X Antares 2-inch Barlow lens, and a ZWO ASI224MC color CCD imager.
The Moon waxes in the evening sky this week, brightening the southern horizon as she pays a visit to the giant planets Saturn and Jupiter. Full Moon occurs on the 20th at 10:57 Eastern Daylight Time. October’s Full Moon is widely known as the Hunter’s Moon to residents of the Northern Hemisphere. It shares similar horizon geometry to last month’s Harvest Moon. Just as the relatively short interval between successive moonrise events gave farmers a bit of extra illumination to bring in the harvest, this month a similar circumstance allows hunters to pursue game across the stubble of the harvested fields.
October 16th is International Observe the Moon Night, a NASA-sponsored event intended to bring worldwide attention to Earth’s only natural satellite. Weather permitting the gibbous Moon will be scrutinized by thousands of astronomers and casual skywatchers around the world to bring attention to our nearest neighbor in space. You won’t need fancy equipment to participate as Luna can be enjoyed with the unaided eye as well as optical aids like binoculars and small telescopes. If you have a telescope this presents a great opportunity to share your views with neighbors and friends. Here in the Washington DC area you can get a jump on the event by attending the Open House at the Analemma Society’s observatory at Turner Farm Park in Great Falls, Virginia. Beginning at 7:30 pm EDT on Friday the 15th, the observatory has four telescopes for public viewing. In addition, many local amateur astronomers come by to share the views through their instruments.
Why all the fuss about the Moon? I often say that she is “Looked over, then overlooked” by newcomers to astronomical observing. While her surface features have remained essentially frozen in time for hundreds of millions of years, subtle changes in lighting offer constant change in the way that these features appear. Luna’s surface turns out to be an almost bewildering array of great impact basins, lava flows, craters, mountains, and sinuous channels. All of these offer a wonderful alien landscape to enjoy from the comfort of your back yard, and it doesn’t matter if you live in the center of the city or way out in the country. Above all, the Moon represents the most distant frontier that humans have directly explored. While it is impossible to see the footprints, flags, and other hardware that were left behind by the 12 Apollo astronauts who walked on its surface, I can still feel their presence on that far-flung landscape that Edwin “Buzz” Aldrin called “magnificent desolation”.
The Moon’s brightening glow gradually hides the fainter stars of the autumn constellations, but there are a few bright stars that 5bright stars that still punctuate the night. High overhead at 8:00 pm local time you can see the stars that form the Summer Triangle asterism. Vega, Deneb, and Altair are easy to find from the city as they wheel toward the west as the night passes. By 10:00 pm the stars that form the “Great Square” of Pegasus climb toward the zenith, and by the early morning hours the stars of the Great Winter Circle, led by the familiar figure of Orion, ascend in the eastern sky.
The dazzling planet Venus is best seen in the southwestern sky as evening twilight falls. This week she passes just to the north of the ruddy star Antares, the heart of Scorpius, the Scorpion. She will pass her most southerly point in this year’s apparition late next week.
Saturn gets a visit from the Moon on the evenings of the 13th and 14th. The ringed planet crosses the meridian at around 8:00 pm, which is when he’ll be best placed for viewing in a telescope. Check out the nearby Moon while you’re in the area.
Giant Jupiter reaches the second stationary point of the current apparition on the 18th. He will gradually resume eastward motion over the next few weeks, putting more distance between himself and Saturn. It will be another 20 years before the two planets will encounter each other again. Look for the Moon near Jupiter and Saturn on the evening of the 14th. Luna follows Old Jove on the following evening, then leaves his vicinity until next month.
|NGC891, the "other" Andromeda galaxy,
imaged 2021 October 2 from Great Meadow, Old Tavern, Virginia
with a 10.2-cm (4-inch) f/6.5 Explore Scientific AR102 refractor
and a ZWO Optical ASI183 CMOS color imager
The Moon returns to the evening sky this week, waxing through her crescent phases as she dives to the southernmost reaches of the ecliptic. Look for Luna close to the dazzling planet Venus low in the southwestern sky on the evening of the 9th. If you have a clear view to the southwest look for the second-magnitude star Dschubba, one of three stars that mark the “head” of Scorpius, the Scorpion. It will be less than one degree above Venus on the same evening. First Quarter occurs on the 12th at 11:25 pm Eastern Daylight Time.
This is the time of year when we see the departure of one constellation in the west and the appearance of another one in the east. What’s interesting about this event is that both constellations are linked to each other in ancient sky lore.
As mentioned above, Scorpius is still visible in the southwest as evening twilight ends. Its brightest star, the red supergiant Antares, sets at around 9:00 pm local time, following bright Venus below the horizon by half an hour. By midnight a similar-colored star appears over the eastern horizon as the star Betelgeuse heralds the rise of Orion. Antares and Betelgeuse are stars with very similar characteristics. Both are highly-evolved massive stars that have swollen to gigantic proportions as nuclear fuel burns in expanding shells surrounding inert cores. Place either one in the Sun’s place in our solar system and our Earth would be swallowed up in the stars’ outer layers.
In mythology Orion was seen as a proud, powerful, and boastful hunter, son of the Gorgon Euryale and the Sea-god Poseidon. He claimed to have the ability to kill any animal on the planet, which raised the ire of Gaia, goddess of the Earth. To teach Orion a little humility Gaia sent Scorpius to kill Orion, but the Hunter was saved thanks to the efforts of Ophiuchus, whom the Romans associated with Asclepius, the first medical doctor. When it came time to place Orion in the heavens, Zeus place him in a spot opposite that of Scorpius so that the two would never meet each other again.
Between Scorpius and Orion another ancient mythological story plays out in the autumn evenings. The season’s brightest stars are climbing in the northeast, marking the constellations of Andromeda, Cassiopeia, Pegasus, and Perseus. Cassiopeia is identified by a “W”-shaped group of stars set in the faint band of the Milky Way. Pegasus is identified by a large square. Between Pegasus and Cassiopeia two diverging “chains” of stars mark Andromeda. Perseus lies between Cassiopeia and the horizon and to my eye forms a nice “wish-bone” asterism. These constellations were inspired by a story that dates back over 2500 years. In a nutshell, Cassiopeia, the vain Queen of Ethiopia, boasted that her beauty was greater than that of the half-mortal Sea Nymphs, who naturally objected to this brash claim. To exact a suitable penalty for her vanity, Poseidon forced Cassiopeia to chain her daughter Andromeda to a rock as a sacrifice to a sea monster. Fortunately, the hero Perseus arrives in the nick of time on his flying horse Pegasus, dispatches the sea monster, and frees the hapless Andromeda, whom he later married.
As mentioned earlier, Venus greets evening skywatchers during evening twilight. When she appears in the fading twilight you should be able to find Jupiter rising in the southeast. Old Jove is currently perched above a pair of stars, Deneb Algedi and Nashira, which mark the “tail” of Capricornus, the Sea-goat. Jupiter is nearing the second stationary point in this year’s apparition, so he’ll be close to the stars for the next couple of weeks.
Saturn reaches his second stationary point on the 11th and will gradually resume eastward motion across the stars of Capricornus through the rest of the year. You will find the ringed planet on the meridian at the end of evening twilight. This is the optimal time to view him through a telescope, since he will be at his highest elevation above the southern horizon. Any telescope will reveal the planet’s icy rings, so take a few moments to give him a look. You’ll be the “rock star” of your neighborhood!
|Messier 31, the Great Andromeda Galaxy,
imaged 2017 October 21 from Mollusk, Virginia
with a 10.2-cm (4-inch) f/6.5 Explore Scientific AR102 refractor
and a Canon EOS Rebel T2i DSLR
The Moon begins the week high among the rising winter constellations before she heads southward along the ecliptic toward the first stars of spring. She wanes from her Third Quarter phase to New Moon, which occurs on October 6th at 7:05 am Eastern Daylight Time. Due to her high declination she is very prominent in the clear autumn daytime skies for several hours after sunrise. If you’re up before the Sun on the 30th look for Luna near the bright stars Castor and Pollux, the Twin Stars of Gemini. On the morning of the 3rd she passes between the stars Regulus and Algieba, the two brightest stars in the rising constellation of Leo, the Lion.
With the Moon waning in the morning sky it is time for the October observing campaign for the Globe at Night citizen-science program. Sponsored by the National Science Foundation, the program aims to engage people to become aware of the night sky and the impediments to seeing it. So far this year over 21,000 observations have been submitted from observers around the world. The basic idea is simple: find a familiar constellation and see how many of its stars you can see. This month’s featured constellation is Pegasus, the mythical Flying Horse who figures prominently in the legend of Perseus and Andromeda. You will find Pegasus rising in the eastern sky at around 9:00 pm local time, but don’t expect to find a group of stars with a clear resemblance to a horse, flying or otherwise. The main feature of the constellation is a near-perfect square composed of second-magnitude stars leading to its popular name of the Great Square. The test of a dark sky lies in the number of fainter stars that you can identify within the Square’s bounds. To participate in the Globe at Night program, just go to the activity’s website and compare your view of Pegasus with the charts on the site, then report your results on the web app. From my bright suburban sky I can see the main stars in the square, but from rural sites I can spot about a dozen.
The Great Square of Pegasus follows the Summer Triangle asterism across the later evening skies. From a dark site you’ll notice that Pegasus is well away from the plane of the Milky Way. Behind the stars that form the constellation is an enormous gulf of empty space that is interspersed with scattered fuzzy blobs of light, the signatures of distant galaxies. Many of these are visible in modest telescopes, but one is actually visible to the unaided eye. To find it, locate the star Alpheratz, the brightest of the Square’s “corner” stars. Trailing this star is a diverging pair of star “chains” that delineate the constellation of Andromeda. “Star hop” to the second star in the brighter chain, and look a few degrees above it. Under dark skies you will see what appears to be a small detached piece of the Milky Way which, in fact, is another galaxy altogether. Known as the Great Andromeda Galaxy, that fuzzy blob is the combined light of some 200 billion stars located 2.5 million light-years away!
Venus is now moving along the southernmost reaches of the ecliptic. You can spot the dazzling planet low in the southwestern sky shortly after sunset, and as the sky darkens look for the stars of Scorpius to gradually appear. During the course of the week Venus closes in on the three stars that demark the Scorpion’s “head”. She will pass through those stars next week.
Saturn appears in the southern sky as darkness falls, leading the much brighter Jupiter across the southern sky. The ringed planet lies just under the third-magnitude star Dabih, which marks the “head” of the mythical Sea-goat Capricornus.
Jupiter finds himself on the opposite end of Capricornus, slowly drifting westward above the stars Deneb Algedi and Nashira, which mark the Sea-goat’s “tail”. The trio form a nice triangle for binocular owners, and careful scrutiny with these glasses will show Old Jove’s bright Galilean moons. However, Jupiter is also well worth viewing with a telescope. No other planet shows such a large and variable apparent disc. Smaller instruments will show the planet’s dark parallel equatorial cloud belts, while each increase in aperture will show more detail. Look for the planet’s famous Great Red Spot on the evenings of September 29th, October 1st, and October 4th.
|NGC 6992, the eastern arc of the Veil Nebula in Cygnus,
imaged 2021 September 11 at Great Meadow, Old Tavern, Virginia
with a 10.2-cm (4-inch) f/6.5 Explore Scientific AR102 refractor
and a ZWO ASI183MC CMOS color imager
The Moon climbs into the northern hemisphere of the sky this week, waning through her gibbous phases as she climbs into the rising stars of winter. Last Quarter occurs on the 28th at 9:57 pm Eastern Daylight Time. Look for the gibbous Moon perched between the bright star Aldebaran and the Pleiades star cluster as they rise in the late evening of the 25th.
The autumnal equinox arrives on the 22nd at 3:21 pm EDT. At this time the center of the Sun’s disc reaches an ecliptic longitude of 180 degrees and crosses the celestial equator into the sky’s southern hemisphere. Although the term “equinox” translates from Latin as “equal night”, the actual date when we experience exactly 12 hours between sunrise and sunset won’t occur until the 25th. This is due to the combined effects of the Sun having a disc that subtends about half a degree and atmospheric refraction. Sunrise occurs when the first discernable sliver of the Sun’s upper limb appears on the horizon, while sunset is when the last sliver of the disc disappears in the west. From September 26th until March 17th next year the nights will be longer than the days. The equinoxes are also the times when the length of daylight changes at its most rapid daily rate, about 2.5 minutes per day.
Early autumn evenings are a great time to catch up on exploring the splendors of the summer sky. The crisp evenings are generally free of the haze and humidity that’s inherent in the warmer months of July and August, and earlier sunsets mean that you don’t have to wait up for the sky to get dark. By 8:30 pm we reach the end of astronomical twilight, at which time the darkness of the sky is only limited by moonlight and artificial lights. At this time the three bright stars of the Summer Triangle may be found overhead, and the luminous band of the summer Milky Way bisects the sky from the southwest to the northeast. Under dark skies the Milky Way offers a treasure trove of star clusters and gaseous nebulae for owners of binoculars and small telescopes. Skirting the southern horizon, the “Teapot” asterism of Sagittarius offers a great place to start panning along the Milky Way. Looking just north of the teapot’s “spout” you will see a pair of bright knots of diffuse light. Binoculars will reveal these to be tight star clusters, while a telescope will show the stars enveloped in softly glowing clouds of gas. These so-called “nebulae” are stellar nurseries, and you can spot several more as you pan up to the bright star Altair. Within the bounds of the Summer Triangle you’ll find one of the denser star clouds of the Milky Way, along with a prominent dark “rift” that extends southward to the horizon. The prominent constellation of Cygnus, the Swan occupies most of the Triangle, and one can spend an entire evening just poking around the Swan’s environs. One of my favorite targets in Cygnus lies just off the eastern “wing” of the Swan. Wide-angle images show what appears to be a giant “bubble” nearby. This is the shattered remnants of a star that exploded some 20,000 years ago that is popularly known as the Veil Nebula. Ghostly wisps of light may be glimpsed in a low-power 4-inch telescope under dark skies, but long-exposure images reveal the delicate structure of expanding tendrils of the doomed star’s debris cloud.
Venus is still diving southward along the ecliptic, and this week the dazzling planet begins to close in on the “head” of the constellation of Scorpius, the Scorpion. On the evening of the 23rd binoculars will reveal the star Zubenelgenubi just two degrees north of the dazzling planet. In ancient times this star represented the southern “claw” of Scorpius, but today it marks the southern balance pan of the constellation of Libra, the scales, the only inanimate sign of the Zodiac.
Golden Saturn crosses the meridian at around 9:30 pm local time. This is the best time to check the ringed planet out with a telescope as he is as high in the sky as he will get for this apparition. The planet’s signature rings are still widely opened to our line of sight; they should show easily in just about any kind of telescope.
Giant Jupiter is the bright object that you’ve been seeing in the southeastern sky during the evening twilight hours. Old Jove spends the week close to the star Deneb Algeidi, the “tail” of the dim constellation of Capricornus, the Sea Goat. He follows Saturn to the meridian by just over an hour. His cream-white disc resolves in small telescopes, and instruments of three inches aperture will show his dark equatorial cloud belts. A six-inch instrument is sufficient to identify many more dark belts, and on occasion the Great Red Spot, an Earth-size storm that has persisted for some 300 years.
|Saturn & Jupiter, imaged at the U.S. Naval Observatory, 2021 September 8
with the 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor
and a ZWO ASI183MC CMOS imager
The Moon skims the southern horizon this week, waxing through her gibbous phases before reaching her full phase on the 20th at 7:55 pm Eastern Daylight Time. Luna will be a few degrees south of Saturn on the evening of the 16th. On the following night she lies just southwest of bright Jupiter.
As this Full Moon is the one that occurs closest to the autumnal equinox it is almost universally known as the Harvest Moon. I use the word “almost” because the phenomenon is only visible to residents of the Northern Hemisphere in September. Our friends “down under” see the same phenomenon, only for them it occurs six months later near the March equinox. It is a consequence of the Moon’s orbital geometry and one’s geographic location. The Harvest Moon is so named because before artificial lighting began to dominate the night farmers could use the light of the rising Full Moon to give them some extra time to bring in their fall harvests. At this time of year the plane of the Moon’s orbit intersects the horizon at a shallow angle for Northern Hemisphere observers, and the time between successive moonrises is about half of its more usual times during the rest of the year. Here in Washington the Moon rises only 29 minutes later on the nights before, during, and after Full Moon. The effect becomes more pronounced as you move to higher latitudes. Our friends at the Royal Observatory in Edinburgh, Scotland see successive moonrises that occur only 9 minutes later on the nights around Full Moon. Travel to Tromsø, Norway and you will find that Luna rises 20 minutes earlier on the nights around Full Moon! Similar circumstances occur around the time of October’s Full Moon, and in folklore this was seen as a boon to hunters, who could use the extra light from the Moon to pursue game across the stubble of the harvested fields.
The brightening Moon washes out the ghostly glow of the summertime Milky Way, but you can still see the path that the Galaxy traces across the sky. The season’s brighter stars delineate the plane of the Milky Way, forming the signature constellations of summer from the south to the north. In the early evening look for the red star Antares in the southwest. This is the brightest star in the constellation of Scorpius, the Scorpion, and you can trace out the other stars in Scorpius on either side of Antares. Just east of Scorpius is the “Teapot” asterism formed by the brightest stars in Sagittarius, the Archer. Halfway to the zenith in the south lies Altair, southernmost of the three stars that delineate asterism called the Summer Triangle, which lies directly overhead at 9:30 pm. The faintest of the three stars is Deneb, the brightest star in the constellation of Cygnus, the Swan, which is also known as the Northern Cross. Deneb is one of the most luminous stars in the sky, beaming across some 2500 light-years of space to grace our nights. Continuing northward, look for a group of five stars that trace out the letter “W”. This asterism forms part of the constellation of Cassiopeia, the legendary queen of Ethiopia memorialized in Greek mythology along with Perseus, whose stars are now rising in the northeast.
Venus continues her eastward trek along the ecliptic, steadily moving toward the stars of Scorpius. You can spot Venus in the southwest shortly after sunset and as twilight deepens her presence becomes more evident. She will continue to be a fixture in the early evening sky for the rest of the year.
The Moon visits Saturn and Jupiter this week, and the two giant planets figure prominently during the nighttime hours. Saturn shines with a subdued yellow tint, and crosses the meridian at around 10:00 pm. This is the best time to have a look at the ringed planet since it is the time when he’s highest above the horizon.
Jupiter’s follows Saturn across the sky, and you should have no trouble spotting him in the southeast during evening twilight. The giant planet’s glow rivals that of Venus, making him an easy target for telescopic observation. You will be rewarded for tracking him down as almost any telescope will show his four bright moons first documented by Galileo in 1610. Larger telescopes will reveal more detail in the planet’s turbulent atmosphere where winds blow with incredible ferocity. Watch Old Jove for an hour and you will see his rapid rotation and the constantly changing configuration of the four Galilean moons.
|Messier 27, the "Dumbbell Nebula", imaged 2021 September 4
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor
and a ZWO ASI183MC CMOS imager from Great Meadow, Old Tavern, Virginia
The Moon returns to the evening sky this week, emerging as a slender crescent in the southwestern sky on the evening of the 8th. On the evening of the 9th Luna will be a few degrees to the right of the brilliant glow of Venus. During the week the Moon skims the southern horizon and ends the week among the stars that form the “Teapot” asterism of Sagittarius. First Quarter occurs on the 13th at 4:39 pm Eastern Daylight Time.
The first full week of September finds the length of daylight dwindling by about 2.5 minutes per day. As the week opens Washingtonians experience 12 hours and 40 minutes between sunrise and sunset; in just over two weeks our days will become shorter than our nights. This, of course, is a boon to skywatchers, who now don’t have to wait until the late evening to enjoy fully dark skies. It’s a great time to enjoy the many wonders of the summer’s stars.
By 9:30 pm local time the season’s singular asterism, the Summer Triangle, lies directly overhead for most residents of northern temperate latitudes. The Triangle consists of the brightest stars in three separate constellations. The brightest of the three is Vega, which leads the diminutive constellation of Lyra, the Harp. Vega is located just 25 light-years from the solar system, and it is the fifth brightest star in the sky. Its brightness and proximity make it an ideal star for high-resolution spectroscopy, and it is arguably the most intensely studied star other than the Sun. It was the first star other than the Sun to be photographed back in 1850, and thanks to the precession of Earth’s rotational axis it will be the northern hemisphere pole star in about 12,000 years. Altair, the southernmost star in the Triangle, is even closer to us than Vega, a mere 16.7 light-years distant. Altair is noted for its exceptionally fast rotation rate, completing a single revolution in about 9 hours. In contrast, our Sun takes nearly 25 days to make one rotation. The third star in the Triangle is also its faintest, but not by much. Deneb is just over a magnitude fainter than Vega, but its actual luminosity belies its visual appearance. Deneb is much farther from us than its two bright companions, lying about 2500 light-years away. This means that it shines with the energy of around 200,000 Suns to appear as bright as it does in our sky.
Early in the week, when the Moon sets in the early evening, skywatchers in dark locations can see the soft glow of the Milky Way piercing the center of the Summer Triangle, then gently wafting down to the southern horizon to another signature summer asterism. This star pattern makes a credible outline of a teapot and consists of the brightest stars in the constellation of Sagittarius. Throughout the Milky Way a pair of binoculars or a small telescope will reveal bright and dark knots among the vast star clouds. Many of the brighter objects were first catalogued by the 18th Century French Astronomer Charles Messier, who made most of his discoveries from a hotel rooftop in Paris. Star charts of this area of the sky are littered with the “M” designation attached to his finds. Many of these objects are the spectacular targets of images from the Hubble Space Telescope. One of my favorites is an object located between Deneb and Altair in the very obscure constellation of Vulpecula, the Fox. Known as M27, it is a so-called “planetary nebula” produced when a low-mass star reaches the end stage of its evolution. Popularly called the “Dumbbell Nebula” due to its two-lobed visual appearance in small telescopes, its ghostly greenish glow reaches us from some 1400 light-years away.
Dazzling Venus graces the evening twilight in the southwestern sky, popping into view shortly after sunset. Often referred to as Earth’s “twin”, it is physically quite similar in mass and composition. However, the two planets are radically different. Venus has an atmosphere that consists almost entirely of carbon dioxide, which has caused a “runaway greenhouse” effect that heats the planet’s surface to a temperature that is hot enough to melt lead.
As evening twilight deepens, the solar system’s largest planets appear in the southeastern sky. Saturn shines with a gold-tinted hue well east of the “Teapot” asterism among the faint stars of Capricornus. Saturn’s distinctive rings make this one of the most enthralling sights in the sky. They are easily seen in small telescopes, and show more detail as you look with larger instruments.
Jupiter’s cheery glow follows Saturn across the sky. Binoculars will show the four bright moons discovered by Galileo in 1610, and a good three-inch telescope will show the planet’s dark equatorial cloud belts. If you have a six-inch or larger telescope you should be able to see many features in the planet’s clouds, including the famous Great Red Spot, an Earth-sized storm that has persisted for some 300 years. Look for the Spot on the evenings of the 7th, 9th, and 12th.
|Saturn and Jupiter, imaged 2021 August 25 from Alexandria, Virginia
imaged with a Celestron 23.5-cm (9.25-inch) f/10 Schmidt Cassegrain telescope and a ZWO ASI183MC CMOS imager from Alexandria, Virginia
The Moon is a waning crescent in the pre-dawn sky this week. If you’re up before the Sun, try to see Luna’s slender crescent just before sunrise on the 5th. New Moon occurs on the 6th at 8:52 pm Eastern Daylight Time.
The absence of the Moon in the evening sky means that it’s time for the September citizen-science observing campaign for the Globe at Night project. This week the featured constellation is Cygnus, the Swan, one of the principal constellations of the summer sky. Finding Cygnus should be fairly easy, even for suburban skywatchers. The Swan’s brightest star is Deneb, the northernmost and faintest of the stars that form the asterism known as the Summer Triangle. Deneb marks the Swan’s “tail”, while its “head” is marked by the third-magnitude star Albireo. A line of three second-magnitude stars trace out the Swan’s wings. Together these stars form another asterism sometimes called the Northern Cross. Another interpretation of this pattern, given to us by the Inuit people, is that of a man in a kayak paddling along the “Pebbly River”, the faint band of light that betrays the Milky Way. Cygnus is directly overhead for most residents of the “lower 48” at 10:30 pm local time, so it should be a simple matter to locate the constellation and compare your view with the star charts on the Globe at Night web app.
Cygnus is a wonderful constellation to explore with binoculars and small telescopes. One of my favorite sights is the aforementioned star Albireo. To the naked eye it looks like a single star located almost in the middle of the Summer Triangle. A small telescope at low power will reveal Albireo to be a stunning double star, whose components shine with Navy blue and gold tints. Located some 400 light-years away, the two stars may be a prime example of an “optical double”, created when two stars just happen to line up along our line-of-sight. Whether the stars are physically related or not, they provide an easy target for new telescope owners and can spark a life-long interest in observing other double stars. Between Deneb and Albireo lies the Cygnus star cloud, one of the most prominent features of the Milky Way. This is a great area to scan with binoculars from a dark sky site. The amorphous glow of the Milky Way begins to resolve into a myriad of faint stars interspersed with bright and dark knots. The bright knots are distant star clusters that resolve to varying degrees depending on the aperture of your telescope, while the dark patches are enormous clouds of cold gas and dust absorbing the light of the stars behind them. One bright knot just to the northeast of Deneb has a very distinctive shape that is best seen in binoculars. Known as the North America Nebula, this large, faint glowing cloud is the result of ionizing radiation causing hydrogen atoms to emit a subtle glow. Eventually this cloud of gas and dust will become a nursery for infant stars that will some day delight our distant descendants.
Venus is the bright object that you are undoubtedly seeing in the southwestern sky at dusk. This week the dazzling planet slides past the star Spica. The two objects will be closest together on the evenings of the 3rd and 4th. You will probably need binoculars to see the star, but you should have no trouble finding the bright planet.
Once Venus sets, turn your attention to the southeast, where two more bright planets command your view. The first of these is Saturn, whose soft yellow glow is only overshadowed by nearby Jupiter. This distant world, currently some 1.35 billion kilometers (842.5 million miles) away, is always a special treat for telescope owners. The planet’s rings can be seen with almost any instrument, but larger telescopes will reveal more detail in these icy appendages and subtle cloud belts in the planet’s atmosphere.
Jupiter shares the sky with Saturn and offers a larger disk for telescopic viewing. His most striking features are the alternating bright and dark cloud belts that define his upper atmosphere. Since Jupiter’s axial tilt is only about three degrees, these cloud belts are confined to specific latitudes on his surface. Small telescopes will easily show the dark equatorial belts that surround the planet’s bright equatorial zone, while larger instruments will show more alternating belts and zones. Subtle details in these belts and zones change daily, and since the planet rotates in less than 10 hours a new area of interest is constantly rotating into view.
|Messier 8, the Lagoon Nebula in Sagittarius
imaged with an Antares Sentinel 80-mm (3-inch) f/6 refractor
and a Canon EOS Rebel T2i DSLR from Morattico, Virginia
The Moon wanes in the morning sky this week among the faint stars of the autumnal constellations. Luna climbs northward along the ecliptic, ending the week among the rising stars of the Great Winter Circle. Last Quarter occurs on the 30th at 3:13 am Eastern Daylight Time. Look for the Moon between the Pleiades and Hyades star clusters in Taurus before dawn on the morning of the 30th.
It’s a bit hard to believe that the autumnal equinox is less than a month away, but if you’ve been paying attention to the times of sunrise and sunset you have noticed that the days are rapidly becoming shorter. During the course of the week sunrise occurs five minutes later and sunset occurs 10 minutes earlier, and the total length of daylight is just over 13 hours. We will lose another hour of daylight over the course of the next several weeks.
As the Moon drifts farther into the morning sky and evening twilight ends at an earlier time we can turn our attention to the striking panoply of the summer sky. If you are planning to have a final summer vacation trip to the beach or the mountains, this is the time to spend some quality time under the stars. From sites well away from city lights you can enjoy the sight of the summer Milky Way, which carves an amorphous arc across the sky from the northeast to the south. The southern reaches of the Milky Way take up much of the southern view of the sky and form a softly glowing background to many of the season’s most prominent constellations. When we look in this direction we are looking toward the center of our home galaxy, but we can’t actually see its bulging nucleus. Notice the dark incursions into the pale glow of these distant star clouds. These are areas of cold gas and dust that absorb the light of the galaxy’s distant heart. The star clouds that we are able to see are some 8,000 light-years distant, but the galactic center is another 20,000 light-years beyond the cloaking dark clouds. This is a wonderful area to sweep with a pair of binoculars or a low-power telescope; the softly glowing clouds resolve into a myriad of stars, and sprinkled among them are glowing gaseous nebulae and glittering star clusters.
One of my favorite asterisms crosses the meridian just above the southern horizon at 10:00 pm local time. Popularly known as The Teapot, it consists of the brightest stars of the constellation Sagittarius, the Archer. The teapot is fairly easy to trace out, especially if you can see the Milky Way. One of the galaxy’s brightest star clouds seems to emanate from the Teapot’s “spout” like a cosmic cloud of steam. Just below the “spout” is one of the sky’s best binocular treats. Messier 7, sometimes called Ptolemy’s Cluster, easily resolves into dozens of twinkling gems. Just above the “spout” you will find several bright knots that are also good binocular targets. The brightest of these is Messier 8, also known as the Lagoon Nebula. Here you will find a star cluster embedded in a cloud of glowing gas. This is an area of continuing star formation similar to the Great Nebula in Orion. It is a wonderful sight in a low-power telescope field. Continue sweeping northward above the lagoon Nebula to see dozens of other clusters and glowing nebulae.
Bright Venus continues to press eastward along the ecliptic, wending her way southward as well. This week she closes in on the bright star Spica, which she will pass in early September. She currently sets at the end of evening astronomical twilight, but as fall progresses she will begin to command a higher place in the sky.
Golden Saturn trails the Teapot across the southern horizon. The ringed planet lies among the dim stars of the constellation Capricornus, the Sea-Goat. The planet’s distinctive rings are easily seen in a small telescope, and larger instruments will show detail in the rings and the planet’s delicately striped orb set among a sprinkling of faint moons.
Jupiter appears shortly after sunset in the southeastern sky, and is outshone only by Venus in the southwest. The giant planet now dominates the overnight hours and presents another great target for the casual skywatchers. His four bright Galilean moons are visible inn binoculars, while a four-inch telescope will reveal the planet’s equatorial cloud belts. These dark belts are zonal intersections between jet streams in the planet’s vast atmosphere that move past each other at speeds approaching 1000 kilometers per hour. I’m very glad that I don’t live there!
|Saturn and its moons, imaged 2015 July 12 at the U.S. Naval Observatory
with the 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor.
We’ll be taking a brief break from the Washington heat next week, so this edition won’t be updated on the 17th.
The Moon returns to the evening sky, starting the week in the company of bright Venus before gliding southward along the ecliptic. First Quarter occurs on the 15th at 11:20 am Eastern Daylight Time. Full Moon will occur on the 22nd at 8:02 am EDT. August’s Full Moon is popularly called the Corn Moon, Barley Moon, and Fruit Moon, but the name that most folks recognize is the Sturgeon Moon. This name comes from Native American lore as the indigenous people living along the shores of the Great Lakes noticed that these large fish were most easily caught when this particular Full Moon was in the sky. Luna passes south of Saturn on the evening of the 20th; on the following night she rises with Jupiter.
This week’s highlight is the peak of the annual Perseid Meteor Shower, which occurs during the overnight hours of the 11th and 12th. This display is the most consistent and productive of the annual meteor showers, and this year it occurs well after the Moon has set. These meteors originate from debris sputtered off Periodic Comet 109P Swift-Tuttle, which circles the Sun on an eccentric path every 133 years. The comet was co-discovered by Lewis Swift and Horace P. Tuttle in July, 1862 and was linked to the Perseid meteor stream by the Italian astronomer Giovanni Schiaparelli in 1866. Records of the Perseids date back over 1000 years, when early Christians identified them with the “Tears of St. Lawrence”, who was martyred on August 10, 258 CE. Under clear skies at a dark location a single observer can expect to see up to 75 to 100 fast-moving meteors per hour. If you follow the meteor trails backwards you will find that they seem to originate from a point in the sky, known as the radiant, in the constellation of Perseus. The radiant rises in the northeast in the late evening and climbs higher in the east during the morning hours. The best way to observe them is comfortably seated in a beach chair with a clear view of the sky. No telescope required! Although the shower is expected to peak on the night of August 11-12, you can expect to see Perseids for several nights afterward.
If you are out in the wee hours watching for Perseids, take a few minutes to look for one of the most unusual stars in the sky. Sprawling over the southeast horizon, the constellation of Cetus, the Whale sports few bright stars. Its brightest star, Diphda, marks the whale’s head, and its second-brightest star, Menkar, forms part of its tail. About one-third of the way from Menkar to Diphda you should see a star of comparable brightness that is normally not there. This star, Mira, is the prototype of a type of star called a long-period variable. Roughly every 330 days the star reaches a peak in its brightness, then fades to invisibility some 1700 times fainter than its peak. The star is near its peak brightness, which should occur on the 18th, and recent reports indicate that it is now the second-brightest star in the constellation.
The evening sky sports a nice selection of bright stars for the casual skywatcher. As evening twilight ends the bright star Arcturus beams down from the western sky, and Spica twinkles furiously in the southwest. The northwestern sky holds the asterism known as the Big Dipper, which slowly moves to skim the northern horizon in the early morning hours. The late night hosts the three bright stars of the Summer Triangle, Vega, Altair, and Deneb, while the ruddy star Antares leads the stars of Scorpius across the southern skyline.
Venus is the bright object that you are seeing in the western sky as evening twilight gathers. The planet’s dazzling glow is due to its cloud-laced atmosphere, which reflects nearly 70 percent of the sunlight that strikes it. As beautiful as these clouds appear, though, you wouldn’t want to fly through them; they are composed of sulfuric acid!
Saturn is now high enough by 9:00 pm local time to enjoy a long look through the telescope. The view of the planet’s cream-colored disc floating inside its system of rings is one of the most enthralling sights in all of Nature, and I never get tired of looking at it. There is something almost magical about seeing it for the first time “live” in the eyepiece.
Jupiter reaches opposition on the evening of the 19th. At this time the giant planet rises at sunset and sets at sunrise. He is ready to view in the telescope by 10:00 pm, and offers his own interesting sights to see. A casual glance will reveal the bright moons first described by Galileo in 1610. Depending on the time of your observation, you can see two, three, or all four of these near planet-sized bodies in the gravitational grip of their huge master. Sometimes they pass into the planet’s shadow, while at others the moons drag their tiny shadows across Old Jove’s vast face. Close scrutiny will show the planet’s striped atmosphere, which is under a state of continuous change.
|The Milky Way, imaged 2017 August 21 from Smith's Ferry, Idaho
with a Canon EOS Rebel SL2 DSLR.
The Moon begins the week as a slender waning crescent in the pre-dawn sky. New Moon occurs on the 8th at 9:50 am Eastern Daylight Time. Early risers can watch Luna pass through the rising stars of the Great Winter Circle. She returns to the evening sky on the evening of the 10th, when you will find her near the dazzling planet Venus.
The August campaign for the Globe at Night citizen-science program is underway and runs through the evening of the 8th. So far this year the program has received over 20,000 reports from observers around the world who are recording the faintest stars that they can see in their skies. The procedure is simple; find the target constellation, compare your view with reference charts on the Globe at Night website, and report your results. If you are away from your computer, the program has apps for smart phones that can assist you in finding your limiting stellar magnitude and reporting your results. The aim of the program is to measure the spread of “light pollution” that is affecting more and more of the night sky. Bright nighttime lighting not only robs us of the view of our place in space, it has a number of dire effects on wildlife and humans, upsetting circadian rhythms and navigation for migrating species. It is one environmental issue that has a relatively easy and inexpensive fix, and the energy savings from sensible lighting will also lower carbon emissions that contribute to climate change.
Most of us associate early August with the heat and humidity of the so-called “Dog Days” of popular lore. The origin of this expression is, of course, astronomical, and it dates back to very early times. The “Dies Canicularum” of the ancient Romans corresponded with the first appearance of the bright star Sirius rising just before the Sun. Sirius is the brightest star in the sky after the Sun, and it is the hallmark of the constellation Canis Major, the Greater Dog in Roman skylore. The star’s name derives from the ancient Greek word for “scorcher”, and it was thought that the light of the star augmented that of the Sun and led to the hot, sultry days of the season. This “heliacal rising” of Sirius has roots which pre-date the Romans by two millennia. Ancient Egyptians noticed and recorded the phenomenon around 3000 BCE and saw that it corresponded to the annual life-giving flood of the Nile River. This became the most important date in the Egyptian agricultural calendar and formed the basis for their civilization’s success.
August is the month to get out and enjoy the splendors of the summer sky. Many of us take vacations at this time of year, and any escape from the light-domes of urban areas should include time to look up and see the stars. Whether you’re staying at the beach or camping in the mountains, plan to spend some time taking in a view of our wonderful universe. There are many apps for your phones and tablets that can help you navigate the night sky, but even without these you can still find wonders. By 10:00 pm the sky is fully dark, and the ghostly glow of the Milky Way rises from the southern horizon. The Milky Way’s path is sprinkled with bright stars that form familiar patterns like the Summer Triangle, Scorpius, and the “Teapot”. Start your interstellar adventure by identifying these patterns, then see how many more you can find.
The bright glow of Venus climbs a little bit higher above the western horizon each night. You should have no trouble spotting her piercing white light shortly after sunset. By the end of the week she is joined by the Moon, whose slender crescent is nearby on the evenings of the 10th and 11th.
As Venus settles in the west, Saturn climbs higher into the southeastern sky. Saturn’s glow is much more subdued than that of Venus, but he is still easy to spot among the dim stars of the constellation of Capricornus. The planet’s famous rings can be seen in small telescopes, but they really show off in apertures of six inches or more. On nights with steady air and good transparency look for several of the ringed planets many moons, looking like tiny fireflies around the planet’s light.
Jupiter follows Saturn’s path into the southeastern sky. You won’t have any trouble finding the giant planet by 10:00 pm, but you should wait another hour before training the telescope on him. His cream-colored disc is crossed by two prominent dark stripes in small telescopes, which will also easily show his four Galilean moons. Larger instruments reveal more detail in his turbulent atmosphere especially when the air is steady.
|Saturn, imaged 2018 August 24 at the U.S. Naval Observatory
with the 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor telescope
The Moon spends much of the week passing through the dim constellations of the autumn sky as she wends her way northward along the ecliptic. Last Quarter occurs on the 31st at 9:16 am Eastern Daylight Time. Luna keeps a lonely vigil until the first few days of August, when you can find her near the Pleiades star cluster before dawn on the 2nd. On the following morning she lies northeast of the bright star Aldebaran.
August 1st is, for many of us, the unofficial date when we start our annual summer vacations. It is also one of the ancient dates known as “cross-quarter” days that were once widely observed in medieval Europe. These dates fell roughly mid-way between the dates of the astronomical seasons and provided important anchors in the lives of serfs and their masters. The traditions associated with three of these cross-quarter days are still observed today as Halloween, Groundhog Day, and May Day, but hundreds of years ago these, along with the solstices and equinoxes, were the dates when landowners collected their rents from their tenants. Cross-quarter days became ingrained in many pagan European cultures, and were especially important to the Celts. The August date was celebrated as Lughnasadh in honor of the pagan god Lugh, who brought the bounty of the annual harvest to humankind. As Christianity swept through Celtic lands the date became known as Lammas, or “Loaf-mass”, the day that freshly baked loaves of bread made from the first grain harvest would be brought to church to be blessed. Lammas is still observed by the Church of England and is one of the key celebrations in the “Book of Common Prayer”.
It is usually around this time of year when most of us begin to notice the earlier daily setting of the Sun. Sunset occurs about a minute later each successive evening as August begins, but by the end of the month the difference approaches two minutes. Earlier sunsets mean that we have a bit more time each evening to enjoy the splendors of the summer sky, which for me is dominated by the bright star clouds of the Milky Way. By 10:30 pm the densest of these clouds may be seen crossing the meridian in the southern part of the sky. Gazing in this direction brings our line-of-sight to the center of our home galaxy, looking like a cloud of steam rising from the “spout” of the “Teapot” asterism in Sagittarius. This “steam” consists of the unresolved light of millions of stars that blend into an amorphous haze and begins to resolve in a pair of binoculars. My favorite views, though, are through my four-inch telescope with a low-power eyepiece. Not only is the view chock full of uncountable stars, it is punctuated by compact concentrations of glowing gas, star clusters, and curious voids where no stars appear at all. These “dark nebulae” are actually cool clouds of gas and molecular compounds that obscure the light of the stars behind them. This dark material is easily viewed with the naked eye as you look higher along the Milky Way’s luminous band, particularly between the stars that form the Summer Triangle asterism. In the Southern Hemisphere, where the central parts of the Milky Way lie overhead, many cultures created “constellations” out of these dark rifts and whirls snaking their way through the star clouds.
Venus continues to slowly edge her way up from the western horizon during the evening twilight hours. You should have no trouble spotting her by 9:00 pm local time. She is drifting eastward among the stars of the constellation of Leo, the Lion, and is gradually setting her sights on the bright star Spica, which may be seen low in the southwestern sky.
Much harder to spot is Mars, which is now losing ground on the ever-advancing Sun. The red planet will require binoculars and a very clear sky to successfully track down. On the evening of the 29th he will be just over half a degree northeast of the star Regulus, a few degrees above the western horizon at 9:00 pm.
Saturn reaches opposition at 2:00 am EDT on the morning of the 2nd. This is the date when the ringed planet rises at sunset and sets at the following sunrise. He should be well-placed for viewing in the telescope by 11:00 pm.
Giant Jupiter rises around an hour after Saturn and should be a tempting telescopic target by local midnight. These two planets offer a great view in small telescopes. Jupiter lords over his four bright Galilean moons, and Saturn exhibits his spectacular system of rings. I’m looking forward to spending many warm late summer evenings with these worlds.
|Mount Wilbur by Moonlight, 2021 June 28, imaged in Glacier National Park, Montana
with a Canon EOS Rebel SL2 DSLR, 18mm f/5.6, 30 seconds @ ISO6400
The Moon skims the southern horizon this week, waxing through her full phase before gradually climbing through the rising autumnal constellations. Full Moon occurs on the 23rd at 10:37 pm Eastern Daylight Time. July’s Full Moon is popularly called the Thunder Moon in some traditions; other names include the Buck Moon and Hay Moon. Look for the Moon near rising Saturn on the evenings of the 3rd and 24th. She rises with bright Jupiter during the late evening of the 25th.
July 20th is a special day for those of us who have grown up in the so-called “Space Age”. On that date in 1969 Neil Armstrong and Edwin “Buzz” Aldrin touched down on the lonely expanse of the Moon’s Sea of Tranquility, fulfilling the age-old dream of walking on the surface of another world. Just five years later a three-legged emissary from Earth successfully landed on a far more distant and rocky shore on the Chryse Planitia region of Mars. As with the Apollo 11 landing, I found myself glued to the TV set in the wee hours of the morning as the Viking 1 lander approached the surface of the red planet. Unlike the Apollo lunar module, however, Viking had no pilots, and it took more than eleven minutes for the success of the landing to reach controllers on Earth. As the first image from the lander slowly scrolled across the TV screen, it was almost impossible to imagine that I was looking at the surface of another world. Our voyages to the bounds of the solar system since those two July days have given all of us an opportunity to experience the thrill of discovery as we peel back the mysteries of our planetary neighbors.
Scattered light from the bright Moon and smoke from wildfires in the American west and Canada will diminish the splendor of the midsummer sky this week. That said, the subdued sky still reveals a few bright targets that you can use to find more subtle sights when conditions improve. Early in the evening we can see two holdovers from the spring in the form of the bright stars Arcturus and Spica. Arcturus, the brightest star in the northern hemisphere sky, may be found high in the west once the sky becomes dark. Spica glows from the southwestern part of the sky. By 10:00 pm you may be able to pick out the seven stars of the Big Dipper asterism. These stars are visible to us year-round, but if you follow their progress across the sky overnight you will see the Dipper skim the northern horizon in the early morning hours. In the east the three stars of the Summer Triangle, Vega, Altair, and Deneb, climb toward the meridian as evening turns into morning. These stars outwardly appear similar, but we now know that the faintest of the trio, Deneb, is a star of almost unimaginable luminance. Vega and Altair are relatively nearby at 25 and 16.7 light-years, respectively, but Deneb is 100 times more distant than Altair. To appear as bright as it does in our sky Deneb must shine with the equivalent light of nearly 200,000 Suns! If we could somehow drag Deneb to Altair’s distance it would shine with nearly the same apparent brightness as a full Moon. Night would be a very different experience if that were the case.
Go out about half an hour after sunset and look for the bright glow of Venus about 10 degrees above the western horizon. If you have a pair of binoculars, look near the planet’s dazzling glow for the fainter light of the star Regulus. Over the first few nights of the week Venus is close to the star, with a minimum one degree separation at dusk on the 21st.
Mars follows Venus, reaching the proximity of Regulus by the week’s end. Mars is also much dimmer than Venus, and is actually dimmer than the star. You will most likely need binoculars to pull the red planet out of the horizon haze.
Saturn now rises before 9:00 pm, and by midnight he should be well-placed for viewing through the telescope. The ringed planet is just under two weeks from opposition, when he will shine in the sky all night long.
The much brighter giant planet Jupiter rises one hour after his more distant companion, and by midnight he, too should be a good sight in the telescope. Try to find a spot to observe these two worlds that has a flat horizon with no buildings. Their southerly declination makes viewing them more susceptible to atmospheric currents on these muggy summer nights.
|Crescent Moon with Venus & Mars, imaged 2021 July 12 from Alexandria, Virginia
with a Canon EOS Rebel SL2 DSLR. HDR composite of four exposures
The Moon waxes as she dives southward along the ecliptic this week. First Quarter occurs on the 17th at 6:11 am Eastern Daylight Time. On the evening of the 16th you’ll find Luna to the northwest of the bright star Spica. By the end of the week the Moon will pass north of the star Antares in the constellation of Scorpius.
Each year in mid-July I take the time to reflect on an event that was a pivotal one in my experience. Fifty-two years ago I, along with millions of other people around the globe, spent the better part of a week glued to our television sets as the Apollo 11 flight to the Moon played out. From the liftoff of the massive Saturn-V rocket on the morning of July 16th to the splashdown of the tiny Command Module “Columbia” eight days later, I followed the flight almost minute-by-minute. One of the memories that stands out is watching Neil Armstrong take the first steps by a human on the surface of another world while simultaneously looking at the Moon through my 3.5-inch telescope. Outwardly the Moon looked the same as it had countless times before, but somehow on that night it was very different. There were three fellow humans up there, two on the surface and one in orbit, and although I couldn’t see them, I sensed their presence in the eyepiece. Since that time I have never looked at the Moon without knowing that we went there, if only for few fleeting moments. Each year I set the telescope up in my yard when the Moon is close to the same phase that it had on July 20th, 1969. This year that evening will be the 15th. The view never gets old.
The hazy nights of midsummer often mask the splendors of the season’s skies, but with a little patience you can find plenty of interesting sights to see despite the less-than-ideal conditions. Summer is the season for globular star clusters, which are spherical swarms of tens of thousands of stars that orbit the galactic center. About 150 of these clusters are known in the Milky Way’s environs, and the vast majority of them are visible during the summer and autumn months. Small telescopes show these clusters as spherical puffs of amorphous light, while a four-inch instrument will begin to resolve the brighter ones. My 8-inch reflector betrays the stellar nature of all but the most distant ones. Two of these clusters lie very close to bright stars in the summer sky and are quite easy to locate. The first is Messier 4, which lies just over a degree west of the star Antares inn Scorpius. This cluster should easily resolve in 4- to 6-inch telescopes, especially if you move Antares out of the field of view. Under dark skies the smaller, more distant cluster NGC 6144 may be glimpsed just a degree northeast of M4. One of my favorite globulars, Messier 22, may be found in the adjacent constellation of Sagittarius. This constellation contains an asterism formed by its brightest stars known as “The Teapot”, and the cluster lies just over two degrees northeast of the star Kaus Borealis, the star that marks the Teapot’s “top”. This is a bright, well-resolved cluster that is ideal for the small telescope. Once again, there are other more distant clusters near the reference star. Messier 28 lies just one degree west of Kaus Borealis, while the far-flung cluster NGC 6638 is located just half a degree to the east.
Early evening is now dominated by the bright glimmer of the planet Venus. The dazzling planet begins the week fresh from a close conjunction with the more distant Mars, but she quickly leaves her companion world in her wake as she presses eastward through the setting springtime stars. If you have binoculars look for the bright star Regulus to the east of Venus. By the end of the week the bright planet will close ranks with the star, which she will pass early next week.
Mars now lags behind his brighter rival and will continue to lose ground to Venus as he gradually sinks into the twilight haze. You will probably need binoculars to glimpse him as he also pursues the star Regulus.
The gas giants Saturn and Jupiter can now be seen in the late evening sky, glowing brightly in the southeast. Saturn rises at around 9:30 pm local time while Jupiter follows about an hour later. After the Moon, these two distant worlds are the night’s best targets for small telescopes. Jupiter sports his four bright Galilean moons and delicate streaks in his atmosphere, while Saturn displays his incomparable rings. They are well worth staying up late for.
|Scorpius (Antares at center right) and the summer Milky Way, imaged 2020 July 26 from Mollusk, Virginia
with a Canon EOS Rebel SL2 DSLR and and an Omegon LX2 mechanical star tracker. Note Jupiter & Saturn to the left.
The Moon returns to the evening sky by the latter part of the week, with New Moon occurring on the 9th at 9:17 pm Eastern Daylight Time. Luna joins the twilight planets Venus and Mars on the evenings of the 11th and 12th. With the two planets undergoing a close conjunction, the Moon’s addition should make for a fine photo opportunity.
The time of sunset is now gradually becoming earlier for those of us who enjoy stargazing at a decent hour. However, we’ll have to wait a few more weeks before most of us will notice a significant change. Sunset won’t occur before 8:30 pm until the evening of July 20th here in Washington.
Once the sky does become fully dark, the absence of the Moon’s bright glow allows us to enjoy the splendors of the summer sky. The last of spring’s constellations are setting, while the bright stars of the Summer Triangle stand out prominently in the east. By 10:30 pm one of summer’s most prominent constellations reaches prominence on the southern horizon. Scorpius never rises very high in the sky for those of us in temperate northern latitudes, but it’s worth the time to find a good viewing spot with an open southern sky to look for it. Its brightest star, Antares, crosses the meridian at around 10:30 pm. It is notable for its red tint, which is similar to that of Betelgeuse in the winter sky. To the west of Antares you’ll see a near-vertical line of three blue-hued stars that outline the scorpion’s head, but it’s the arc of stars that sweep down to the horizon, then curve upward to the east of Antares that give the scorpion its distinctive shape. A close pair of stars indicate the beast’s fearsome stinger.
Scorpius is one of the few constellations that resembles its namesake, and as such its origins go way back in time. One of the earliest depictions of the constellation date to the pre-dynastic period of ancient Egypt, where a stone mace-head depicts an early king performing a ritual opening of an irrigation canal. The scorpion is depicted as his personal glyph, and it is very likely that he associated himself with the scorpion in the sky. The mace-head has been dated to c. 3200 BCE.
Of course, different cultures don’t necessarily see the same patterns in these stars. Polynesians see the scorpion’s curving tail as an asterism representing the giant fish hook used by their creator god Maui to dredge islands up from the bottom of the Pacific Ocean.
From a dark sky, look above the two stars in Scorpius’ “stinger” to see the dense star clouds of the summer Milky Way. When we gaze in this direction we are looking toward the central bulge of our home galaxy. This is a particularly spectacular region to scan with binoculars or a low-power telescope. The formless glow of the Milky Way reveals itself to be the combined light of millions of distant stars, and sprinkled among these are clusters of closer stars and the glow of star-forming clouds of gas and dust.
The evening twilight hours offer the most interesting phenomena of the week. You should be able to spot the bright glow of Venus above the western horizon shortly after sunset, and an hour later ruddy Mars should appear nearby. Depending on the clarity of the sky you may need to use binoculars to spot the red planet, but by the week’s end Venus will cozy up to within half a degree of the dimmer Mars. On the evening of the 12th Mars will be just to the left of Venus, and on the following night Mars will be to the right of the dazzling planet. The crescent Moon is near the pair on the 12th and 13th.
By midnight the solar system’s two giant planets Saturn and Jupiter can be seen in the southeastern sky. Saturn rises first, and should be a good telescopic target. Jupiter lies farther to the east, and you’ll probably need to wait another hour to train the telescope on his cloud-streaked surface. Both planets will become better placed for evening viewing over the next several weeks.
|Amber Moon rising, imaged 2020 December 29 at Ocean City, Maryland
with a Canon EOS Rebel SL2 DSLR and 300mm lens
The Moon brightens the evening sky this week, wending her way through the southern reaches of the ecliptic as she waxes to Full Moon, which occurs on the 24th at 2:40 pm Eastern Daylight Time. June’s Full Moon is popularly known as the Strawberry Moon since this is the peak season for harvesting these sweet treats. Other names are the Green Corn Moon, Hatching Moon, Hot Moon, and Honey Moon. The latter name is not only associated with the month as the most popular one for weddings, it is also a good descriptor of the light amber hue that the Moon takes on as she courses through these southern declinations. Her light not only has more of Earth’s atmosphere to penetrate, that summer air is often hazy, further tinting the Moon’s glow. Luna begins the week just north of the red-tinted star Antares, the heart of Scorpius, the Scorpion. You will find her near the rising planets Saturn and Jupiter on the 26th, 27th, and 28th. Last Quarter occurs on July 1st at 5:11 pm EDT.
The year’s latest sunset for temperate northern latitudes occurs on June 28th, closing out the phenomena associated with the summer solstice. Here in Washington Old Sol slips below the western horizon at 8:38 pm EDT that evening, then begins to slowly set earlier on successive nights. Despite these latest evening sunsets, the total length of daylight is gradually decreasing, a trend that will continue for the next six months. For those of us who relish the dark night sky, this is also the time when we have to wait the longest to ply our trade. Evening astronomical twilight doesn’t end until 10:37 pm, which is almost past my bedtime!
Another annual phenomenon occurs on July 5th at 6:27 pm EDT. At that time the Earth will reach aphelion, its greatest distance from the Sun. At that moment we will be 152,100,514 kilometers (94,510,878 miles) from the “Day Star”. The interval between successive perihelions defines the “anomalistic year”, which is about 25 minutes longer than the “tropical year”, which the interval between successive vernal equinoxes. This causes the dates of these “apsides” to gradually slip later through the years. In the year 1800 Aphelion occurred on June 30th.
Late June evenings offer a transition from the springtime constellations to the rising stars of summer. By the end of evening twilight the bright springtime star Arcturus has passed the meridian and starts to heel to the west. The Big Dipper is prominent in the northwest, but it, too is diving westward as the night passes. Looking eastward, the rising stars of the Summer Triangle asterism are making their way toward the meridian. The brightest of these stars, and the highest of the trio, is Vega, lead star of the diminutive constellation of Lyra, the Harp, and fifth-brightest star in the sky. It is one of our nearest bright stellar neighbors, shining at a distance of 25 light-years. Another near neighbor is Altair, the southernmost star in the Triangle. It is the brightest star in Aquila, the Eagle, and it lies just under 17 light-years away. The final star in the asterism is Deneb, brightest star in Cygnus, the Swan. Although it appears on par with its two companions, it is not a nearby jaunt away. It is located at a staggering 2500 light-years distance! To appear as bright as it does in our sky it must shine with nearly 200,000 times the luminosity of our Sun.
Venus should now be easy to find in the west during fading evening twilight. She begins the last week of June near the stars Castor and Pollux, and draws a bead on the slower-moving planet Mars.
Mars opens the week nestled among the stars of the galactic star cluster known as the Praesepe or “The Beehive”. This cluster should be easy to spot in binoculars and is probably the most distinguishing feature of the star-poor constellation of Cancer, the Crab. Mars lies smack in the middle of the cluster on the evening of the 23rd. Once the red planet leaves Cancer he’s looking over his shoulder at the rapidly-approaching Venus.
Saturn and Jupiter are now rising before midnight and continue to make inroads into the evening sky. They are still best seen by night-owls and early risers, but by the end of July they will be well-placed for late evening observation. The pair entertain the Moon on the last few nights of June.
|The Moon, imaged 2021 May 19, 02:00 UT from Alexandria, Virginia
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor, 1.6X Antares Barlow lens,
and a Canon EOS Rebel T2i DSLR.
The Moon waxes through her crescent phases this week as she wends her way through the late spring and early summer constellations. First Quarter occurs on the 17th at 11:54 pm Eastern Daylight Time. Luna starts the week among the stars that form the “head” of Leo, the Lion, then works her way southeastward through Cancer, Virgo, and Libra before finishing the week among the stars of Scorpius. Look for the Moon to the north of the bright star Spica on the evening of the 19th. On the 22nd she passes to the north of the ruddy star Antares.
The summer solstice occurs on the 20th at 11:32 pm EDT. This is the moment when the center of the Sun’s disc reaches an ecliptic longitude of 90 degrees. It is also when Old Sol reaches his highest northern declination, providing us with our longest days and shortest nights. The opposite case is true for our friends in the southern hemisphere, who are experiencing the start of their season of astronomical winter. The observation of the solstice has been a focal point in the sky calendars of many ancient cultures, and we see remnants of these calendars scattered throughout the world. Perhaps the most famous of these is Stonehenge on the Salisbury Plain in southwestern England. This famous megalithic structure has seen the annual rise of the Sun on the day of the solstice for millennia. The iconic stone circle that most of us are familiar with sits on a site that had been in use for well over 1000 years for marking this annual event. The earliest phase of the monument was constructed around the year 3100 BCE, about the time that the Old Kingdom of ancient Egypt arose. The Neolithic and Bronze Age people who worked the site left no written records, but it is clear that they aligned the monument to the summer solstice. Stonehenge sits among many other ancient structures on the plain and is thought to be ceremonially linked with similar “henges” throughout southern England. Other megalithic structures associated with the solstice are scattered throughout the United Kingdom, Ireland, and much of northern Europe. Here in the U.S. we also find ample evidence of the importance of the solstice to Native Americans. Throughout the North American high plains are dozens of “Medicine Wheels” that once served as focal points for religious ceremonies and marking the seasons. In the American Southwest there are a number of petroglyphs and angled boulders that cast “spears” of light onto carved spiral patterns at the time of the solstice.
The passing of the solstice means that we now experience our shortest nights here in the Northern Hemisphere. Here in Washington we have a mere 5 hours and 8 minutes of true darkness between the end and beginning of astronomical twilight. Fortunately the week’s waxing Moon gives us a nice target for our telescopes during the evening hours. I often say that the Moon is “looked over, then overlooked” by many of today’s amateur astronomers, but it nonetheless remains one of my favorite targets for viewing on warm summer evenings. Even though Luna keeps the same face constantly turned in our direction, its features, frozen for eons of time, can always show a detail of light and shadow that make it worth the time to study them. I can safely say that each time I point my telescope at our nearest celestial neighbor I spot something that I had never noticed before.
The bright glow of Venus continues to be a fixture in the western twilight sky. You should be able to easily find the dazzling planet by around 9:00 pm local time, and she remains above the horizon for just over an hour before setting. Venus owes her brilliance to her highly reflective atmospheric clouds, which reflect about 65 percent of the sunlight that strikes them.
You will now find Mars plodding steadily eastward among the faint stars of the rather nondescript constellation of Cancer. If you have a pair of binoculars you can track his daily progress as he closes in on the star cluster known as the Praesepe or “The Beehive”. He will pass through the heart of the cluster early next week.
Saturn and Jupiter are steadily making their way into the evening sky. By the end of the week both planets rise before midnight, and should be well-placed for viewing during the early morning hours. The best time to view them is during the morning twilight hours; at 5:00 they straddle the meridian in the southern part of the sky.
|Messier 51, the "Whirlpool Galaxy" in Canes Venatici, with companion galaxy NGC5195
imaged 2021 May 8 from Mollusk, Virginia
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor and a Canon EOS Rebel T2i DSLR.
The Moon returns to the evening sky this week, waxing through her crescent phases as she springs up from the western horizon. Look for her very thin crescent close to bright Venus in the twilight of the evening of the 11th. Two nights later Luna passes near Mars to the east of the stars Castor and Pollux in Gemini. She ends the week near the bright star Regulus in the constellation of Leo.
New Moon occurs on the morning of the 10th at 6:52 am Eastern Daylight Time. This particular New Moon also produces one of the year’s two solar eclipses. This one will be an annular, or “ring of fire” eclipse, with the central path crossing the arctic regions from Hudson Bay to northwestern Greenland, then across the pole to eastern Siberia. Here in Washington the Sun will rise shortly after greatest eclipse, with about 70% of his disc covered by that of the Moon. As Old Sol rises higher the Moon will slip farther to the east, and the eclipse, such as it is, will end 45 minutes later. Locations farther north and east will have better views, but only the partial phases will be visible from the United States. Maximum obscuration will be visible from northern Minnesota and the Upper Peninsula of Michigan, but even at these locations the Sun is only partially obscured. As with any solar eclipse, I cannot over-stress the need for proper eye protection. If you observe with the unaided eye you can look safely for a few moments right at sunrise, but your best bet is to use a pinhole projector or “eclipse glasses” one the Sun climbs a few degrees. If you are using a telescope or binoculars, cover the objectives with an approved solar filter.
We are now entering the two-week “season” of phenomena associated with the summer solstice. We will see the year’s earliest sunrise here in Washington on the morning of the 14th, when the Sun peeks over the eastern horizon at 5:42 am EDT. By the time of the solstice itself Sunrise will be a minute later, but the times of sunset will continue to creep a bit later in the evening. We will see our latest sunset on the 28th, when Old Sol slips below the west horizon at 8:38 pm EDT.
The short nights of June offer a bounty of interesting celestial sights so long as you don’t mind the late start to full astronomical darkness. The first part of the evening sky hosts a number of fairly bright external galaxies which can be glimpsed from suburban locations with modest telescopes. Beyond the stars of Leo, Virgo, and Ursa Major lie thousands of these distant “island universes” at distances that boggle the imagination. Although they appear to be little more than featureless smudges in the eyepiece, in reality they shine with the combined light of hundreds of billions of stars. One of my favorites is Messier 51, the “Whirlpool Galaxy”, which lies just over three degrees southwest of Alkaid, the star that marks the end of the “handle” of the Big Dipper. A small telescope under dark skies will reveal two fuzzy swatches of light against a velvet background sprinkled with stars. Larger telescopes will begin to show a spiral structure to the larger of the two galaxies which led astronomers of the 19th Century to give it its name. It is one of the most photogenic galaxies in the sky, having been imaged by thousands of amateur astronomers, professionals, and the Hubble Space Telescope. The Whirlpool lies at a distance of about 31 million light-years and is thought to be about half the size of our Milky Way galaxy.
Venus continues to work her way eastward from the Sun as she traverses the stars of the constellation of Gemini, the Twins. You should be able to easily locate her bright glow about an hour after sunset, when she is around five degrees above the west-northwest horizon. The sharp sliver of the young crescent Moon lies just to the right of Venus on the evening of the 11th.
Ruddy Mars has now entered the seemingly blank area of the sky between Gemini and Leo. There’s actually a constellation there, Cancer the Crab, but it is hard to locate under urban skies. The Moon lies about four degrees northeast of the red planet on the evening of the 13th.
Saturn has finally cracked the evening sky barrier, rising before midnight in the southeast. Jupiter follows the ringed planet into the sky about an hour later. Your best view of them will still be in the wee morning hours, though, where you will find them due south at the onset of morning twilight.
|The Moon in HDR, imaged 2021 March 21, 00:55 UT from Alexandria, Virginia
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor, Canon EOS Rebel SL2 DSLR and 1.4X tele-extender.
HDR composite of 4 exposures, 1/250, 1/60, 1/15, & 1 seconds, ISO 400.
The Moon waxes toward her full phase this week, plunging southward along the ecliptic where she will meet up with the rising stars of summer. Full Moon occurs on the 26th at 7:14 am Eastern Daylight Time. May’s Full Moon is popularly known as the Flower Moon due to the abundance of wildflowers that bloom at this time of year. It is also known as the Milk Moon in ancient European traditions and as the Corn Planting Moon among several Native American cultures.
Early risers on the 26th will be able to see part or all of the first of two lunar eclipses, depending on their location. Here in the eastern US observers west of a line from Lake Ontario to the DelMarVa peninsula can see the Moon work her way into Earth’s penumbral shadow beginning at 4:46 am EDT. Luna’s eastern limb will begin to take on a greyish tint as she moves closer to the umbral shadow, which will occur at 5:44 am EDT. Unfortunately, here in Washington, Luna sets five minutes later! However, observers living farther west will get a progressively better show. Residents near the Front Range of the Rocky Mountains will see the Moon enter the total phase at 5:09 am MDT. The total phase of this eclipse only lasts about nine minutes, though, since the Moon passes very close to the northern edge of the umbral shadow. She will emerge from her partial phases for residents along the California coast at 5:52 am PDT. While most of us get short-changed by this eclipse, we will have a better view of the very deep partial lunar eclipse that will occur on November 19th. In that event 98 percent of the Moon’s disc will be in the umbral shadow, and all aspects of the eclipse will be visible from the entire nation.
The spring constellations are now prominent in the evening sky, but the growing Moon’s light begins to wash out all but the brightest of the season’s stars. Luna may be found northeast of the star Regulus, heart of Leo, the Lion, on the 19th, and by the 22nd she will have moved to the vicinity of Spica, brightest star in Virgo, goddess of the Harvest. Each of these constellations sport attractive double stars that will be near the Moon on those dates. North of the Moon on the 19th is the second-magnitude star Algieba, located in the Lion’s “mane”. Binoculars will show this star with a distinctive yellow cast. Just below it is the fifth magnitude star 40 Leonis. In a small telescope Algieba reveals itself as a fine pair of yellow-tinted suns nestled close together. The pair orbit their center of mass once every 500 years, and for the next century appear as widely separated as they can get. By the year 2321 they will be too close to resolve in most amateur telescopes. On the 22nd look a few degrees west of the Moon for another fine double star, Porrima. This pair consists of two nearly identical stars that orbit each other once every 169 years. The stars appeared closest together in 2005; at the time they were difficult to resolve in the Observatory’s 12-inch refractor. Since that time the gap between them has widened, and they are now easily split in my 4-inch telescope. This is one of the few pairs of stars that show perceptible changes in separation and position angle from year to year. Because the pair have such a well-studied orbit, we can deduce a number of their physical parameters.
The early evening sky continues to host Mercury and Venus in the twilight hour. Venus should be easy to spot if you have clear skies and a low western horizon. Half an hour after sunset on the 18th the dazzling planet will be about five degrees above the skyline, with much fainter Mercury about six degrees higher. Binoculars will help you locate Mercury in the twilight glow. By the end of the week Venus will have crept up on Mercury, while the latter begins his plunge toward the Sun. On the 25th they will be about three degrees apart. They will be closest together on the 28th, when they are a scant half-degree apart.
Mars is making his way eastward through the stars of Gemini, which can be seen prominently in the west as twilight ends. The red planet and the Twin Stars form a different triangle with each passing night. Mars will pass just over a degree north of the third-magnitude star Wasat on the 23rd and 24th.
Jupiter and Saturn are still best placed for viewing before sunrise, but they are making steady progress toward a fine evening show in the summer months. Saturn reaches the first stationary point in the current apparition on the 23rd. He will slowly begin to slink westward among the stars of Capricornus before resuming direct eastward motion in October. Jupiter shines down from the dim stars of Aquarius, dominating that part of the morning sky. He will begin his retrograde loop a month from now.
|Venus (above clouds) and Mercury, imaged 2021 May 9, 00:45 UT from Mollusk, Virginia
with a Canon EOS Rebel SL2 DSLR. HDR composite of 3 exposures, 34mm f/8, ISO 200.
The Moon returns to grace the evening sky this week, waxing to First Quarter phase on the 19th at 3:12 pm Eastern Daylight Time. This week offers one of the best opportunities to spot a very slender lunar crescent. On the evening of the 12th the 1.4 percent sliver of the Moon will be located just to the left of the bright planet Venus. At 8:45 pm you should be able to spot Venus about five degrees above the west-northwest horizon. Luna’s crescent should become apparent at around that time as well. Find a good site with an unobstructed view to the west to find this interesting pair. On the following evening the Moon should be easy to spot. Look a few degrees to the right of the Moon to find the elusive planet Mercury. On the night of the 15th you will find a dimming Mars just over two degrees northeast of Luna.
May 15th marks the annual spring observance of International Astronomy Day. This event, first celebrated in California in 1973, has grown into a world-wide effort on behalf of amateur astronomers to involve the public in their fascinating hobby. It is now held twice a year in the spring and fall on a Saturday near the time of the First Quarter Moon. Here in the Washington metropolitan area it has been promoted and staged by the Northern Virginia Astronomy Club (NOVAC) for many years, and takes place at C.M. Crockett Park near Midland, Virginia from 5:00 until 11:00 pm EDT. Cub members will be on hand to discuss telescopes, observing, and imaging techniques, and telescopes will be set up for visitors to view through. The event is open to the public, but non-Fauquier County residents must pay a nominal park fee. COVID protocols will be observed, so face masks will be required of all participants. More information is available on the NOVAC website.
This is one of those weeks where I hope for clear skies every night, as there is something for every level of interest to enjoy. The Moon coursing her way past the evening’s planets offers early evening skywatchers the treat of looking at the battered surface of another world nearly a quarter million miles away. Luna is a perfect target for binoculars and small telescopes, and as her crescent thickens from night to night new landscapes sweep into view. Luna sets by the late evening through most of the week, leaving a few hours of dark skies to view some of the other wonders of the springtime sky. At this time of year the “deep sky” is dominated by faint smudges of light that are the signatures of distant galaxies scattered among the stars of Ursa Major, Leo, Boötes, Coma Berenices, and Virgo. A four-inch telescope will reveal dozens of these “island universes”, most of which are tens of millions of light-years distant. It is also a time to start seeing so-called globular star clusters, which resemble luminous spherical puffs of smoke in the eyepiece. One of the most spectacular of these objects may be found in the constellation of Hercules, which is high in the east by 11:00 pm. The Great Hercules Cluster resolves into a myriad of faint stars in my 4-inch telescope, and increasing the aperture to 8-inches gives it the appearance of a luminous dandelion seed crown. These clusters are remnants of the cores of ancient dwarf galaxies that formed with our Milky Way some 13 billion years ago. Our much larger galaxy has stripped these star swarms of their star-forming dust and gas, leaving their primordial spherical cores to slowly orbit our galaxy’s massive central bulge.
As mentioned earlier, the Moon passes the innermost planets Venus and Mercury early in the week. Venus has just emerged from conjunction with the Sun and is gradually climbing above the western horizon. Elusive Mercury will reach his greatest elongation east of the Sun on the 17th, so he is at his best in the early evening sky right now and for the next couple of weeks.
Mars is plodding relentlessly eastward through the stars of Gemini, and he, too, gets a visit from the Moon on the 15th. The red planet now shows a tiny pink disc in the telescope, and he has faded to nearly second magnitude. He gradually pulls away from the third magnitude star Mebsuta as the week progresses.
Jupiter and Saturn still rise in the wee hours of the morning and are still best seen well before sunrise. You will find them on the southeastern sky as morning twilight begins. At this time both planets are high enough to give a good view in the telescope.
|Markarian's Chain, the heart of the Virgo Galaxy Cluster
imaged 2020 May 24, 03:20 UT from Mollusk, Virginia with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor telescope
and a Canon EOS Rebel T2i DSLR.
The waning Moon makes her way eastward through the dim rising constellations of autumn. New Moon occurs on the 11th at 3:00 pm Eastern Daylight Time. You will find Luna southeast of bright Jupiter on the mornings of the 5th and 6th.
This week we get a visit of sorts from one of the most famous members of the solar system, Halley’s Comet. We won’t actually see the comet itself; that last happened in 1986 and won’t happen again until 2061, but tiny pieces of the comet are now interacting with the Earth in the annual Eta Aquariids meteor shower. This display can produce a meteor every minute or two, and is best seen from the southern United States. The radiant is located near a small asterism known as the “Water Jar” that consists of a small triangle of 4th and 5th magnitude stars surrounding a central 3rd magnitude star. Observers at the latitude of Washington, DC have about two hours to get a good view before twilight begins to brighten the sky. If you miss this shower the Orionids of October are associated with another meteoroid stream from Halley’s Comet.
With the Moon’s absence from the evening sky it is time for the May campaign for the Globe at Night citizen science project. This month’s featured constellation is Boötes, the Herdsman, whose brightest star, Arcturus, is visible from any location in the Northern Hemisphere with an open view of the sky. Although Arcturus is easy pickings, the rest of the constellation is more obscure. The rest of the Herdsman is located to the east of the “handle” of the Big Dipper and resembles a kite or an ice cream cone. Most of the stars in the constellation are third magnitude and should be visible from the outer suburbs of major metropolitan areas. Making an observation is simple; just go to the Globe at Night web app and follow the instructions. So far this year the project has collected over 14,000 observations, well on the way to their goal of 20,000.
The short nights of late spring find a transition between the bright stars of winter and the rising stars of summer. Although the spring constellations don’t have the “pizzazz” of the brighter star patterns of spring and summer, it’s what’s behind them that makes this time of year special to dedicated skywatchers. The brighter stars are typically associated with constellations along the Milky Way, but at this time of year our home galaxy hugs the horizons. As we look upwards we are looking out of the galactic plane through a relatively thin distribution of stars. If you were to travel toward the center of the triangle bounded by Arcturus, the bright star Spica, and the “tail” of Leo, the Lion you would pass through our spiral arm of the Galaxy for about 1000 light years, then encounter a void of unimaginable dimensions. After a journey of some 35 to 40 million light years you would run into the outer members of a vast cluster of galaxies known as the Virgo Cluster. There are thousands of galaxies in this part of the sky, and many of them are visible in small telescopes. Under dark skies they float like ghostly wisps of light in the eyepiece, each one consisting of hundreds of billions of stars. The brightest members are gigantic elliptical systems sporting trillions of stars and enormous black holes in their cores. Their gravity is so powerful that our own Milky Way feels their influence! I have spent many pleasant spring nights chasing down hundreds of these wisps of light, and I still have several hundred more to find.
Back in our own cosmic back yard, planets are beginning to converge in the night. During evening twilight the elusive planet Mercury continues to shine low in the west-northwest as he climbs toward greatest elongation from the Sun at mid-month. Half an hour after sunset you should be able to spot him about 8 degrees above the horizon as the week begins, and he will climb a few more degrees before he starts to retrograde back toward the Sun.
Dazzling Venus should be visible to folks with flat horizons about five degrees below Mercury. She is set to gradually return to the evening sky, but her progress will be slow. She won’t set after the end of evening twilight until the end of August.
You’ll find ruddy Mars drifting eastward through the stars of Gemini, the Twins. The red planet isn’t very bright these days, but you should be able to find him in the west between the bright stars Procyon and Capella, under Castor and Pollux, the Gemini “twin stars”.
Jupiter and Saturn still grace the pre-dawn sky, beaming down from the faint constellation of Capricornus in the southeastern sky. Both planets should be easy to find if you happen to be up and about at 5:00 am.
|The Full Pink Moon, imaged 2021 April 27, 02:44 UT from Alexandria, Virginia
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor telescope, 1.6X Barlow lens,
and a Canon EOS Rebel SL2 DSLR.
The Moon dips into the southern reaches of the ecliptic this week, wending her way through the rising summertime constellations. Last Quarter occurs on May 3rd at 3:50 pm Eastern Daylight Time. Luna passes just over three degrees north of the ruddy star Antares on the morning of the 29th. Two mornings later she passes through the “top” of the “teapot” asterism in Sagittarius. Early risers on May 4th will find her in an attractive triangle with the planets Jupiter and Saturn.
May 1st marks another of the so-called “cross-quarter days” that were once incorporated into traditional agricultural calendars. These dates marked the mid-point of the astronomical seasons, but to many ancient cultures they represented seasonal beginnings. “May Day” is still observed in many parts of Europe, where the tradition has been handed down since Roman times. Its earliest incarnation was the Roman festival known as the Floralia, a day to honor the gods Dionysus and Aphrodite. As with many such celebrations it was observed over several days around May 1st and involved various forms of merrymaking. Its observance dates back to at least the First Century BCE, when Cicero mentioned his participation in the festival. Originally intended as a celebration of fertility, by the end of the First Millennium CE it had evolved into more of a religious festival. Early Christian Germanic people observed it as Walpurgisnacht, commemorating the canonization of the abbess Saint Walpurga on May 1, 870 CE. Celtic peoples observed the date as Beltaine, a night of bonfires, dancing, and leaping through fire to bless their cattle as they headed to high mountain pastures. Many of these traditions can still be found in modern May Day festivals. Feasting, the crowning of “May Queens”, and dancing around a May-pole are traditions that have persisted over the millennia.
As the Moon recedes into the morning sky this is probably your final week to get a good look at the last of winter’s constellations. The seasonal showpiece, Orion, begins to set at the end of evening twilight, and by the late evening all but the bright stars Capella, Castor, Pollux, and Procyon are left hanging in the west. He only star of spring that can rival the bright luminaries of winter. Arcturus is the brightest star in the Northern Hemisphere sky and is outshone by only three other stars, all of which are best seen from more southerly climes. It has a distinct rose-pink tint to my eyes, and this color betrays something about its nature. It is evolving toward the end stages if its life, and current estimates place it at an age of about 7 billion years, much older than our Sun’s 4.5 billion. It is slightly more massive than the Sun, so it gives us something of a preview of Old Sol’s ultimate fate. Arcturus is a “red giant” star, one that has exhausted the hydrogen in its core and now fuses hydrogen into helium in a core-surrounding shell. This, in turn, causes the star’s girth to expand; the diameter of Arcturus is about 25 times that of the Sun. As its surface area expands its radiative layer cools, giving it its characteristic reddish tint. Arcturus has probably been studied with large telescopes more than any other star except the Sun. Because it is so bright its light can be spread out into a highly detailed spectrum that reveals the chemical makeup of its surface layers and atmosphere. It is used as a standard calibration star for mapping the spectra of other stars. From its spectrum we can determine that it is moving in our direction at around 5 kilometers (three miles) per second. Don’t worry, though; its closest approach won’t happen for some 4000 years, and it will never get closer than about 36.6 light-years.
The bright planet Venus and the elusive Mercury share the limelight in evening twilight for the next few weeks. This week you will find them low on the western horizon about half an hour after sunset. Mercury puts some distance between the two as the week progresses, becoming a bit easier to see each passing evening. On the evening of the 3rd he passes just 2 degrees south of the Pleiades star cluster. You will want to use binoculars to see the cluster’s brightest stars.
Mars is now at his most northerly point in the sky, riding high among the stars of Gemini. He begins the week just to the northeast of the bright star cluster Messier 35, then marches resolutely eastward. He is now four full magnitudes fainter than he was at opposition last October, and observers in urban locations might have a little difficulty finding him. That said, his ruddy tint should betray his location southwest of Castor and Pollux.
Jupiter and Saturn continue wo work their way toward the evening sky, but they are still best seen in the hours before dawn. By the onset of morning twilight they should be easy to spot in the southeastern sky among the faint stars of Capricornus. The waning Moon joins them on the morning of the 4th. This should be a nice photo opportunity for early risers.
|Lunar composite, imaged 2021 April 20 01:31 UT from Alexandria, Virginia
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor telescope, 1.6X Barlow lens,
and a ZWO ASI224MC CMOS imager. 15 subframes stitched using AutoStitch software.
The Moon brightens the evening sky this week, waxing through her gibbous phases towards Full Moon, which will occur on the 26th at 11:31 pm Eastern Daylight Time. April’s Full Moon has a number of popular names associated with it, all indicators of the rejuvenation of the spring season. The most popular name is the Pink Moon, a tribute to the outburst of spring wildflowers throughout north temperate climes. Other names include the Hare Moon, Sprouting Grass Moon, Fish Moon, and Egg Moon. Look for the Moon nestled among the stars that form the “head” of Leo, the Lion, on the evening of the 21st. On the 25th you will find her just over five degrees north of the bright star Spica.
Fans of annual meteor showers have had to wait for several months to enjoy a decent display. After the Quadrantids peak in early January, the next major shower to look forward to is the Lyrids, which peak on the morning of the 22nd. These meteors appear to originate from a point in the sky near the small constellation of Lyra, the Harp, whose brightest star, Vega, forms one apex of the Summer Triangle asterism. You will find Vega rising in the northeast during the late evening hours, and under moonless conditions up to 20 meteors should be visible per hour beginning at around local midnight. Unfortunately, the waxing gibbous Moon throws a lot of light around the sky, so viewing the Lyrids this year will probably something of a bust. Take heart, though, meteor lovers; the next good shower, the Eta Aquarids, should be active in early May, and the Moon shouldn’t be a factor.
As the end of evening twilight slips later into the night the last of winter’s constellations slip inexorably toward the western horizon. This is the time of year when we can witness an ancient myth that has been re-enacted for millennia. The signature constellation of winter is Orion, who can be seen low in the west as twilight deepens. One by one his brighter stars wink out as they set, and the last one to do so is the distinctive red-tinted star Betelgeuse. In mythology, Orion was not only a masterful hunter, he was also something of a braggart. A son of Poseidon by the Gorgon Euryale, he boasted to Gaia, goddess of the Earth, that he could kill any animal that came his way. To punish him, Gaia dispatched a lowly scorpion that stung the Hunter on his foot. Eventually both were placed in the sky, but in such a way that they would never be seen together. Indeed, the star Betelgeuse sets about 15 minutes after Antares, the ruddy heart of Scorpius, rises. It is interesting to note that these two stars are physically very similar. Each is a highly evolved “red supergiant” that is nearing the end of its cosmic life. These stars fuse elements in a series of shells that surround the core. The byproduct of fusion of the innermost of these layers is iron, which has the most stable nucleus of all of the elements. No matter if you try to fuse it or split it, you need to put more energy into the reaction than you get out of it, so the star’s core effectively becomes a large heat sink. Some time in the next few hundred thousand years these stars will implode on their iron cores, liberating a fantastic amount of energy in a supernova explosion. Which one will go first? It’s anybody’s guess.
By the end of the week we welcome the return of two planets to the evening sky. The elusive Mercury and the effusive Venus can be glimpsed just above the west-northwest horizon about half an hour after sunset. You will need a good flat horizon to see them, but they should be fairly easy to spot. Venus will be the brighter of the two, while Mercury will be just to the northwest of Venus. Mercury will continue to be visible for the next several weeks as he enters his best evening apparition for the year.
Mars continues to diligently forge eastward along the ecliptic. This week he moves into the constellation of Gemini, the Twins. On the evening of the 26th he may be found half a degree north of the galactic star cluster Messier 35. Despite the light of the Full Moon, owners of small telescopes should get a good view of this interesting cosmic meet-up.
You will still find Jupiter and Saturn lurking in the southeastern pre-dawn sky. Both planets are now ensconced in the dim constellation of Capricornus, the Sea-goat, so you shouldn’t have any problems locating them if you are up before the Sun.
|Lunar craters Hyginus (upper center) and Triesnecker, imaged 2021 March 22 from Alexandria, Virginia
with a Celestron 23.5-cm (9.25-inch) f/10 Schmidt-Cassegrain telescope, 1.6X Barlow lens, and a ZWO ASI224MC imager.
Note the craterlets in Hyginus Rille and the stress fractures around Triesnecker.
The Moon returns to the evening sky this week, waxing through her crescent phases as she moves along the northern extremities of the ecliptic. First Quarter occurs on the 20th at 2:59 am Eastern Daylight Time. Luna passes five degrees north of the star Aldebaran in Taurus, the Bull on the evening of the 15th. Over the following two nights she brackets the fading ruddy glow of Mars. She ends the week among the faint stars of Cancer, the Crab, just over three degrees northeast of the binocular star cluster Messier 44, commonly called The Praesepe or The Beehive.
This should be another fine week to check out the surface of our nearest neighbor in space. The Moon’s high northerly declination means that her light passes through a minimal portion of Earth’s atmosphere, and thus Northern Hemisphere observers can glean lots of detail through their telescopes. Milder evening temperatures also mean that a telescope’s optics reach thermal equilibrium more rapidly, further enhancing performance. This is the best time to look for subtle details under relatively high magnification. One of my favorite areas of Luna’s surface will be ideally placed for viewing on the evening of the 19th. Near the center of the Moon’s disc, just west of the terminator, look for what will look like a hairline crack with a crater near the middle. The crater, which has no upraised rim and sports a flat bottom, is named for the Roman astronomer Gaius Julius Hyginus, who wrote one of the first astronomical works to be printed with moveable type. The manuscript for his Poeticon Astronomicon was probably written in the first century BCE and describes the lore behind many of the “classical” Greek constellations. One of the treasures of USNO’s Library is a 1482 edition of this book.
The area around Hyginus crater is subjected to strong tidal forces caused by the Earth that stress Luna’s crust, so the area is criss-crossed with a number of these so-called “rilles”. Most of these look like cracks on an egg shell, but on nights of steady “seeing” you will notice that the Hyginus Rille is lined with a series of small craters that appear to be volcanic in origin. This is one of the few areas on the Moon where volcanism played an important role in shaping the local topography.
The winter constellations continue to slide westward as evening twilight creeps later each evening. By the late evening the springtime constellations are in firm control of the night. High in the south is the crouching figure of Leo, the Lion, led by the bright star Regulus. Turn to face the north and the seven stars that form the “Big Dipper” asterism are reaching their upper culmination. To the east is the rose-hued glow of Arcturus, which will dominate the sky for the next couple of months. While the outlines of Leo and the Big Dipper shouldn’t be too hard to trace out, the constellation associated with Arcturus is another matter. Gaius Hyginus would have you believe that these stars represent the figure of a herdsman holding two dogs on leashes as he guides the Great Bear and Little Bear around the celestial pole. To put it mi8ldly, I have trouble with this. However, the stars that make up Boötes do outline an acceptable ice-cream sugar cone, with Arcturus at the tip.
Mars gets a visit from the Moon on the 16th and 17th, but other than that he doesn’t have many friends from the solar system to pal around with. He continues to drift eastward from the “horns” of Taurus, and next week he will enter the constellation of Gemini, the Twins.
Both Jupiter and Saturn should now be easy to spot in the pre-dawn sky. Saturn rises first, coming over the horizon at around 3:30 am EDT, with Old Jove following some 45 minutes later. Jupiter is slowly moving east of Saturn, and will continue to do so until he starts his retrograde loop around the time of the summer solstice.
|Ursa Major under dark skies, imaged 2019 March 17 from Mollusk, Virginia
with a Canon EOS Rebel SL2 DSLR, 24mm f/2.8 EF-S lens @ f/4, and an Omegon Mini-Trak LX2 mechanical star tracker.
The Moon plays hard-to-get this week, waning in the early morning sky as the week opens and re-appearing in evening twilight as it ends. New Moon occurs on the 11th at 10:30 pm Eastern Daylight Time. Look for Luna a few degrees below bright Jupiter in deep twilight before dawn on the 7th. If you have a flat western horizon and a good, clear sky you might be able to catch a very slender crescent Moon half an hour after sunset on the evening of the 12th. She will only be about 22 hours past New Moon, so her crescent will be little more than a hairline. She should be much easier to spot on the following evening.
This week we celebrate International Dark Sky Week, a time when people are encouraged to turn out their outdoor lights to enjoy the beauty of the night sky overhead. The event was founded in 2003 by a Virginia high-school student, Jennifer Barlow, who wanted to try to encourage her neighbors to turn down their nighttime lighting. The event quickly became a national effort through the encouragement of the International Dark Sky Association, and in 2009 it became a world-wide event in celebration of the International Year of Astronomy. It is now not only sanctioned by IDA, but it is actively encouraged by the American Astronomical Society and the International Astronomical Union, the two largest organizations of professional astronomers. Its goals are simple. As Jennifer put it, "The night sky is a gift of such tremendous beauty that should not be hidden under a blanket of wasted light. It should be visible so that future generations do not lose touch with the wonder of our universe. It is my wish that people see the night sky in all of its glory, without excess light in the sky as our ancestors saw it hundreds of years ago." The negative effects of light pollution began to receive attention from the astronomical community in the 1980s. Since that time many studies have shown that it is more than just a nuisance to stargazers. It affects many ecosystems in detrimental ways, with dire effects on bird and animal migrations and breeding cycles as well as human circadian rhythms and physical health. In addition, it consumes vast amounts of energy from fossil fuels, most of which is wasted in lighting up the sky and adds to the already high concentrations of carbon in our atmosphere. It is the goal of International Dark Sky Week to draw attention to this issue, which can easily be reversed for everyone’s benefit. Please dim your lights and enjoy the nights!
Spring’s constellations greatly benefit from dark skies. Unlike the bright stars of winter, which lie along the plane of the Milky Way, the stars of spring lie in the direction of the galactic pole. Essentially our line-of-sight passes through the thin disc of our home galaxy, so we see relatively few bright stars. With a handful of exceptions most of the spring constellations’ outlines are “fleshed out” by third- and fourth-magnitude stars. A case in point is the constellation of Ursa Major, the Great Bear. Most of us can see the seven stars of the Big Dipper asterism, but they make up less than half of the constellation’s shape. From a dark site, though, the rest of the Bear takes shape, from her triangular head to her long legs terminating in claws. One of my favorite spring constellations can only be seen under good dark sky conditions. To find it first locate the sickle and triangle that make up the constellation of Leo, the Lion. Just to the east of Denebola, the star that marks the Lion’s tail, you will find a large scattering of faint stars that represent Coma Berenices, or “Berenice’s Hair”. This is the only constellation named for an historic figure and represents the golden tresses sacrificed by Berenice II, Queen of Egypt, for the safe return of her consort, Pharaoh Ptolemy III, from battle.
Planet Mars continues his lonely eastward trek through the setting stars of winter. This week he continues his journey across the stars of Taurus, the Bull. By the week’s end he passes between the stars El Nath and Zeta Tauri, which mark the tips of the Bull’s horns.
Saturn and Jupiter now rise before the onset of morning twilight, and may be found low in the southeast as the sky begins to brighten. Saturn leads Old Jove by about half an hour and lingers even as Saturn winks out in the increasing twilight glow.
|Messier 81 (bottom) and 82, galaxies in Ursa Major, imaged 2021 March 7 from Turner Mountain, Virginia
with a 10.2-cm (4-inch) f/6.5 Explore Scientific AR102 refractor and a Canon EOS Rebel T2i DSLR
The Moon wanes as she wends her way along the southern reaches of the ecliptic this week. Last Quarter falls on April 4th at 6:02 am Eastern Daylight Time. You will find Luna carousing with the rising summer constellations of Scorpius and Sagittarius in the pre-dawn sky. On the morning of the 6th look for pale yellow Saturn just over four degrees north of the Moon. On the following morning Luna’s slimming crescent will pass a similar distance south of bright Jupiter.
I’m sure that you have all heard the expression, “March comes in like a lion and goes out like a lamb”. Indeed, early March is when the constellation of Leo, the Lion becomes prominent in our sky, and by the month’s end the constellation of Aires, the Ram disappears into evening twilight. Leo figures prominently in our upcoming evening skies as it is the focus on the April campaign for the Globe at Night citizen-science observing project, which runs from the 3rd to the 12th. Leo’s brightest star, Regulus, is well up in the southeastern sky by 9:00 pm local time, and traditionally marks the site of the Lion’s heart. From a suburban location you can see a semi-circular asterism above Regulus that resembles a backwards question mark that is popularly known as “The Sickle”. This grouping forms the Lion’s head. Some 15 degrees east of Regulus is a right triangle of stars that denote the Lion’s hindquarters. To participate in the Globe at Night project, simply go outside, let your eyes adapt to the dark for 15 to 20 minutes, then compare the number of stars that you see to the charts on the Globe at Night web app. Your observation will benefit scientists researching the effects of nighttime outdoor lighting and its effects on the environment.
Leo represents the Nemean Lion, slain by Heracles (the Roman Hercules) as the first of his Twelve Labors. It holds a number of treats for owners of small and modest-aperture telescopes. One of my favorite targets is the yellow-hued star Algieba, which lies about 8 degrees north of Regulus. Through binoculars the golden tint of the star becomes readily apparent, and pointing a small telescope towards it reveals that Algieba is a beautiful close binary star system. In my 4-inch refractor the stars glow with a deep yellow cast like a distant pair of cat’s eyes. Under darker rural skies larger telescopes reveal faint smudges of light interspersed among Leo’s stars. These fuzzy wisps are actually distant galaxies, far removed from the constellation’s stars. While Regulus shines from 77 light-years away, the constellation’s brighter galaxies shine across a gulf of 20 to 40 million light-years of space!
Leo begins to cross the meridian at around 11:00 pm local time. If you pivot 180 degrees and look toward the north you will encounter the seven-star asterism known as the Big Dipper. These are the most prominent stars of the constellation of Ursa Major, the Greater Bear, which occupies much of the northern part of the sky at this time of year. The five middle stars of the Dipper share a common proper motion through space, and thus seem to be part of a very loose galactic cluster that is currently about 80 light-years from us. Thirteen stars have been positively identified in the Ursa Major Moving Group, and there may be as many as two dozen more that may be members scattered across the sky. Like Leo, the stars of Ursa Major lie in front of many external galaxies, making this a prime hunting ground for amateur astronomers with big telescopes.
Lonely Mars spends the week drifting eastward between the stars that form the tips of the horns of Taurus, the Bull. Over the next several weeks the red planet will form a constantly-shifting triangle with two other red stars, Aldebaran and Betelgeuse. Look for them in the west as evening twilight fades.
Jupiter and Saturn are still best seen in the gathering morning twilight, low in the southeastern sky. Jupiter is by far the brighter of the pair and follows Saturn’s rise by about half an hour. You will have some nice photo opportunities to snap each one with the waning Moon as the week ends.
|Annotated Gibbous Moon, imaged 2019 October 10 from Shoestring Observatory, Alexandria, VA
with a 10.2-cm (4-inch) f/6.5 Explore Scientific AR102 refractor, TheleVue 2X Barlow lens, and a Canon EOS Rebel SL2 DSLR
The Moon descends from her high declination this week as she brightens the sky surrounding the springtime constellations. Full Moon occurs on the 28th at 2:48 pm Eastern Daylight Time. The March Full Moon is popularly known as the Worm Moon, Crow Moon, or Sap Moon, as all of these mark the warming of the ground as winter loses its grip on the Northern Hemisphere. It is also the Paschal Moon for Christians, setting the date for their most important feast day, Easter. For Jews, the Full Moon marks the date of 15 Nisan in the Hebrew calendar, the traditional beginning of the weeklong observance of Passover. Look for the Moon near the bright star Regulus on the evening of the 25th. She rises with the star Spice on the 28th and 29th.
The first few nights of the week offer yet more good views of the Moon through the telescope. As Luna waxes through her gibbous phases, the vast lava plain known as Oceanus Procellarum, the “Ocean of Storms”, gradually reveals itself as the terminator line slowly creeps westward from night to night. This feature, the only “ocean” on the Moon’s near side, is the largest formation of its kind on Luna’s surface, covering about 10 percent of her entire surface area. Unlike the other lunar “seas”, it does not have a defined circular shape, and its origins remain something of a mystery. It is noted for many “ghost” craters that have been flooded by lava over the eons, but it also has some of the most distinctive craters to be found on our natural satellite. The prominent crater Copernicus is well placed on the evening of the 23rd, just to the south of the broken mountain ring that defines the edge of Mare Imbrium, the “Sea of Rains”. This crater would have been the landing site for Apollo 20 had that mission not been cancelled in 1972. Apollos 12 and 14 landed in Oceanus Procellarum, touching down in a small “bay” that had also been visited by the American Ranger 7 and Surveyor 3 missions several years earlier. All of this activity has caused this area of the Moon to be officially named Mare Cognitum, the “Known Sea”. On the evening of the 25th look for a small but very bright crater at about the “10 o’clock” position on the terminator. This is the crater Aristarchus, one of the brightest and youngest features on the lunar near side. “Young” in this case is a relative term as the crater is believed to have formed some 400 million years ago! Just to the west of Aristarchus is the flat-bottomed crater Herodotus and the curious feature known as the “Cobra Head”, believed to be a collapsed lava tube. Careful scrutiny of this area on a night of steady air will show several more such “rilles” and the half-flooded crater Prinz.
As winter’s stars heel over to the west, the bright beacon of the star Arcturus becomes more prominent in the east. To me this star has always been symbolic of spring with its rose-tinted glow. You won’t have any trouble finding it despite the bright light of the Moon, but tracing out the rest of the star’s parent constellation is a bit more tricky. Arcturus leads a group called Boötes, the Herdsman and is supposed to represent a shepherd with two dogs on leashes guiding the Great Bear and Little Bear around the pole star. This takes a dark sky and considerable imagination to make out, but I find it easier to recognize as an ice-cream cone, with Arcturus marking the tip, a much more seasonal asterism!
Mars continues his easterly trek among the stars of Taurus, the Bull. This week the red planet passes north of the star Aldebaran, and by the end of the week he forms a line with Aldebaran and the star El Nath, which marks the tip of the Bull’s northern horn.
Jupiter and Saturn should now be pretty easy to find low in the southeastern sky about an hour before sunrise. The two giant planets have moved into the obscure constellation of Capricornus, and will become more prominent in the evening sky as summer approaches.
|The Moon, imaged 2018 February 20, 23:30 UT from the U.S. Naval Observatory, Washington, DC
with the 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor and a Canon EOS Rebel SL2 DSLR.
The crater Theophilis is arrowed.
The Moon brightens the evening skies this week, waxing through her crescent phases as she climbs northward along the ecliptic. First Quarter falls on the 21st at 10:40 am Eastern Daylight Time. Look for Mars about two degrees northwest of the Moon on the evening of the 19th. By the end of the week she beams down from the vicinity of the Gemini twins, Castor and Pollux.
This is the best time of the year to get to know our nearest natural satellite. For Northern Hemisphere observers the Moon reaches her highest declination as she approaches first quarter, which means that we won’t be looking through as much of our atmosphere during her most favorable phases for viewing. Exploring Luna’s surface is one of my favorite activities which I can enjoy from the confines of my suburban front yard. There’s no need to load up the telescope and drive to a remote site away from the city; the Moon sheds ample light for exploration from almost anywhere. During this week the terminator line slowly advances from night to night, revealing new landscapes to delight the viewer. On the evening of the 18th the terminator crosses the large impact crater Theophilus, which lies just south of the Moon’s equator. This feature has a very prominent central peak, which will cast a long, opaque shadow over the crater floor. This feature was formed by the impact of a modest-sized asteroid some 2 billion years ago that left a crater just over 100 kilometers (60 miles) across and some 4500 meters (13,500 feet) deep. That’s almost as big as the island of Hawai’i and as deep as that island’s Mauna Kea is tall. As the terminator advances it reveals that Theophilus lies atop an older, similar sized crater, Cyrillus. Both of these craters lie along the eastern edge of Mare Nectaris, the Sea of Nectar, which is one of the smaller lunar “seas” on the Earth-facing side. If the air is very steady look for the dozens of small craterlets that dot the Mare’s surface; these are “secondary” craters formed when material blasted from the impact that formed Theophilus subsequently fell back and impacted the hardened lava plain.
As the groundhog predicted way back in February, the vernal equinox arrives on the 20th at 5:37 am EDT. At this moment the center of the Sun’s disc stands directly over the Equator about halfway between Africa and South America. More importantly, it defines the beginning of astronomical spring. That said, the date when we actually have “equal night” occurs on the 17th since the Sun subtends a tangible disc. From that day until September 25th the duration of daylight will be longer than that of night.
Few people actually like the change from Standard to Daylight Time, but one good effect that it has is that it seemingly prolongs the appearance of Orion and his cohort of bright winter stars for the backyard astronomer. I can set up my telescope after dinner now and still have time to peruse these constellations and enjoy some of their interesting treasures. The Orion Nebula is always a treat to see, even from urban yards, and there are a wealth of fine star clusters to look for if you sweep from Capella to Sirius on the eastern side of Orion. These star clusters become less prominent in the later spring skies as the Milky Way sets to the west. They will be replaced by distant galaxies as we gaze out of the Milky Way’s plane.
Lonely Mars continues his eastward trek through the stars of Taurus. dimmer than the nearby star Aldebaran. During the course of the week Mars passes about seven degrees north of the star. The pair are joined by the nearly first quarter Moon on the evening of the 21st.
Jupiter and Saturn are now becoming easier to see in the glow of morning twilight. Saturn rises at around 5:00 am by the end of the week, with Jupiter following half an hour later. Look for both planets low in the southeast about 45 minutes before sunrise.
|Orion, the Hyades, Mars, and the Pleiades, imaged 2021 March 7 (UT) from Turner Mountain, Virginia
with a Canon EOS Rebel SL2 DSLR, EF-S 18-55mm f/3.5-5.6 zoom lens @ 18mm f/4, and
an Omegon MiniTrak LX2 manual star tracker
The Moon plays hard-to-get this week as she skirts the southeast horizon before dawn, then returns to the early evening sky by the week’s end. New Moon occurs on the 13th at 5:21 am Eastern Standard Time. If you have a clear view to the southeast, look for Luna with the rising planets Jupiter and Saturn before dawn on the 10th. By the end of the week you can find her waxing crescent low in the southwest as evening twilight fades.
It is once again time to exercise the annual spring ritual of setting our clocks ahead by one hour, “springing forward” to Daylight Time at 2:00 am on the morning of the 14th. Love it or hate it, it’s the law of the land as specified in U.S. Code, Title 15, Chapter 6, Sub-chapter IX – Standard Time, and it has been thus codified (with several amendments) since 1918. The provision for advancing our clocks dates to that year in an effort to help factories extend their most productive day shifts to maximize wartime demands. Although it seemed like a logical idea at the time, Daylight Time proved to be so unpopular that the provision for it in the law was repealed a year later. It remained a matter of state and local jurisdictions to invoke Daylight Time until World War II, when it was permanently reinstated as “War Time” by an act of Congress. From February 9th, 1942 until September 30th, 1945 the nation observed year-round Daylight Time. After the war the decision to advance clocks once again became a local matter, but in 1966 it was re-established in U.S. Code. The rule as it exists today was enacted in 2005. While the U.S. Naval Observatory is charged with providing the nation’s reference time-scale, it is not within our scope to enforce the law on how time is observed. That distinction belongs to the Department of Transportation.
You still have a few more evenings of early sunsets to make observations of the constellation of Orion for the benefit of the Globe at Night project. The Hunter is still prominent in the early evening sky, and you can make your observations under fully dark skies by 8:00 pm. Participation is easy; just follow the steps on the Globe at Night website.
The March sky is one of transition from the bright beacons that illuminated the long nights of winter to the more solitary bright stars of spring. As Orion and the stars of the Great Winter Circle heel over to the west, look toward the northeast for the rising stars of Ursa Major, the Great Bear. The seven brightest stars of this constellation for the familiar asterism of the Big Dipper, and while they don’t have the dazzle of Orion’s stars they do form a pattern that almost every Northern Hemisphere skywatcher knows by heart. In the early evening the Dipper seems to be balanced on its “handle”, but as the night passes it revolves westward over the north celestial pole. If you follow the arc of the stars that form the “handle” you will come to the brightest star in the northern hemisphere sky, Arcturus. Sighting this star has always been a sure sign of spring to me, and its cheery rosy tint reminds me that warmer days and nights are coming. Arcturus beams at us from about 37 light-years away, and it is the closest “red giant” star to the solar system. While it is slightly more massive than our Sun, it has begun to evolve toward its eventual demise as it exhausts the hydrogen fuel in its core, giving us a glimpse of Old Sol’s fate in another 2 billion years.
Our sole evening planet is Mars, which spends the week moving through the stars of Taurus, the Bull in the western sky. The red planet will glide to the north of the bright star Aldebaran as the week progresses, leaving the Pleiades star cluster in his wake. At around 8:30 pm local time you will have a fine view of three red objects in this part of the sky, giving you the chance to examine Betelgeuse in Orion, Aldebaran, and Mars in the same field of view.
Jupiter and Saturn reveal themselves just after the start of morning twilight in the southeastern sky. The two planets swapped positions with each other in a spectacular conjunction late last December, so Saturn now leads Jupiter over the horizon. Both planets will be hard to spot without a good view to the southeast, but they will become more prominent as we move deeper into spring.
|Orion & Sirius, 2020 January 1, imaged from Mollusk, Virginia
with a Canon EOS Rebel SL2 DSLR, EF-S 18-55mm f/3.5-5.6 zoom lens, and
an Omegon MiniTrak LX2 manual star tracker
The Moon dives southward along the ecliptic this week, mingling with the spring constellations and the first rising stars of summer. Last Quarter falls on the 5th at 8:30 pm Eastern Standard Time. Early risers can catch Luna among the stars of Scorpius, just north of the bright star Antares, before dawn on the 5th. As the week ends the Moon closes in on a gaggle of planets lying low over the southeast horizon as twilight begins to brighten the sky.
The March citizen-science observing campaign for the Globe at Night project kicks off on the evening of the 5th and runs through the 14th. 2020 was a record year for the program, which began in 2006. Over 29,000 observations were reported from observers around the world, and over the years the program has had responses from people in 180 countries. Part of the program’s success last year can be tied to the coronavirus, which has prompted many people to seek outdoor activities near their homes. There has been a “boom” in interest in amateur astronomy as people realize that being quarantined doesn’t limit you to your home when the universe is literally over your head every clear night.
Participating in Globe at Night is very easy. Find the month’s featured constellation, go outside and let your eyes adapt to the darkness, then compare your view of the sky with the charts posted on the Globe at Night website. This month’s featured constellation is Orion, which can be seen from every inhabited part of the planet. The Hunter’s bright, distinctive pattern is almost universally recognized, and his outline can be seen from just about any location including the centers of major cities. Your report to the website will help scientists determine the amount of light (and wasted energy) is escaping our planet into space.
Orion is well-placed in the early evening, just west of the meridian at 8:00 pm local time. He is perhaps my favorite constellation because of his distinct shape and the colorful bright stars that delineate him. He is a real treat for owners of small telescopes which accentuate the ruddy glimmer of Betelgeuse and the icy blue of Rigel and the “Belt Stars”. Just below Orion’s belt is a small gathering of stars that are easy to spot in your telescope’s finder. The middle “star” in this clump marks the location of the Great Orion Nebula, one of the few “deep sky” objects that can be seen well from urban locations. The nebula appears as a softly glowing cloud surrounding a group of four stars known as the Trapezium. These stars are very young and very energetic. Most of their radiation falls in the ultraviolet portion of the spectrum, and this radiation causes the gas in the surrounding nebulosity to glow. Above and below the nebula are other loose clusters of stars that glimmer like tiny diamonds against the inky background.
Following Orion across the sky is Canis Major one of his two hunting dogs. This grouping boasts the brightest star in the night sky, Sirius. Although the star’s name is derived from the Greek word for “scorching” it is popularly known as the Dog Star. Watching it drift through the telescope field is a bit like watching a mini-sunrise. The field begins to brighten as the star draws nearby, then bursts with an explosion of bright blue light when it enters. Scintillation caused by air currents often makes Sirius dance through the colors of the rainbow, flickering like a distant candle.
Lonely Mars is still the only bright planet in the evening sky. He continues to drift eastward through the sky against the background stars of Taurus, the Bull. He is now a tad dimmer than the nearby star Aldebaran, and he spends the week passing between the star and the Pleiades star cluster. This should present a fine photo opportunity for novice astrophotographers.
If you’re willing to get up before the Sun, three planets will greet you in morning twilight. Saturn, Jupiter, and Mercury all gather in the southeast, but you will need a good flat horizon and very clear skies to glimpse them. The best time to look for then is at the end of the week, when the waning crescent Moon joins them on the mornings of the 9th and 10th. If you can spot Jupiter on the morning of the 5th you will find Mercury close by to the left of the giant planet.
|Location of Jezero Crater on Mars, based on map made during opposition October-November 2020
with a Celestron 23.5-cm (9.25-inch) f/10 Schmidt-Cassegrain telescope, 2.5X TeleVue Barlow lens,
and a ZWO ASI224MC color imager.
The Moon waxes in the evening sky this week, reaching her First Quarter phase on the 19th at 1:47 pm Eastern Standard Time. During the week Luna climbs rapidly northward along the ecliptic, placing her in ideal observing conditions for Northern Hemisphere residents. On the evening of the 18th she may be found a few degrees south of ruddy Mars. On the following night you will find her placed evenly between the bright star Aldebaran and the Pleiades star cluster in the constellation of Taurus, the Bull. The Moon ends the week close to Castor and Pollux, the Twin Stars of Gemini.
While the Moon may appear to be close to Mars on the 18th, that day will also see the arrival of the latest emissary from Earth. Last week a pair of space probes slipped into orbit around the red planet. The Hope orbiter, sponsored by the United Arab Emirates, arrived on the 9th, while the next day the ambitious Chinese Tianwen-1 mission settled into orbit as well. On the 18th the American Perseverance roving vehicle will arrive for a direct entry and landing on the martian surface. Perseverance is the successor to the Curiosity rover, which touched down on Mars on August 5th, 2012 and is still going strong. Like Curiosity, Perseverance is powered by a nuclear generator and is about the size of a small SUV. It carries a battery of cameras and other instruments to analyze the soil of its target site, Jezero crater, which is believed to be an ancient lake bed that formed early in Mars’ geological past. Perseverance will also collect samples of rocks and soil that will be left for a future lander to pick up and return to Earth. In addition to these ambitious goals, the rover will also deploy the first flying drone on Mars, a small solar-powered helicopter dubbed “Ingenuity”. The landing will take place at around 3:00 pm EST. “Live” coverage will be streamed on NASA TV, but you won’t actually see events occur in real time. Due to the distance between Earth and Mars communications from Perseverance will take over 11 minutes to travel to us at the speed of light. The mission will either succeed or fail four minutes before we endure the “seven minutes of terror” that make up the entry, descent, and landing phases of the flight.
As we reach out to virtually “touch” the surface of Mars, you can use this week to explore the varied surface features of our own natural satellite, the Moon. The evenings before and after First Quarter are my favorite times to bring the Moon closer via my telescopes. The stark beauty of the Moon can be appreciated with just about any optical aid, but I am partial to smaller instruments which tend to be less affected by the unsteadiness of our atmosphere. A good four-inch aperture telescope will reveal an astonishing array of features from night to night as the terminator line slowly creeps across Luna’s face. It is often said that the Moon is “looked over, then overlooked” by novice amateur astronomers, but she is well worth spending the time to give her close scrutiny. While her major features have been frozen in time for hundreds of millions of years, it is still possible to see something new at each lunation as the play of sunlight and shadow highlight old familiar features in new ways. That’s why I have come back to look at her each month for decades.
As we’ve mentioned, Mars is undergoing an invasion of sorts from the denizens of Earth. The red planet has piqued our curiosity for centuries ever since the first crude sketches of surface features were secured by the astronomer Christiaan Huygens in 1659. The planet comes to opposition every 2.14 years on average, presenting us with our best chances to observe his dusty surface from Earth. His most recent opposition in October 2020 saw him briefly shine as the brightest planet in the sky after Venus. He has now faded as Earth leaves him behind and is now prominent only because he is located in a sparsely populated part of the sky.
|Messier 37, open cluster in Auriga, imaged from Great Meadow Park, Old Tavern, Virginia on 2017 December 17
with an Explore Scientific AR-102 10.2-cm (4-inch) f/6.5 refractor and Canon EOS Rebel T2i DSLR.
The Moon returns to the evening sky by the week’s end. New Moon occurs on the 11th at 2:05 pm Eastern Standard Time. Try to spot Luna’s hairline crescent during evening twilight on the evening of the 12th. Over the next few evenings look for the phenomenon called “earthshine”, where the part of the Moon’s disc that’s not in direct sunlight reflects light from our home planet. This ghostly blue glow is best seen during the early crescent lunar phases.
We are now approaching the time of year when the length of daylight changes most rapidly. By the end of the week the Sun sets an hour later than it did back in December and sunrise occurs half an hour later than it did in early January. Each passing day brings about 2.5 minutes’ more daylight, and that rate will gradually increase until the vernal equinox on March 20th, when it will amount to over three minutes per day.
We see this change reflected in the night sky as well. The stars of the Great Winter Circle cross the meridian between 7:30 and 10:00 pm making way for the first of spring’s star patterns. You still have lots of time in the early evening to enjoy the colorful stars of winter and the many subtle treats that lie behind them. This is a great part of the sky to explore with binoculars, with many objects to delight both urban and rural skywatchers. High in the west you will find the famous Pleiades star cluster, a small knot of stars that has been the subject of lore and legend for civilizations across the millennia. To the naked eye in a dark site it looks like a tiny version of the “Big Dipper”, with six of seven stars typically visible. Binoculars begin to reveal the true nature of this group as dozens of fainter stars come into view. Modern astronomical techniques have identified over 1000 stars as members of the cluster. It is located about 440 light-years away.
Our next binocular target is easily found among the stars of Orion. Just south of the Hunter’s “belt” of three stars you will see a small asterism known as “The Sword”. Point your binoculars at the middle star in this group and you will see the wispy light of the Great Orion Nebula. This glowing cloud is a stellar factory that has spawned most of the bright blue stars that make up Orion’s familiar shape. Easily seen from suburban yards, the view from a darker site is even more spectacular. The nebula is surrounded by ice-blue stars set on a velvet background filled with faint shimmers of nebulosity. It 8is about 1300 light-years away.
From a dark site you should be able to see the subtle star-clouds of the Milky Way just to the left of Orion. Let your gaze follow the glow to the zenith and the bright yellow star Capella in the constellation of Auriga, the Charioteer. Sweep the area between Capella and the constellation’s second-brightest star El Nath (which also marks the tip of Taurus’ northern “horn”). Here you will find three bright star clusters that will just begin to resolve in your binoculars. Known as Messier 36, 37, and 38, these rich clusters lie at distances from 3500 to 4500 light-years. They are excellent targets for small telescopes, especially M37, which resolves into hundreds of stars.
Our final binocular stop is yet another star cluster that is located in the somewhat obscure springtime constellation of Cancer, the Crab. This group of faint stars resides between Castor and Pollux in Gemini and Regulus in the constellation of Leo, the Lion. By 11:00 pm Cancer is near the meridian; sweep the area halfway between Pollux and Regulus with your binoculars to locate a scattered group of stars that form the cluster known as the Praesepe, or The Beehive. In binoculars the cluster is a pleasing sight, set between four brighter stars. You should be able to see a few dozen stars in the cluster from a dark site
Lonely Mars continues his vigil in the evening sky. You will find him just over 10 degrees west of the Pleiades, and during the course of the week he closes in on the cluster. He won’t be lonely for very long, as three emissaries from Earth arrive over the next several days. Space probes from the United Arab Emirates, China, and the U.S. arrive between now and the 18th.
|Aldebaran, The Hyades, & The Pleiades, imaged from Mollusk, Virginia on 2019 December 31
with a Canon EOS Rebel SL2 DSLR, 24mm EF-S lens @ f/4, and an Omegon Mini Track LX2 mechanical star tracker.
The Moon brightens the early morning skies this week, coursing her way through the springtime constellations before ending the week among the rising stars of summer. Last Quarter occurs on the 4th at 12:37 pm Eastern Standard Time. Early risers will find Luna to the northeast of the bright star Spica on the morning of the 3rd. On the 6th she will be just over four degrees north of Antares, the ruddy star that marks the “heart” of Scorpius, the Scorpion.
As I write this snow is falling outside of my window, and reports from rural Pennsylvania indicate that the rodent prognosticator of all things climatic has apparently seen its shadow, thus indicating six more weeks of winter. This should not come as a big surprise to anyone since a simple glance at the calendar shows that the vernal equinox falls 45 days from today, just over six weeks away. From an astronomical point of view, boreal winter is actually our shortest season, with a duration of just under 89 days. This means that summer is our longest season with a length of just under 94 days. The reason for the shorter duration of winter is that it begins shortly before Earth reaches perihelion, its closest point to the Sun. This means that our planet is traveling at its fastest orbital speed during winter; the opposite is true in summer. In fact, the length of summer is currently slowly increasing, while winter is gradually growing shorter. This is caused by long-term variations in a number of Earth’s motions; the perihelion point drifts around the ecliptic about once in 111,000 years, while the equinoxes precess once in a bit over 25,000 years. The net effect is to slowly change the lengths of the seasons in a periodic fashion with a period of around 21,000 years. At present the extremes of summer and winter will be reached around the year 3500 CE. Spring and fall will have the same length around the year 3850. If you love winter you will have to wait awhile before it becomes the longest season. That won’t occur until sometime around the year 13,500.
The discussion above makes certain assumptions in the length of the mean solar day and the expected effects of long-term variations in Earth’s orbital eccentricity and axial tilt. Known as Milankovich Cycles, these are very long-term variations that play out over hundreds of thousands of years and are caused by perturbations of the Sun, Moon, and (primarily) the planets Jupiter and Venus. Ironically, we know more about the future effects of the Milankovich Cycles than we do about the Earth’s rotation over the long term.
While the seasons come and go, one thing that we can be certain of right now is that when you go outside at this time of year you will be greeted by the bright stars of the Great Winter Circle. These bright stars and constellations fittingly grace the long nights of winter as they have for most of recorded human history. The centerpiece of this show is the constellation of Orin, highlighted by his distinctive “belt stars” and the bright stars Betelgeuse and Rigel. Over the past few weeks we have highlighted some of the surrounding bright stars, and this week we’ll look at Aldebaran, brightest star in Taurus, the Bull. From a dark site this red-hued star seems to glimmer at the end of one tine of a V-shaped group of faint stars known as the Hyades. This group is the closest galactic star cluster to Earth, a bit over 150 light-years away. While Aldebaran appears to be a part of the cluster, it is about 85 light-years closer to us. Its ruddy tint tells us that it is an evolved “red giant” star that has exhausted the supply of fusible hydrogen in its core. Aldebaran gives us a “preview” of the fate of our Sun some 2 billion years from now.
Ruddy Mars is now the only bright planet visible in the overnight hours. Mercury, Venus, Jupiter, and Saturn are all too close to the Sun to be easily seen. The red planet is moving steadily through the faint constellation of Aries, the Ram, toward Taurus, where he will encounter Aldebaran around the time of the spring equinox.
|The Moon, Sinus Iridum and Plato region, imaged at the U.S. Naval Observatory on 2012 February 6, 23:58 UT
with the 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor, 1.6X Antares Barlow lens, and a Canon EOS Rebel T2i DSLR.
The Moon climbs higher in the evening sky this week, passing through the winter constellations as she waxes toward her full phase. First Quarter occurs on the 20th at 4:02 pm Eastern Standard Time. Look for Luna near ruddy Mars on the evenings of the 20th and 21st. On the 23rd she passes north of the bright star Aldebaran in the constellation of Taurus, the Bull.
This is another good week to do some Moon-watching. As Luna climbs higher along the ecliptic her light passes through less of Earth’s atmosphere, offering less turbulence to blur details on her surface. As she waxes into her gibbous phases two dramatically different landscapes are revealed. The two largest of her ancient impact scars contrast with the battered terrain of the “southern highlands”, where craters stand shoulder-to-shoulder as a testament to the violence of the early solar system. The two large basins known as the Mare Imbrium (Sea of Rains) and Oceanus Procellarum (Ocean of Storms) appear relatively flat compared to the pockmarked highlands. However, they were produced by collisions with large proto-planets billions of years ago. Molten rock from the lunar mantle eventually flooded these vas basins, solidifying well after the age of intense bombardment that created the highlands. The few craters that dot the surfaces of these so-called “seas” were created relatively recently on the lunar time-scale, falling within the last 3.5 billion years or so. Owners of small telescopes can delight in these features as the terminator line slowly advances across the Moon’s face.
One of my favorite features on the Moon will be well-placed for viewing on the evening of the 23rd. By this time the full extent of the Mare Imbrium will be revealed. This vast circular feature is 1250 kilometers (775 miles) in diameter and is surrounded by a series of tall mountain ranges. On its northwestern side the ring of mountains is interrupted by a semi-circular feature known as Sinus Iridum, the Bay of Rainbows. This was one of the first lunar features I identified with my first telescope, and I always like to come back to it when it is visible. Another striking feature sits along the northern edge of Mare Imbrium, the dark-floored crater Plato. This 100-kilometer (60-mile) feature is an ancient crater that was flooded with lava. Its flat surface is pocked with small craterlets; viewing these is a challenge for your telescope’s optics.
Luna’s brightening glow gradually swallows up all but the brightest of the season’s stars, but fortunately Mother Nature has seen fit to endow this part of the sky with some of the brightest of her luminaries. The brightest star in the sky, Sirius, is easily found trailing behind Orio as he gracefully wheels across the meridian. To the astronomers of the 17th Century who depicted the constellations in the first star atlases Sirius represented a gleaming jewel in the collar of Canis Major, one of Orion’s two hunting dogs. Its name is derived from the Greek word for “scorching”, and when it was observed rising just before the Sun its light was thought to amplify the Sun’s rays, causing the “dog days” of summer. Long before the Greeks the ancient Egyptians noticed that this “heliacal rise” corresponded with the annual life-giving flood of the Nile river. They saw it as the embodiment of the soul of Isis, one of their principal deities and watched for its first appearance each year for three millennia. Sirius gets its dazzle from its relative proximity to us, located a scant 8.6 light-years away. Only six star systems are closer to Earth, and only one, Alpha Centauri, can be seen with the naked eye.
You can still glimpse the elusive planet Mercury low in the southwest as evening twilight falls. The fleet planet reaches his greatest elongation east of the Sun on the evening of the 24th. You should be able to spot him by around 6:00 pm local time, when he will be a bit over five degrees above the horizon. Viewing him is a feat that, legend has it, that the great astronomer Nicholas Copernicus never achieved. Despite this detail, he correctly placed Mercury as the innermost planet in his epic work, “De Revolutionibus Orbium Coelestium”.
Mars is steadily moving eastward among the stars of Aires, the Ram. Early this week he floats just north of the more distant planet Uranus. To spot this distant “ice giant” planet look at Mars with a pair of binoculars. Uranus will appear as the brightest of the faint stars below Mars’ ruddy glow. Point a small telescope at this “star” and you will see a tiny greenish disc that’s some 2.9 billion kilometers (1.8 billion miles) away. The two planets will appear closest together from the 19th through the 22nd.
|The Moon, imaged from Alexandria, Virginia on 2020 March 2, 02:51 UT
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor and a ZWO ASI224MC color imager.
The Moon returns to the evening sky this week, with New Moon occurring on the 13th at midnight, Eastern Standard Time. On the evening of the 14th you can spot her slender crescent low in the southwest during evening twilight. Look for the elusive planet Mercury about two degrees to the right of Luna’s crescent that evening. As the week progresses the Moon climbs higher in the evening sky, drawing a bead on ruddy Mars.
The waxing crescent Moon offers fine views for owners of small telescopes. Judging from the back-ordered inventories of popular telescope vendors it looks as if many people received telescopes as gifts during the holiday season, and Luna is a great target for first-time telescope owners. I often say that the Moon is “looked over, then overlooked”, but spending time exploring her many varied surface features can be a wonderful retreat from the constant barrage of the 24-hour news cycle. As our closest neighbor in space even small instruments will show an abundance of detail, and it helps to have an atlas of the Moon handy for your exploration. There are many of these available online. The Moon’s larger features bear names that were for the most part assigned long ago by the first astronomers to gaze on her with crude telescopes. Her darker areas are known as “seas” (“maria” in Latin), “lakes” (“lacus”), “bays” (“sinus”), etc. and bear names like Mare Imbrium (Sea of Rains) and Sinus Iridum (Bay of Rainbows). These large-scale features are the remnants of collisions with large asteroids early in the history of the solar system’s formation. Individual smaller craters are named after famous people from classical astronomical literature as well as more modern contributors to lunar science. Each successive night reveals new features along the “terminator” which is the sunrise/sunset line that creeps slowly eastward from our point of view. The low Sun angle along the terminator throws features into stunning relief as ink-black shadows give way to dazzling sunlit terrain. A 3- or 4-inch aperture telescope will show many hundreds of features and terrain textures. Spend some time taking good long looks at our fair neighbor and you’ll want to return each month.
As the Moon moves farther along the ecliptic her light begins to wash out the faint stars that characterize the late autumnal constellations. To challenge her, the bright stars of winter roll into the evening hours, offering more treats for the novice telescope user. By the late evening the bright constellation of Orion, the Hunter is well up, dominating the southern sky. Surrounding him is a large circle (or hexagon) of bright stars. Point your telescope at these luminaries and you will see their colors, ranging from the icy blue of Sirius, the brightest star in the night, to the golden yellow of Capella, northernmost of the circle’s stars, to the red-tinted Aldebaran, the “eye” of Taurus, the Bull, and Betelgeuse, the left-hand “shoulder” of the Hunter himself. Now sight in on Castor, the fainter of the two Gemini “twin stars” to the northeast of Orion. Your telescope will reveal two stars tucked close together. Each of these stars is itself a binary star, as is a fainter companion nearby, thus making Castor a six-star system!
As mentioned earlier, the planet Mercury is now putting in an appearance in the evening twilight sky. Mercury never strays very far from the Sun, so he’s almost never visible against a dark sky. This week, though, he advances eastward from the Sun’s glare for one of his better evening apparitions for the year. The Moon will help you find him at dusk on the 14th, and each night for the next week or so you should look in the same general part of the sky for his glow.
Mars continues his eastward trek through the late autumn stars. He is still easy to spot despite his fading light. He is now some 10 times fainter than he was at opposition, but his red hue and lack of nearby bright stars should make him easy to pick out. Through the telescope you’ll see a tiny gibbous pink disc.
Venus is now becoming a challenge to early-rising skywatchers. She now rises in gathering twilight an hour before the Sun. You will need a flat eastern horizon to catch her before she is overwhelmed by the pending sunrise.
|The Full Cold Moon (and Orion) rising, Ocean City, Maryland, 2020 December 29
HDR image made with a Canon EOS Rebel SL2 DSLR and EF-S 18-55mm zoom lens @ 18mm, f/8.
The new year finds the Moon waning in the morning sky, coursing her way through the rising constellations of spring. Last Quarter occurs on the 6th at 4:37 am Eastern Standard Time. You’ll find Luna to the northwest of the bright star Spica before dawn on the 6th. By the week’s end she is low in the southeastern sky, passing through the first of the rising summer constellations.
Earth reached perihelion, its closest point to the Sun, on January 2nd. Fortunately for us our planet’s yearly excursion around our star follows a nearly circular path that varies only 5 million kilometers (3 million miles) between apsides. The eccentricity of Earth’s orbit varies over periods of hundreds of thousands of years due to the gravitational influence of the other planets in the solar system. Currently it is trending toward a more circular state, reaching a minimum in about 28,000 years.
We are now at the point in the year where we are seeing the latest sunrises in the Northern Hemisphere. Here in Washington Old Sol crests the horizon at 7:27 am EST. By the end of the week he will rise one minute earlier. However, the time of sunset is now just after 5:00 pm and we have added five minutes of total daylight since the winter solstice. The longest nights of the year are now safely in the rear-view mirror.
The splendor of our winter constellations is best appreciated during the month of January. The stars that comprise the “Great Winter Circle” dominate the evening hours, led by the striding figure of Orion, the Hunter. No other constellation boasts as many bright and colorful stars as this one which is visible from every inhabited part of the globe. Anyone who has done any casual stargazing on a winter night has probably noticed the three perfectly aligned stars that make up Orion’s “Belt” framed by the first-magnitude stars Betelgeuse to the northeast and Rigel to the southwest. All of these stars are easily visible from urban environments, but it is the view from more rural sites that really brings out the splendor of the constellation. From a dark site the first thing you will notice are the colors of the principal stars. Betelgeuse shines with a ruddy tinge while Rigel and the Belt Stars sport an icy blue hue. These colors tell us something about the nature of these stars. Betelgeuse is relatively cool while its companions are very hot. All of these stars shine across enormous gulfs of space, ranging from about 550 light-years for Betelgeuse to 2000 light-years for Alnilam, the middle star in the “Belt”. The latter is one of the most intrinsically bright stars in our galaxy, with some 500,000 times the luminosity of our little Sun.
As midnight falls another brilliant blue star lies on the meridian at the end of a southeasterly line from Orion’s belt. This is Sirius, the brightest star in the entire sky and chief luminary of Canis Major, the Greater Dog. Unlike Orion’s powerhouses, Sirius is bright by dint of its proximity, just 8.6 light-years away and a luminosity of 25 Suns. Both Sirius and Orion figure prominently in the sky lore of many ancient civilizations and led to humanity’s first reckonings of time.
Another planetary gathering takes place in the southeastern sky at dusk this week when Mercury, Jupiter, and Saturn convene in the early twilight. From the 9th to the 11th the three planets will be within three degrees of each other, but they will only be a few degrees above the horizon at 5:30 pm local time. You will need a very clear sky, an unobstructed horizon, and binoculars to easily see them.
Mars is now the sole planet that’s easily visible during the evening hours. You will find his ruddy glow on the meridian at 7:00 pm as he makes his way from the bounds of Pisces into the diminutive constellation of Aires, the Ram. Mars appears slightly brighter than Betelgeuse in Orion, but the two objects share a warm reddish tint. Mars now shows a small gibbous-phase disc in the telescope eyepiece.
You can still spot bright Venus low in the southeast half an hour before sunrise. Look for a very slender crescent Moon near her before dawn on the 11th.
|Great Conjunction + 1 day, imaged at the U.S. Naval Observatory, 2020 December 22
with a Canon EOS Rebel SL2 DSLR and USNO's 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor.
‘Tis the Night Before Christmas and up in the dome
We eagerly wait for the nightfall to come.
The slit has been opened, the lens cap’s been stowed
The night sky awaits like a wide-open road.
The solstice just passed on the 21st day,
The Sun’s southernmost point on his orbital way.
The year’s longest nights are upon us right now
But they start to get longer when the Yule log’s aglow.
The Moon is now waxing through autumnal stars
Her gibbous begins the week passing by Mars.
Full Moon occurs on the 29th hence,
Then wanes among spring’s stars as the New Year commences.
Jupiter shines in eve twilight’s last glow,
With much fainter Saturn behind him in tow.
The pair were quite close when the solstice occurred,
Old Jove moving eastward will get the last word.
Red Mars dashes quickly through Pisces’ faint lights,
His ruddy glow fading as he recedes in the night.
He’ll be with us well into summer next year,
By August he finally will disappear.
The Great Winter Circle shines high in the night
With bright stars a-twinkling with all of their might.
Their colors add contrast to enhance the dark sky
While far down below they’re a treat for the eye.
Orion is now rising high up in the east,
Shield raised in defiance of Taurus the beast.
The Great Winter Circle surrounds his bold shape,
While faithful dog Canis leaps up in his wake.
Late night brings Sirius, the Dog Star on high,
By New Year’s he transits as midnight draws nigh.
The brightest of stars warm the long winter’s night,
His colorful cohorts all add to the sight.
Ten of the brightest of stars in the sky,
Light these long nights of winter as Old Sol plays shy.
With the solstice now past us we’ll all soon be glad,
For the days getting longer than the ones we’ve just had.
The first stars of summer rise just before dawn
With dazzling Venus soon tagging along.
The planet’s bright glimmer shines in the southeast
As brightening twilight snuffs the bright stars to sleep.
So Peace to your families, neighbors, and friends,
We wish you the best that the holiday sends.
The stars mark the comings and goings of time,
So stop to enjoy them, and so ends my rhyme.
Happy Holidays from all of us at the U.S. Naval Observatory!
And my most sincere apologies to Clement Clark Moore.
|Orion (with faded Betelgeuse), imaged 2020 January 1 from Mollusk, Virginia
captured with a Canon EOS Rebel SL2 DSLR on an Omegon MiniTrack LX2 mechanical star tracker
The Moon returns to the evening sky this week, waxing to First Quarter on the 21st at 6:41 pm Eastern Standard Time. Look for Luna’s slender crescent low in the southwest near the close pairing of Jupiter and Saturn in the twilight hours of the 16th and 17th. By the end of the week you will find her approaching ruddy Mars.
The 21st also marks the date of the winter solstice, which will occur at 5:02 am EST. This is the moment when the center of the Sun’s disc reaches an ecliptic longitude of 270 degrees relative to the center of the Earth. In more practical terms it is also the day when the Sun reaches its most southerly point along the ecliptic, providing Northern Hemisphere residents with the shortest day of the year. Here in Washington, DC that corresponds to 9 hours 26 minutes of daylight. At the time of the solstice Old Sol will be directly overhead about 250 kilometers (150 miles) north of Pretoria, South Africa.
Yet another event occurs on the 21st this year in the form of a sight last seen by people in the year 1226 CE. This will be the extraordinarily close pairing of the planets Jupiter and Saturn that will play out in the evening twilight sky. If you’ve been watching the two planets over the course of the past few months you have seen Jupiter slowly but surely inch up on Saturn, and on the 21st they will pass just six arcminutes apart from each other. While they won’t appear to merge together as seen with the unaided eye, that apparent distance is about one-fifth the apparent diameter of the Moon. They will produce a spectacular view in the low-power field of a telescope, especially as the sky darkens and their respective flocks of moons become visible. These two planets generally encounter each other about every 19.8 years, and when they meet it is often called a “Great Conjunction”. After 19 of these encounters, their 20th can be very close, as is the case here. They were actually a tad closer in 1623, but that conjunction took place on the far side of the Sun and so was not visible. The 1226 close conjunction, which occurred on March 5th, brought the two planets to within three arcminutes of each other in a dark sky, which must have caused great consternation to astrologers of the day. The next close encounter of the two gas giants will occur after 19 more Great Conjunctions. On August 24, 2417 they will once again pass very close to each other, just five arcminutes apart. Mark your calendars!
The long winter nights may be dark, but Mother Nature has seen fit to do her part to brighten the view. By the late evening the spectacular constellations of the Great Winter Circle are marching toward the meridian, led by perhaps the most splendid of all, Orion, the Hunter. Within the bounds of the circle you will find ten of the 30 brightest stars in the sky, four of which reside in Orion. You may recall that last year one of Orion’s stars lost much of its luster; Betelgeuse, the red-tinged star marking one of the Hunter’s shoulders, faded to about the same brightness as the three “Belt Stars”. Happily the star has returned to its former brightness this year, but astronomers are still baffled by its deep minimum.
A somewhat brighter red-hued object now dominates the early evening hours. Mars crosses the meridian at around 7:30 pm local time, set like a glowing coal among the faint stars of Pisces. Although he has lost much of the luster he had at opposition in early October, he still has the ability to get your attention. The distance between Earth and Mars is rapidly increasing now, and his apparent disc is now just half the size that it was back then. You will need at least a six-inch telescope to see details on his distant surface.
Venus is gradually dropping toward the Sun in morning twilight. She rises at around 5:30 am, just before the onset of morning twilight. Look for her bright glow in the southeastern sky about half an hour before sunrise.
|The Milky Way in Perseus and Cassiopeia, imaged 2019 September 28
from Blackwater Falls State Park, Davis, West Virginia
captured with a Canon EOS Rebel SL2 DSLR
The Moon wanes in the morning skies this week, moving southward along the ecliptic as she passes through spring’s rising constellations. New Moon occurs on the 14th at 11:17 am Eastern Standard Time. Those who happen to be located in southern Chile and Argentina will be treated to a total solar eclipse at that time. For 2 minutes and 10 seconds the Sun’s face will be completely obscured by the Moon in one of Nature’s most spectacular sights. Can’t get to Patagonia by next week? Not a major problem. You’ll only need to wait until April 8th, 2024 for a 4.5-minute eclipse that crosses the U.S. from Texas to the Great Lakes and northern New England.
Another of Nature’s spectacles is gearing up for a splendid viewing opportunity over the weekend. The annual Geminid meteor shower will peak on the night of December 13-14, and there will be no moonlight to interfere with the view. This is one of the most consistent showers from year to year, with up to 100 meteors visible per hour from dark locations. The shower members appear to radiate from a point in the sky near the bright star Castor in the constellation of Gemini, and unlike many meteor showers the radiant is well above the horizon in the evening hours. By 10:00 pm local time the radiant is about 40 degrees above the horizon, and it is almost directly overhead at 2:00 am. Geminids are characterized by relatively slow, bright meteors that can be vividly colored. Unlike summer’s Perseids, these slower meteors don’t tend to leave persistent smoke trains behind them. While almost all of the year’s periodic showers are produced by the passage of comets through the inner solar system, the Geminids are the spawn of an asteroid, (3200) Phaethon. Discovered in 1983, this was the first asteroid to be found by a space-based instrument, and it has the distinction of having the closest perihelion distance of any named asteroid. It is now thought to be a defunct comet nucleus, sputtering off material as it orbits the Sun every 1.43 years.
This is the final week in 2020 to participate in the Globe at Night citizen-science sky awareness program. From now until December 15th you are encouraged to go outside, look up, and count stars. This month’s featured constellation is Perseus, the Hero, which may be found high in the northeastern sky in the mid-evening hours. Perseus lies just west of a line that connects the bright yellow-hued star Capella with the W-shaped asterism formed by Cassiopeia. Look for a grouping of stars that resemble a wish-bone with the bright star Mirfak at the intersection of the wish-bone’s tines. To make an observation, simply visit the web app on the Globe at Night website and compare your view of Perseus with the charts on the site. The site’s sponsors are hoping to collect a total of 30,000 observer reports for the year.
The second-brightest star in Perseus is usually Algol, which is normally a second-magnitude object. However, every 2.8 days the star fades to magnitude 3.4. It is the prototype of a class of variable stars known as eclipsing binaries in which a brighter star is periodically eclipsed by a darker companion. Its variability was first documented by Medieval Persian astronomers who named it “Al Ra’s al Ghul”, the Demon’s Head. The demon it represented was the Gorgon Medusa in Greek mythology, a creature who had snakes for hair and the ability to turn people to stone if they looked into her eyes. The clever Perseus was able to kill Medusa by looking at her reflection in his polished bronze shield before lopping off her head, which the Hero subsequently carried around with him as a grisly trophy. This week Algol reaches one of its minima on the evening of the 8th at 9:38 pm EST. Five hours later it will have regained its regular brightness.
Bright Jupiter continues to inch up on Saturn during evening twilight into the first hour of darkness. You can easily spot Jupiter in the southwest shortly after sunset, and Saturn should appear shortly thereafter. Jupiter will pass Saturn in two weeks in what is often called a “Great Conjunction” since it only occurs every 19.76 years. This particular one will be truly memorable as the two objects will appear extremely close together on the evening of the 21st. The last time they appeared this close together and were easily visible was the year 1226 CE!
Mars continues to shine through the night, but his brightness is gradually fading. Fortunately he is located in a part of the sky that is bereft of bright stars, so he stands out despite his waning glory. You can also identify him by his strong ruddy tint, unmatched by any other object in the sky. If you have been following him through the telescope since his close opposition two months ago you will see that his disc is now almost half as big as it appeared at that time.
Bright Venus can be spotted in the gathering morning twilight as she moves through the stars of the constellation of Libra. She gets a visit from the waning crescent Moon on the mornings of the 12th and 13th.
|The Full Beaver Moon and Halo, imaged 2020 November 29 from Alexandria, Virginia
HDR image captured with a Canon EOS Rebel SL2 DSLR
The Moon begins the week high above the rising stars of the Great Winter Circle, then wends her way into the morning sky as she wanes to Last Quarter, which will occur on the 7th at 7:37 pm Eastern Standard Time. By the end of the week pre-dawn skywatchers can see her among the rising stars of the springtime constellations.
December 1st is generally considered to be the start of climatological winter, and all month long the Sun plays out a series of extremes centered on the winter solstice. From now until December 11th we will experience the earliest sunsets of the year. Here in the Washington, DC area that means that Old Sol slips below the horizon at 4:46 pm EST. After the 11th he will gradually begin to set a tad later each day, and by Christmas he’ll set at 4:52 pm. However, the time of sunrise is still creeping later each morning and won’t reach its latest time until the year’s end. Fromm December 30th until January 10th sunrise in DC will be at 7:27 am. The dates of these extremes are bisected by the solstice itself, which falls on the 21st. This will be the shortest day of the year in the Northern Hemisphere. In Washington we will see only 9 hours 36 minutes of daylight on that date.
This seemingly lopsided swing in the dates of solstice phenomena is a reflection on our desire to keep precise time. If you were to measure time with a sundial, the dates of latest sunrise and earliest sunset would correspond to the solstice. For centuries this scheme was adequate, but as mechanical timepieces became more precise it became apparent that the time kept by the Sun varied in its uniformity throughout the year. Since the Earth travels on an elliptical orbit around Old Sol its orbital velocity changes, moving faster at perihelion and slower at aphelion. However, its speed of rotation remains essentially constant throughout the year. The time of “noon” as measured by a sundial occurs when the Sun crosses the sundial’s meridian, so as far as the sundial is concerned noon is always 12 o’clock. However, bring a clock of constant rate into the mix and you’ll discover that the apparent time of the Sun’s noon meridian transit is not precisely every 24 hours. Depending on the time of year the apparent noon transit of the Sun can be as much as 16 minutes ahead of or 14 minutes behind “clock time”, and the most rapid excursion between these points happens to occur between early November and mid-February, skewing the “clock times” of latest sunrise and earliest sunset. A similar effect occurs around the time if the summer solstice, but its amplitude is about half of what it is in the winter. The annual variation between apparent solar (i.e. sundial) time and clock time is known as the “equation of time”, and its graphical solution may be found in the form of the “figure 8” diagram that’s usually printed on Earth globes and maps in the middle of the Pacific Ocean. This figure is called the “analemma”, and provides you with a handy guide to correct your sundial to the proper clock time…at least for a while. The Earth is gradually slowing in its rotation, and the eccentricity of its orbit and its axial tilt are slowly changing as well. Eventually we’ll have to redraw the analemmas on our globes.
Early evening skywatchers can still catch Jupiter and Saturn in the southeastern sky as evening twilight settles over the landscape. Both planets are gradually losing ground to the Sun, setting about three minutes earlier each passing night. Jupiter has a slight advantage, though, as you can see by watching him inch closer to Saturn over the next few weeks
Mars is now the planet that will get your attention each night. He crosses the meridian shortly after 8:00 pm local time, and his pink tint distinguishes him from all other bright objects in the sky. He continues to fade gradually as the distance between him and Earth increases, and the telescope will show that his disc is shrinking rapidly as well. Details on his distant surface are becoming harder to see as he recedes from us, and the recent development of one of his infamous dust storms further hinders the view.
You can still find bright Venus in the pre-dawn sky, but she, too, is gradually inching closer to the glare of the Sun. Look for her in the southeastern sky in the gathering morning twilight.
|Messier 45, The Pleiades, imaged 2017 December 17 from Great Meadow, Virginia
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor and a Canon EOS Rebel T2i DSLR
"Many a night I saw the Pleiads, rising thro' the mellow shade,
The Moon returns to the evening skies this week, waxing through her crescent phases as she climbs through the faint autumnal constellations. First Quarter falls on the 21st at 11:45 pm Eastern Standard Time. Luna starts the week near Jupiter and Saturn, appearing closest to the pair of planets on the evening of the 19th. By the week’s end she will approach the ruddy glimmer of Mars.
If you have an unobstructed view of the northern horizon, this is the time of year when the familiar asterism known as the Big Dipper reaches its lowest point in the sky, scraping the tree-line in its endless journey around Polaris, the North Star. The seven stars of the Dipper are the brightest members of the larger constellation of Ursa Major, the Great Bear. Our present association of a bear with these stars has a long tradition dating back at least to classical Greek times, and it may possibly date back even further to folklore that developed in prehistory. Many cultures in the Northern Hemisphere identify it as a bear, including many Native American peoples. One of my favorite stories comes from the Iroquois people who inhabited much of the northeastern U.S. before Europeans arrived. They saw the four stars of the “bowl” of the Big Dipper as a bear, while the three stars of the “handle” represented three hunters. The hunter closest to the bear carried a bow and arrows, while the hunter at the end of the “handle” carried firewood. The star we now call Mizar, which forms the bend in the “handle”, was a hunter who carried a pot, represented by the naked-eye companion to Mizar, the star Alcor. Every year the hunters pursued the bear around the pole, and each autumn, as the bear neared the northern horizon, they caught it and cooked it in the pot. The blood from the bear’s arrow wounds dripped down to Earth, staining the trees red and causing the leaves to fall. The hunters, in turn, had a well-stocked larder for the coming winter.
Later in the evening, if you look to the east, you will find another star pattern associated with boreal winter. While it is a very diminutive group that can barely be seen from the city, it stands out in the sky as you move to darker skies. This group is the Pleiades, also known as the Seven Sisters in our Greco-Roman derived sky lore. Ancient Chinese records dating to some 4500 years ago mention them, and recent work by archaeoastronomers has shown that many Mesoamerican cultures built their ceremonial centers to align with the Pleiades’ rising. Virtually every culture that has left some record of their sky legends mentions the group, and they even appear in the lore of the fabled Middle Earth of J.R.R. Tolkien’s epic tales of hobbits, elves, and magic rings, where they were known as “Remmirath”, the “Netted Stars”. In Japanese they are known as “Subaru”, and you can see a stylized representation of them on every car of that name. They are often associated with the coming of winter in northern climes, and sailors regarded them as portents of gales and fierce seas. Others associate them with agriculture, marking the time to plant when they set just after the Sun in the spring and time to reap when they appear in the fall.
The Pleiades are a true star cluster, located about 440 light-years from Earth. Its brightest members have a dazzling blue tint as seen in a telescope and under very dark conditions it is possible to see the remnants of the clouds that formed them some 100 million years ago. Most of us can see six or seven stars with the unaided eye, but very keen-eyed people can see a dozen. A small telescope will reveal about 80 members, while large telescopes have identified over 1000 stars in the cluster.
Jupiter and Saturn may still be glimpsed in the southwest as evening twilight fades to darkness. They will get a visit from the Moon on the evenings of the 18th and 19th. If you have been watching them for the past few weeks you’ve probably noticed that the gap between them is narrowing; Jupiter is gradually gaining ground on the ringed planet. The gap will continue to close, and in a month we will see the closest appulse of these two planets since the year 1623.
Mars has resumed his eastward motion against the stars, but it will be a few more weeks before this becomes noticeable. He still dominates the sky throughout the evening hours beaming down from among the faint stars of Pisces. Although his disc is now shrinking, a modest telescope on a night of steady seeing will reveal his dusky surface features and small polar ice cap.
You will find Venus in the pre-dawn sky without much difficulty. Her bright glow remains visible right up to the time of sunrise. If you look for her at around 5:30 am you should see her near the bright star Spica as the week begins. She moves rapidly east from the star over the next several mornings.
|Messier 31, the Andromeda Galaxy, imaged 2018 October 7 from Mollusk, Virginia
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor and a Canon EOS Rebel T2i DSLR
The Moon may be found in her waning crescent phases before dawn as the week opens. New Moon occurs on the 15th at 12:07 am Eastern Standard Time. Look for Luna’s crescent about six degrees above dazzling Venus in the morning twilight of the 12th. On the following morning the Moon is about halfway between Venus and her inner solar system companion Mercury.
Crisp late autumn nights with no Moon in the sky mean that it’s time for the November observing campaign for the citizen-science program Globe at Night. This month’s target constellation is Pegasus, the mythical Flying Horse. Its “landmark” feature is an almost perfect square made up of second-magnitude stars that transits the meridian at around 8:30 pm. Pegasus is high in the sky for mid-northern observers, and I have always used it as a test for dark skies. Within the square are a number of faint stars to help you judge the quality of your sky. Urban and near-suburban skywatchers probably won’t see any stars within the bounds of the square, but as you venture further out into the country faint stars begin to fill it in. If you can spot three or four stars in the square you are in a pretty dark locale, but observers in truly dark sites can spot nearly a dozen! You can contribute your star count with the Globe at Night Web App, which gives you a very simple interface to report your findings. So far this year the program has gathered over 26,000 reports, and the program’s goal is 28,000 by the end of the year. The program aims to chart light pollution and its effects on both professional and amateur astronomers.
If you are in a place where you can see some of the faint stars in the square take a few moments to track down something that’s almost mind-boggling. The upper left corner of the square is marked by the star Alpheratz, which is shared by Pegasus and the constellation of Andromeda. If you allow your gaze to wander toward the “W” of Cassiopeia you will notice two diverging “chains” of stars that lead from Alpheratz. Follow the lower, brighter chain to the second star, then draw an imaginary line to the second star in the upper, fainter chain. Extend your gaze in the same direction for the same distance and you will notice a fuzzy patch of light that looks like a tiny detached portion of the Milky Way. It is, in fact, another galaxy like our own, its faint light glimmering across 2.5 million light-years of intergalactic space. Known as the Andromeda Galaxy, this is the most distant object that you can see with the unaided eye. Its elongated shape becomes apparent in binoculars, and it stubbornly refuses to resolve into stars in virtually any amateur telescope. Its light was described very aptly by the German astronomer Simon Marius in 1612 who remarked that it resembled “the light of a candle shining through horn”. That light is the combined light of several hundred billion stars!
The Andromeda Galaxy and the Milky Way are the two largest members of the “Local Group” of galaxies, a loose grouping of a few dozen small systems under the sway of that larger ones. The Andromeda Galaxy is moving toward us, and the mutual gravity of the two systems will bring them together in a slow-motion collision in about 4.5 billion years.
Back in our solar system, Jupiter and Saturn are struggling to stay ahead of the relentless Sun. The two giant planets are still easy to spot in the southwest after sunset, but by the time that twilight ends they are dipping toward the horizon. Jupiter will ultimately win the race, passing Saturn in a spectacular conjunction on the winter solstice.
Mars holds court in the evening sky, especially as Jupiter sinks into the trees. The red planet is very hard to miss. Not only is he bright, he sports a decidedly ruddy tint and has no competition from nearby bright objects. However, his diminutive size means that as we earthlings recede from him he gets a bit fainter each passing night. His apparent diameter is quickly shrinking as well. That said, his disc won’t approach this size again until the year 2033.
Venus continues to gradually inch toward the Sun in the pre-dawn sky. She is still easy to see over the eastern horizon as twilight begins to gather. The Moon will be in her vicinity on the mornings of the 12th and 13th.
Elusive Mercury also puts in an appearance just before sunrise. He reaches greatest elongation from the Sun on the 10th, and you should be able to spot him about 10 degrees below Venus. The best time to look for him will be the morning of the 13th, when the Moon is halfway between the two planets.
|The Perseus Double Cluster, imaged 2018 October 7 from Mollusk, Virginia
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor and a Canon EOS Rebel T2i DSLR
The first full week back on Standard Time finds the Moon cruising high on the ecliptic as she wends her way through the rising stars of the winter constellations. Last Quarter occurs on the 8th at 8:46 am Eastern Standard Time. Luna begins the week between the “horns” of Taurus, the Bull, then passes through the constellation of Gemini, the twins and the obscure stars of Cancer the Crab. Early risers will find the Moon passing through the “head” of Leo, the Lion, mid-way between the bright star Regulus and the gold-hued glimmer of Algieba.
“Falling back” to Standard Time is usually a bit of a shock for me. I enjoy being out under the stars, but usually not until after dinner. Now the sky is dark when I sit down for my evening meal, and when I do head out with my telescope it’s as if an entire season has suddenly elapsed. The three stars of the Summer Triangle, Vega, Deneb, and Altair, along with their attendant constellations, are now poised to set, leaving the barren autumn stars patterns to occupy the sky over my yard. That said, I don’t have to wait too long before the bright stars of winter begin to rise. One of my favorite sights is the figure of Orion seeming to climb over the horizon, ready to ward off the charge of nearby Taurus.
High overhead is the diminutive W-shaped group of stars that form Cassiopeia. This area of the sky is rife with an array of beautiful star clusters that glitter like tiny jewel boxes in the telescope eyepiece. From a dark site you can see a fairly bright portion of the Milky Way behind the constellation’s main stars that trails off into the neighboring constellation Perseus. This constellation has a shape that reminds me of the “winner’s portion” of a wishbone, with the bright star Mirfak at the wishbone’s center. Embedded in the Milky Way between Perseus and Cassiopeia is one of the true treasures of the sky, the “Double Cluster”.
From a dark sky the Double Cluster appears as a fuzzy patch of light to the naked eye, but a pair of binoculars will begin to resolve its starry splendor. My favorite view is through my 4-inch telescope at low magnification where the two star clusters can be seen in the context of the Milky Way background. Each cluster resolves into hundreds of stars, and at a distance of some 7500 light years, the brighter members must be enormously luminous to appear as they do in the eyepiece. Most of the bright stars are blue supergiants, which means that the clusters are quite young on the cosmic scale, forming just 10 to 15 million years ago. Careful scrutiny will also show a smattering of red supergiant stars scattered between the two main clusters. These stars are analogous to Betelgeuse in Orion, but they are over five times farther away.
Shifting our gaze back to Perseus, another much closer star cluster surrounds the constellation’s brightest star, Mirfak. This group, known as Melotte 20, is widely scattered and is best seen in binoculars. It is about 510 light-years away. Ten of its members are visible to the naked eye, but binoculars will reveal dozens more. Most of the stars, apart from Mirfak itself, have a pleasing blue tint.
Returning to Standard Time places Jupiter and Saturn into the early evening sky, and if you wait too long they will be gone for you. Jupiter sets at around 9:30 pm with Saturn following a bit over 20 minutes later. Your best views are still in evening twilight, so plan on a late dinner if you still want to see them at their best.
Mars actually benefits from the return to Standard Time. The red planet crosses the meridian at around 10:00 pm, so you have the best part of the night to give him a look through the telescope. Keen-eyed observers will note that he is already beginning to fade after his close opposition a few weeks ago, but his disc can still reveal tantalizing features to patient observers. I enjoy looking at Mars since it is the only place in the solar system other than the Moon and Mercury where I’m looking at a solid surface.
Venus remains visible before sunrise, glowing brightly among the stars of Virgo. On the morning of the 5th she passes one degree south of the beautiful second-magnitude double star Porrima. Closer to the horizon look for the first-magnitude star Spica. Early in the week the glimmer of elusive Mercury may be seen a few degrees east of the star.
|Sagittarius and the summer Milky Way
imaged from Smith's Ferry, Idaho, 2017 August 21
The Moon skims the southern horizon this week, waxing toward her Full phase, which occurs on September 2nd at 1:22 am Eastern Daylight Time. We usually call September’s Full Moon the Harvest Moon, but I have always thought that this name was best used on the Full Moon that occurs closest to the autumnal equinox. That Full Moon will fall on October 1st, a time when farmers would be traditionally bringing in their harvested bounty. Fortunately, some crops are at their peak ripeness now, so an early September Full Moon is often called the Corn Moon, Barley Moon, or Fruit Moon. Luna passes just south of bright Jupiter on the evening of the 28th. On the following night she will be just southeast of Saturn.
We are now approaching the time of year when we see the greatest rate of loss in the length of daylight. Over the course of the week we will lose about 17 minutes of total daylight, with 10 minutes of that coming off our sunset times. Since the time of the summer solstice more than an hour and a half of daylight has disappeared, and we’ll lose another hour by the time the equinox occurs.
The lengthening nights have a positive side, though, since we can now enjoy stargazing at more reasonable times. The constant seasonal change of the constellations seems to slow a bit during the late summer and early autumn, giving us more time to take in the splendors of the summer sky. Even with the brightening Moon moving through the evening sky we can still see the brighter summer constellations. To the south, the curving arc of the stars of Scorpius hover over the southern horizon, led by the orange-tinted star Antares. You will find three second-magnitude blue-tinted stars that mark the Scorpion’s “head” to the right of Antares. The middle star of this trio is called Dschubba, and over the past few years it has shown remarkable variability. Normally it is comparable to its northern and southern companions, but a couple of times over the past 20 years it has doubled in brightness, second only to Antares as the constellation’s brightest star. North of Dschubba is the star Acrab, which resolves into a fine double star in small telescopes. However, there is more than meets the eye here, as each component is itself a triple-star system. I often wonder what it might be like to live on a planet in orbit around such unusual star systems!
East of Scorpius is the constellation of Sagittarius, the Archer. To the ancients this represented a Centaur, a mythical beast with the head and torso of a man and the body of a horse. Here is one of those situations where I have trouble “seeing” what the ancients saw, but fortunately we can look at the constellation’s brighter stars and delineate a fairly respectable “teapot” asterism. If you have a really clear view of the southern horizon you can even imagine tea being poured out of the teapot’s spout into the tail of Scorpius, which makes an acceptable tea mug! On moonless nights look for “steam” emanating from the teapot’s spout; that’s the bright Sagittarius star cloud of the Milky Way. Our Galaxy’s center is about 30,000 light-years off in that direction.
The bright planets Jupiter and Saturn follow Sagittarius across the southern sky. Jupiter’s retrograde motion has brought the giant planet closer to the “handle” of the teapot, and if you look at Old Jove with a pair of binoculars you will find him under another asterism known as the “teaspoon”. Jupiter now crosses the meridian at 10:00 pm local time, so he’s in prime viewing position during the evening hours. Look for the planet’s famous Great Red Spot near the center of his disc on the evening of the 29th. On the following night you can watch his innermost large moon Io transit his disc with its shadow following behind it.
Saturn is also in prime viewing position during the evening hours. Detail on this planet is much more subtle than the prominent cloud belts of Jupiter, but that is more than made up for by the planet’s enigmatic ring system. Thanks to the multi-year observations of the Cassini space probe we now know that the rings are composed of a myriad of chunks of ice that form the flattest structure known in the solar system. While they span hundreds of thousands of kilometers in diameter, they are less than 100 meters thick!
Mars continues to drift through the faint stars of Pisces and is still best placed for viewing in the wee hours of the morning. He’s slowing his eastward pace as Earth catches up to him, and he will begin retrograde motion in another two weeks. He is well within range of modest amateur telescopes, so if you’re up before dawn consider giving him a look.
Venus joins the rising stars of winter, beaming down from a northeasterly perch as morning twilight begins. This week you will find her plodding eastward between the stars Castor and Pollux in Gemini and the star Procyon in Canis Minor.
|Scorpius and the summer Milky Wa7
imaged from Mollusk, Virginia, 2020 July 26
The Moon returns to the evening sky this week, waxing through her crescent phases to First Quarter, which occurs on the 25th at 1:58 pm Eastern Daylight Time. As she dives southward along the ecliptic, you will find her just over five degrees north of the bright star Spica on the evening of the 22nd. She ends the week among the stars that form the “head” of Scorpius, the Scorpion.
For those of you who like stargazing in the evening sky, you may have noticed that sunset here in the Washington area now occurs before 8:00 pm. That’s about 40 minutes earlier than the time of sunset at the summer solstice. This means that for many of us in urban and suburban locations we can enjoy dark (ish) skies at around 9:00 pm. If you’re in a darker location the sky is fully dark by around 9:30 pm. We are currently losing about 2.5 minutes of daylight per day, so it’s becoming easier to enjoy your summer favorites and still get to bed at a decent hour.
Speaking of Scorpius, you will find this signature summer constellation crossing the meridian at 9:00 pm local time. While it is placed in the southernmost reaches of our Washington skyline it is still one of the showpieces of the sky. If you can find a spot to see it in all of its splendor you won’t need a lot of imagination to understand how it got its name. Scorpius is a very ancient constellation, depicted in records of ancient Egypt and Mesopotamia that date back well over 5000 years. It is led by a prominent red-hued star known as Antares, which translates as “rival of Mars”. Antares is a red supergiant star, a highly evolved example of a star that is nearing the final stages of its life. Like its counterpart Betelgeuse in Orion, Antares is vast, with a girth that spans hundreds of millions of kilometers. If Antares occupied our Sun’s place in the solar system, the orbit of Mars would be inside of it! Scorpius shares some other details with Orion as well. Many of its stars are hot blue giant stars that share a common origin, much like the bright blue stars in Orion. While the two constellations share similar physical characteristics, their mythology is also linked, but in an unusual way: you will never see the two in the sky together at the same time.
Our Greco-Roman skylore tradition paints Orion as a boastful hunter who claimed that he could kill all the animals on Earth. His pride and arrogance didn’t sit well with Gaia, goddess of the Earth, so she sent a scorpion to teach the hunter a lesson. The scorpion’s powerful sting dispatched Orion, but he was saved “in the nick of time” by Ophiuchus, the Serpent-bearer, whose large constellation appears above Scorpius in our summer sky. To appease both parties Zeus placed both Orion and the scorpion in the sky, but opposite each other so that they would never have to face off again.
Early in the week you can still see the bright stars-clouds of the Milky Way from dark-sky locations. They rise up from the vicinity of Scorpius and arc overhead through the bright stars of the Summer Triangle. Mild summer evenings make them particularly attractive to scan with binoculars or small telescopes. The sheer number of stars that you can see is mind-boggling. Also note the dark, seemingly empty regions of the Milky Way’s band. These are clouds of non-luminous gas and dust that feed the formation of stars along the Galaxy’s plane.
Jupiter now shines brightly in the southeastern sky as soon as evening twilight starts to fall. Old Jove is now in prime viewing position for evening stargazers, offering a variety of sights for the small telescope owner. His constantly shifting bright moons and changing atmosphere can be studied with telescopes of four-inch aperture or larger. On the evening of the 23rd you can watch his innermost moon Io drag its shadow across the planet’s disc, and on the following evening you can get a fine glimpse of the famous Great Red Spot rotating across his face.
Saturn should be your next stop after Jupiter. I have been looking at this planet for decades through dozens of different telescopes and I still get a chill when I view it. There is something about the view of Saturn that defines “other-worldly” and keeps me at the eyepiece. One glimpse for yourself and I think you’ll see why.
Ruddy Mars waits in the wings, now rising at around 10:30 pm. That’s still a bit late for me, but with later times of sunrise it’s now not unreasonable to take a look at the red planet in morning twilight. He is steadily brightening and his visible disc is steadily growing as we near opposition, set for early October.
Venus accompanies Orion and the other rising winter constellations as morning twilight brightens the sky. You should have no trouble spotting her beaming down from the stars of Gemini.
|Jupiter & Saturn, imaged from the U.S. Naval Observatory, Washington, DC, 2020 August 11
with the 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor.
The Moon wanes in the pre-dawn sky this week, making her way through the rising winter constellations as the first light of dawn begins to brighten the eastern horizon. New Moon occurs on the 18th at 10:42 pm Eastern Daylight Time. You will find Luna just north of the bright star Aldebaran in Taurus, the Bull, on the morning of the 13th. Luna will be close to dazzling Venus before dawn on the 15th.
As we mentioned last week, the annual Perseids meteor shower peaks on the nights of the 11th-12th and 12th-13th. However, these aren’t the only nights to see members of this famous shower. Activity from the Perseids will continue through the end of the month, and the shower will maintain about a quarter of its peak strength until late in the week. Moonlight becomes less of a factor as the week passes, so if conditions aren’t great for viewing on the peak nights you can still see a decent show for a while longer.
The absence of the Moon means that it is time for the August campaign for the Globe at Night citizen-science program. So far this year the program has recorded over 20 thousand observations from all around the world to help scientists understand the impacts of light pollution on a global scale. The program started as a project initiated during the International Year of Astronomy in 2009 and has been going strong ever since. This month the featured constellation is Cygnus, the Swan, whose brightest star, Deneb, is one of the apexes in the Summer Triangle asterism. Deneb is the faintest and most northerly of the Triangle’s stars, but it can be easily seen even from the most urban locations. The rest of Cygnus extends toward the middle of the Summer Triangle, with the Swan’s head, Albireo, nearly at its center. This star is one of my favorite targets for small telescopes; it is an easily split double star with blue and gold components which I like to call the “Navy star”. Between Albireo and Deneb lie the other stars in the constellation. Suburban skywatchers should be able to see a cross-shaped grouping of stars that, with a little imagination, can be seen as a swan in flight. Pick a clear night to find Cygnus, then go to the Globe at Night Web App to record your observation.
From a dark location you should be able to see Cygnus in all its splendor. The swan seems to be “flying” along the path of the Milky Way, which seems to cleave into two parts along its path. This feature continues down to the horizon and is known as the Great Rift. While it has the appearance of being somewhat devoid of stars, it is actually an enormous cloud of cold, non-luminous gas and dust blocking the light from even more distant star clouds in our galaxy’s spiral arms. These dark clouds are a feature of the summer Milky Way, and they continue along the parts of the galaxy that can only be seen from more southerly climes. Indeed, the ancient Inca people and their relatives created much of their sky lore from the shapes of these dark features in the soft glow of the southern Milky Way. We northerners only get to see a small part of them.
I finally had my first really good evening for observing Jupiter. Due to its extreme southern declination it is very hard to see from my house during the brief time that he passes between my neighbor’s chimney and a large tree. Almost invariably the time when Old Jove is in the right place a cloud scurries in front of him. Such is the lot of the suburban astronomer. However, I was able to have a nice session with Jupiter using the Observatory’s 125-year-old 12-inch refractor, whose old glass still provides great views. The famous Great Red Spot was prominently featured, and the moon Europa was leading its shadow across the disc. You don’t need a big telescope to enjoy these features, though; a good four-inch scope should show these features quite nicely.
Saturn was next on my agenda after Jupiter. I can honestly say that even after decades of looking at the ringed planet through dozens of different telescopes there is still a certain sense of awe whenever I train the 12-inch on it. Yes, occasionally I will lapse into a state of disbelief that such an amazing sight appears in Nature.
I’m looking forward to the views of Mars that I’ll get this fall, but even now the red planet beckons. Mars now rises just before 11:00 pm, and you will have no trouble picking him out of the sparse stars of Autumn during the late night and early morning hours. Modest telescopes will show many of his enigmatic surface features and dazzling polar ice cap. Other than the Moon and Mercury, Mars is the only pother place in the solar system where you are looking at a solid surface.
Venus gets a pre-dawn visit from the Moon on the morning of the 15th. She is now moving through the heart of the rising Great Winter Circle, drifting among the stars of Gemini.
|The Summer Milky Way, imaged 2020 July 26 from Mollusk, Virginia
with a Canon EOS Rebel SL2 DSLR, 18mm @ f/5.6, composite of 12 90-second exposures at ISO 3200.
The Moon climbs northward along the ecliptic in the morning skies this week, passing through the rising autumnal constellations. Last Quarter occurs on the 11th at 12:45 pm Eastern Daylight Time. Early risers on the morning of the 9th get a nice treat as Luna poses just one degree south of the brightening planet Mars.
August is the month to look for meteors. In addition to an increase in the “background” count of random shooting stars, the annual Perseids meteor shower peaks at the end of the week. This display is one of the most consistent from year to year, and shower members can be seen from mid-July through August. This year the peak activity occurs on the nights of the 11th-12th and 12th-13th. A single observer at a dark location may be able to see around 60 shooting stars per hour starting at around 11:00 pm local time when the radiant, in the constellation of Perseus, climbs into the northeastern sky. The Perseids are particles that have streamed off of Periodic Comet 109/P Swift-Tuttle, which circles the Sun once every 133 years. The comet was co-discovered in 1862 by Horace P. Tuttle, one of the most prolific American comet seekers, at Harvard College Observatory. Tuttle had an interesting life and career, spending time at the U.S. Naval Observatory. Each year in August Earth intersects the orbit of the comet, running headlong into the debris sputtered off its surface each time it rounds the Sun, causing the annual display. Historical records indicate that the shower has been an ongoing event since at least the year 36 CE. You’re best time to catch them will be between 11:00 pm and 1:00 am, when the waning Moon rises to brighten the sky. The meteors are fast, flashing across the sky in mere seconds; the brightest ones leave persistent trains.
The waning Moon also means that it’s time once again to explore our home galaxy, the Milky Way. From dark skies the luminous band becomes apparent by around 10:00 pm local time. The densest part of the Milky Way is due south at this time, sandwiched between the stars of Scorpius and Sagittarius. Unfortunately, many people have never seen this subtle sky glow, and on first encountering it they mistake it for a terrestrial cloud. However, this cloud doesn’t move with respect to the stars, and it doesn’t take much optical aid to realize that it is comprised of uncountable numbers of stars. A steadily held pair of binoculars is enough to start to resolve the brighter patches and dark lanes that snake through them. Binoculars will also reveal that some of the brighter knots scattered among the star clouds are individual clusters of stars and glowing clouds of interstellar gas and dust. One of my favorite sights of summer is a prominent star cluster located between the two stars that form the “stinger” of the Scorpion and the “spout” of the Teapot asterism of Sagittarius. Known as Ptolemy’s Cluster or Messier 7, it is easily resolved in binoculars, and a small-aperture low-power telescope reveals a beautiful scattering of pale blue stars set against a background of millions of fainter ones. Sweep up the Milky Way from this cluster and you’ll encounter a dozen similar treats!
Jupiter is prominent in the southeastern sky as twilight fades. The giant planet crosses the meridian at around 11:30 pm, so you have plenty of time to get him focused in the telescope eyepiece. Jupiter offers the largest apparent disc of any of the planets, and you should be able to see his dark equatorial cloud belts in telescopes of 3-inch aperture. Almost any optical aid will reveal the planet’s four large Galilean moons, but a modest telescope will allow you to see their shadows cross the planet’s face. On the evening of the 7th we get a shadow “two-fer”, with Ganymedes’ shadow on the disc until 9:53 pm EDT and Io’s umbra entering transit at 10:13 pm.
Saturn follows Jupiter by about 10 degrees as they parade across the southern horizon. While they appear close in the sky, they are actually very far apart. Currently Old Jove is about 631 million kilometers (392 million miles) from Earth; Saturn is well over twice a far distant! In fact, we don’t really see either planet in “real time” since the speed of light is finite. Jupiter’s light takes 35 minutes to reach us, while Saturn’s glow takes just over 75 minutes!
Mars continues to brighten as he drifts through the stars of Pisces. His eastward progress is beginning to slow as he approaches opposition in the fall. He will spend the next few months in this general area of the sky, becoming very prominent by early October. He will get a close visit from the Moon before dawn on the 9th.
Venus continues to drift eastward among the rising winter stars in the gathering morning twilight. You should have no trouble spotting her in the east as she passes north of the prominent stars of Orion.