Skywatch Line for Friday, September 18th through Sunday, September 20th, 2020

This is Dudley Observatory’s Skywatch Line for Friday, September 18, through Sunday, September 20, written by Sam Salem.

On Friday, Sun rises at 6:39am and sets at 6:59pm; Moon rises at 7:51am and sets at 8:05pm. The Moon reaches perigee, the Moon’s closest point to Earth in its monthly orbit, on Friday. At that time, Moon travels away from the Sun at a maximum orbital speed. After sunset, spot the very slim crescent Moon sitting just above the western horizon, and a palm’s width to the upper right of Mercury. Find an unobstructed horizon in the direction of sunset. Look westward, near the sunset point on the horizon, for a pale crescent, some 45 minutes after sundown. The Moon and Mercury sit low in the west, sinking with the not-yet-visible stars of Virgo. The Moon and Mercury will both fit into the field of view of binoculars. Ensure that the Sun has completely disappeared from view before using them. This young Moon takes place just a few days before the Northern Hemisphere’s autumn equinox. At sunset on the autumn equinox, the ecliptic hits the horizon at its shallowest angle for the year.

Venus, at magnitude –4.2 in dim constellation Cancer, rises in deep darkness, two hours before dawn begins, in the east-northeast. Venus sits about 20 degrees below Pollux and Castor, in constellation Gemini. By the time dawn gets under way, Venus shines fairly high in the east. To Venus’ upper right is Procyon, in constellation Canis Minor. Venus and Procyon form a nearly equilateral triangle with Pollux above. Right, or lower right, of Procyon shines brighter Sirius, in constellation Canis Major. In a telescope, Venus continues to shrink slowly into the distance. It’s now about 18 arcseconds in diameter. As it rounds toward pass behind the Sun, it’s becoming more gibbous. It’s now 65% sunlit.

Mars shines big, bright, and close as it approaches its October 13th opposition. It rises in the east around the end of twilight, shining bright orange, at magnitude –2.2. Mars climbs higher through the evening and stands at its highest, and telescopic best, around 3am, beaming high in the south. It’s near the dim, 4th-magnitude, Knot of Pisces. Mars is becoming less gibbous, about 95% sunlit, as it approaches “full Mars” at opposition. In a telescope, look for its white South Polar Cap, now much shrunken as summer advances in Mars’s southern hemisphere.

Jupiter, at magnitudes –2.5, and Saturn, at magnitude +0.4, shine in the south in early evening and move to the southwest later in the night. Saturn remains 8 degrees to the left of Jupiter. Very high above the two planets shines Altair, in constellation Aquila. Altair is a white-hot star, 11 times as luminous as the Sun, and just 17 light-years away. Much closer below Jupiter after dark is the handle of the Sagittarius Teapot. The brightest top star of the Teapot handle is Sigma Sagittarii, or Nunki. At magnitude 2.0, Nunki is an even hotter blue-white star, 4.5 times the Sun’s diameter, 3300 times as luminous, and 230 light-years away.

This weekend, the delicate crescent will sink lower in the deepening twilight, leaving a dark sky overnight for deep sky observing. Use your scope to explore Andromeda Galaxy (M31), the triangle-shaped Triangulum Galaxy (M33), and the planetary Ring Nebula (M57) in the northern constellation of Lyra. Early in the evening, you may even catch 9th-magnitude Comet 88P/Howell, about 3.5 degrees west of globular cluster M80 in constellation Scorpius.

Skywatch Line for Wednesday, September 16th and Thursday, September 17th, 2020

This is the Dudley Observatory Skywatch Line for Wednesday, September 16th, and Thursday, September 17th, written by Louis Suarato.

The New Moon occurs at 7:00 a.m. Thursday. This is only about 26 hours before the Moon reaches perigee, it closest distance to Earth during this lunar cycle. Tides may be significantly higher, or lower, during this time. The Moon has little gravitational effect on water directly, because of water’s low mass. But, during the times of New Moons and Full Moons, the Moon’s gravitational pull causes the Earth to bulge underneath the oceans on the side facing the Moon, and also on the opposite side. As Earth rotates under those areas, we experience low tides. The sides of the Earth perpendicular to the Moon become elongated. As Earth rotates under those areas, we experience high tides.

Mars rises at 8:30 Wednesday night. The red planet continues to brighten as it approaches opposition on October 15th. Look about 13 degrees to the left of Mars to see the seventh planet from thew Sun, Uranus. You may be able to spot Uranus with the naked eye under optimal conditions, but a pair of binoculars offer better viewing. The distance between Earth and Uranus can be as close as 1.6 billion miles and as far as 1.98 billion miles. When you look at Uranus this week, it will be 1.77 billion miles away. Saturn and Jupiter shine 24 degrees over the southern horizon at astronomical twilight, when the Sun is 12 to 18 degrees below the horizon, and most stars can be seen. Astronomical twilight occurs at 8:36 p.m. Wednesday. The two gas giants set 40 minutes apart. Jupiter sets first at 58 minutes past midnight, and Saturn sets 1:38 a.m. Thursday. Take advantage of these moonless nights to observe the two planets before they get too low in the sky. There will be a bright International Space Station pass by the two large planets this Wednesday night. Look to the south-southwestern horizon at 8:13 p.m. Wednesday. Watch as the -2.8 magnitude ISS makes its way through Scorpius and Sagittarius before flying close by Jupiter and Saturn. The Space Station will then cross Capricornus before disappearing into Earth’s shadow in Aquarius. Venus rises at 2:59 Thursday morning. Look for M44, the Beehive Cluster, 13 degrees above Venus.

Skywatch Line for Monday September 14th and Tuesday September 15th, 2020

This is Dudley Observatory’s  Skywatch Line for Monday and Tuesday, September 14th and 15th.

The Sun sets at 7:06 PM; night falls at 8:42. Dawn begins at 4:59 AM and ends with the Sun rising at 6:36.

Monday’s Moon, in Leo, sets at 5:58 PM, and rises Tuesday, also in Leo, at 3:58 AM, 27 days old, only 3% illuminated and sets at 6:35 PM. Tuesday’s slim crescent lies 5° above Leo’s brightest star, Regulus.

Sagittarius contains Jupiter, Pluto and Saturn. Jupiter still rises first at 4:04 PM, shines with minus 2nd magnitude 43 arc-seconds in size, best observed a 10:32 PM and sets at 1:04 AM. Its earth-sized storm, the Great Red Spot is telescopically visible on Tuesday at 12:44 AM. Pluto rises next, at 4:26 PM, glows with 14th magnitude, appears as a tiny dot and sets at 1:27 AM. Saturn is next, rising at 4:32 PM, glimmering at zero magnitude, appears as 17 arc-seconds, is best observed at 9:06 PM and sets at 1:45 AM. Jupiter lies about 5° from Pluto and 8° from Saturn. Both Jupiter and Saturn are well placed for observation.

Mars, in Pisces, rises at 8:41 PM, glitters with minus 2nd magnitude, appears 21 arc-seconds, 95% lit, and best observed at 3:09 AM. The Red Planet continues to brighten and enlarge in advance of its October Opposition.

Neptune, an outer Gas Giant planet, rises in Aquarius at 7 PM, glows with 7th magnitude, 2 arc-seconds, and best observed at 12:43 AM. Neptune just passed Opposition last Friday; this means it is brightest and best situated for observation for the year. Uranus, also a Gas Giant, rises in Aries, at 8:54 PM, sparkles with 5th magnitude, 3 arc-seconds and best viewed at 3:52 AM.

Pluto, Uranus and Pluto all require detailed charts available from astronomy media. Mars, Uranus, Neptune and Venus set during daytime.

Venus, in Cancer, is the last to rise at 2:56 AM, blazing with minus 4th magnitude, 17 arc-seconds, 66% lit. Venus appears about 16° above the Moon at 5 AM.

If you live away from sources of light pollution, the next two weeks are special. The inner Solar System is full of dust. These particles vary from small pebbles to smoke particles. When the position of the Sun and the ecliptic are right, a faint glow of light may appear in the East. This phenomenon is called Zodiacal Light. It is best seen about a half hour after twilight ends, or 2 hours before dawn begins. This time of the year, it appears before Dawn. The scattering of sunlight off of dust grains, which are positioned between the Sun and Earth, cause it. However, Moonlight, atmospheric pollution or haze will erase the effect. If you are lucky, you will see a pillar of light rising from the horizon in the direction of the Sun. Binoculars or telescopes do not work on this object, only the naked eye. A similar effect called Gegenschein, is located in part of the sky opposite the Sun. This faint pillar of light is best seen at midnight during the depths of winter.

Clear Skies

Joe Slomka

Skywatch Line for Friday, September 11 through Sunday September 13, 2020

This is Dudley Observatory’s Skywatch Line for Friday, September 11, through Sunday, September 13, written by Sam Salem.

On Friday, Sun rises at 6:31am and sets at 7:11pm; Moon sets at 3:34pm. When the waning crescent Moon rises shortly after midnight on Friday, it will be positioned several degrees to the west of the large open star cluster Messier 35, or the Shoe-Buckle, in constellation Gemini. Later at night, the Moon’s orbital motion will carry it closer to the cluster, bringing it just a finger’s width to the right of M35 before dawn. Hide the bright Moon, just beyond the right edge of your binoculars’ field of view, to see the cluster’s stars more easily. On Sunday, look for the waning crescent Moon and Venus to adorn the eastern predawn/dawn sky. You might even be able to view them after sunrise, or in daytime sky, if you know where to look.

On Friday, Neptune will be directly opposite the Sun in the sky. At opposition, Neptune will be closest to Earth, almost 4 light-hours, or 28.9 Astronomical Units from Earth. Because Earth is, more or less, between Neptune and the Sun around now, Neptune is rising in the east around the time of sunset, climbing highest up for the night around midnight and setting in the west around sunrise. Neptune is the only major solar system planet that’s absolutely not visible to the unaided eye. You’ll need at least binoculars to see Neptune in front of the constellation Aquarius. Neptune will shine at a slightly brighter magnitude 7.8. Around opposition, Neptune’s disk size will grow to 2.4 arc-seconds. Throughout September, Neptune will be located among the stars of northeastern Aquarius, about two degrees to the left of the naked-eye star Phi (φ) Aquarii. Though faint, Phi Aquarii, is easily visible to the eye alone on a dark night. The moon-free evening hours offer a dark sky for viewing Neptune and Phi Aquarii. They are so close together on the sky’s dome at present that the two readily fit within a single binocular field. You might see them together in a low-powered telescope, with blue-green Neptune offering a color contrast to the ruddy tint of Phi Aquarii. Neptune is nearly 30 times fainter than the star Phi Aquarii.

On Saturday, Jupiter will appear to stop moving with respect to the distant stars, marking the end of a westward retrograde loop that began in mid-May. On the following nights, Jupiter will appear to resume its regular eastward motion in northeastern Sagittarius and will begin to reduce its eight-degree separation from Saturn.

Algol, the Demon Star, or Beta Persei, in constellation Perseus, is among the most accessible variable stars for stargazers. Algol’s naked-eye brightness dims noticeably for about 10 hours once every two days, 20 hours and 49 minutes because a dim companion star orbiting nearly edge-on to Earth crosses in front of the much brighter main star, reducing the total light output we receive. On Sunday, at 9:08pm, Algol will reach its minimum brightness of magnitude 3.4. At that time, for observers in our area, the star will sit 12 degrees above the northeastern horizon. Five hours later, at 2:08am, Algol will be high in the eastern sky, and will have brightened to its usual magnitude of 2.1. Draw an imaginary line from star Gamma Cassiopeia through star Ruchbah, in constellation Cassiopeia, to locate constellation Perseus then Algol.

Skywatch Line for Wednesday September 9th and Thursday September 10th, 2020

This is the Dudley Observatory Skywatch Line for Wednesday, September 9th, and Thursday, September 10th, written by Louis Suarato.

The 53% illuminated, waning gibbous Moon rises at 11:08 p.m., Thursday in the constellation Taurus among the stars of the Hyades cluster. Look for Taurus’ brightest star, Aldebaran, 7 degrees to the lower left of the Moon, and the Pleiades star cluster, M45, above. The Last Quarter Moon occurs at 5:28 a.m., Thursday. Jupiter and Saturn remain in the sky until they set at 1:25 a.m., and 2:06 a.m., respectively. At 10:58 p.m. Wednesday, Jupiter’s moon, Europa, begins to be occulted by the planet. The Great Red Spot transits at 4 minutes past midnight Thursday. At 4:07 a.m., Europa’s eclipse ends. Mars rises at 8:59 p.m. in Pisces. Until September 10th, Mars has been moving eastward against the background stars. When Mars reaches its stationary point on Thursday, it will appear to stop and begin to move westward, or retrograde motion, against the background stars. The cause of this appearance is one planet passing another during their orbits. Venus rises in Cancer at 2:47 a.m., 4 degrees to the right of M44, the Beehive Cluster.

Open star clusters are groups of gravitationally bound stars formed from the same molecular cloud and approximately the same age. There have been more than 1,100 open star clusters discovered in the Milky Way galaxy. Some of the more prominent open star cluster are mentioned above. These have been observed for centuries by scientists who study stellar evolution. There are 27 open star clusters listed in Messier’s catalogue.

There will be an extremely bright International Space Station pass over our region Wednesday morning. Look to the northwestern horizon for the -3.6 magnitude ISS beginning at 5:48. The ISS will pass Cygnus and Cepheus before crossing Cassiopeia. The Space Station continues past Auriga’s brightest star, Capella, before sailing through the Gemini twins. The ISS flies below Venus and crosses Procyon in Canes Minor before disappearing into the southeastern horizon.

Skywatch Line for Monday September 7 and Tuesday September 8th, 2020

This is the Dudley Observatory’s Skywatch Line for Monday and Tuesday, September 7th, Labor Day, and 8th.

The Sun sets at 7:18 PM; night falls at 8:56. Dawn begins at 4:50 AM and ends with the Sun rising at 6:28.

The 20-day-old Moon rises in Aries at 10:03 PM, 72% illuminated and sets at 12:33 PM, Tuesday. Tuesday’s Moon rises in Taurus at 10:32 PM, 63% lit and sets at 1:34 PM, Wednesday.

Sagittarius continues to house Jupiter, Pluto and Saturn. Jupiter rises at 4:32 PM, is best observed at 9 PM, when it is due South and sets at 1:32 AM, Tuesday. Jupiter blazes with minus 2nd magnitude, appears 43 arc-seconds in size, and is 23° high at 9 PM. Monday, telescopic observers can witness the moon Io disappear behind the planet at 8:23 PM and reappear at 11:48 PM. Pluto rises next at 4:54 PM, glowing with 14th magnitude, appearing as a tiny dot, 24° high and setting at 1:55 AM. Third, Saturn rises at 5 PM, shining with zero magnitude, appearing 17 arc-seconds in size 25° high and setting at 2:13 AM. Jupiter and Saturn are gradually closing, in preparation for a December conjunction.

Aquarius is the residence of Neptune and Minor Planet 1Ceres. Neptune rises at 7:28 PM, shining with 7th magnitude, 2 arc-seconds, 42° high at Midnight and best observed at 1 AM. 1Ceres rises at 7:02 PM, is best observed at 11:25 PM, 22° high and sets at 3:47 PM. Ceres lies about 21° below Neptune. Sky charts aid the observer in locating these dim members of our Solar System.

Red Planet Mars continues to brighten and grow larger in our instruments. Rising in Pisces at 9:10 PM, it sparkles with minus 2nd magnitude, 20 arc-seconds in size, 41° high at Midnight, is best observed at 3:37 AM. Uranus, in Aries, rises at 9:22 PM, glimmers with 5th magnitude, 40° high at Midnight and best observed at 4:20 AM. Note that Mars, Uranus, 1Ceres and the Moon all occupy the eastern part of the night sky. Also note that Mars, Uranus, Neptune and Venus all set during daytime.

Venus is the last planet to rise, in Cancer, at 2:46 AM. It blazes with minus 4th magnitude, 18 arc-seconds, 2° high at 3 AM and appears about 62% lit.

Variable star Algol, in Perseus, experiences its minimum at 2:30 AM on Tuesday. However, the nearby brilliant Moon may interfere with observation.

Since Monday is Labor Day, let us study the 12 labors of Hercules, now 23° high at 11 PM in the western sky. His story is long and convoluted; in short, he killed his wife and children and was seeking redemption by consulting the famed Oracle at Delphi. The Oracle referred him to Eurystheus, who imposed 12 tasks before Hercules would be accepted among the gods. He had to: strangle the Nemean Lion, chop off the 9 heads of the Hydra, return a stag with golden horns, capture and return a giant boar, clean out the Augean stables (which weren’t cleaned for years), drive away the Stymphalian birds, go to Crete to return a bull, drove off the man-eating mares of King Diomedes, capture the girdle of the Amazon Hippolyta, return the cattle of Geryon, retrieve the Golden Apples and finally, go to Hades to free Theseus and bring to Earth the Cerberus, a three-headed dog that guarded Hades. Accomplishing these dangerous challenges restored his standing with the gods and guaranteed his place in the heavens.

Clear Skies,

Joe Slomka

Skywatch Line for Friday, September 4 through Sunday, September 6, 2020

This is Dudley Observatory’s Skywatch Line for Friday, September 4, through Sunday, September 6, written by Sam Salem.

On Friday, Sun rises at 6:24am and sets at 7:24pm; Moon sets at 8:31am and rises at 8:53pm. The waning gibbous Moon rises around the end of twilight on Friday evening. Once it’s up, watch for Mars, bright at magnitude -2.0, to rise about a fist-width or a little more to the Moon’s lower left. They climb high as evening grows late. Once they’re up, they will be out for rest of the night. On Saturday, the Moon and Mars rise together in the east, about a half hour after the very end of twilight. They’ll be only about 1 degree apart or less. By dawn Sunday, Moon and Mars stand high in the southwest, 2 or 3 degrees apart.

Venus, at magnitude –4.3 in constellation Gemini, rises two hours before dawn begins, in the east-northeast. By the time dawn gets under way, Venus blazes brightly high in the east. Venus stands just a little lower each morning, while the background stars move rapidly to the upper right as the days progress. In a telescope Venus continues to shrink while becoming slightly gibbous.

Jupiter and Saturn shine in the south in early evening. Jupiter is the brightest, and Saturn sits 8 degrees to its left. They’re perfectly horizontal right around the end of twilight. Lower right of Jupiter after dark is the handle of the Sagittarius Teapot. On Saturday, Jupiter’s Great Red Spot should transit Jupiter’s central meridian around 10:18pm.

As the Moon rises in the east on Friday evening, turn your focus to the west. About 9.5 degrees northwest of Kaus Borealis, the top of the Sagittarius Teapot’s lid, is M23, or NGC 6494. This open cluster of stars is easy to spot with binoculars or a small scope, spanning 27′ and shining at magnitude 5.5. It contains at least 170 stars that, while young at 220 million years, make them quite old as far as open clusters go. In binoculars, M23 will likely appear only as a smudge with a few individual stars visible. You’ll need a telescope to begin resolving most of its stars. The particularly bright star in the cluster’s northwest is not actually a member, but a magnitude 6.5 foreground star called HIP 87782.

Mercury and Venus have no moons, most likely because they are too close to the Sun, which would make any moon in an unstable orbit to be captured by the Sun’s gravity. What would Earth be like with no Moon? Earth without its, relatively large, nearby, Moon would be a very different world. In addition to the moonlight we enjoy at moonlit nights, the Moon keeps Earth at a decent pace and tilt. The Moon stabilizes Earth to keep that 23.5 degrees tilt that makes for mild seasons. The climate of the Earth is sensitively dependent on that tilt of the Earth’s axis. The Moon and Sun together cause the tides. If we’d never had a Moon, we’d still have tides, but they wouldn’t be as strong. Without its relatively large Moon, Earth would spin faster, and days would be shorter. If there is no Moon, ocean water would disperse from middle of the Earth to the poles, due to lack of Moon’s gravitational pull. Wind and storms would increase, due to Earth’s faster spin.

Skywatch Line for Wednesday September 2nd and Thursday September 3rd, 2020

This is the Dudley Observatory Skywatch Line for Wednesday, September 2nd, and Thursday, September 3rd, written by Louis Suarato.

The 99.4% illuminated, waning gibbous Moon rises at 8:12 p.m. in the constellation Aquarius. The Moon will be positioned between Mars, to the east, and Saturn and Jupiter, to the south. Venus rises at 2:39 a.m. between Gemini and Cancer. Use binoculars to find M44, the Beehive Cluster, 10 degrees to the lower left of Venus. At the estimated distance of between 520 and 610 light-years, M44 is one of the closest open star clusters. The stars within the Beehive Cluster are estimated to be about 600 million years old. In 1609, Galileo telescopically resolved 40 stars within this cluster, but modern telescopes help put the total closer to 1,000 stars.

There will be a moderately bright International Space Station appearance in the Wednesday morning sky. The -1.8 magnitude ISS will emerge from Earth’s shadow in mid-sky, below the Little Dipper, at 4:11 a.m., traveling north to east. The ISS will continue toward the Big Dipper, before disappearing into the northeastern horizon below the rising Beehive Cluster.

September 2nd marks the beginning of the winter solstice for the northern hemisphere on Mars. Earth’s seasons are determined by its axial tilt toward, and away from the Sun, instead of its distance from the Sun during its orbit. Like Earth, Mars is also tilted at its axis. While the Earth is tilted at 23.5 degrees, Mars has an axial tilt of 25 degrees. Also, Mars has a more eccentric orbit than Earth’s, adding to the determination of the seasons. Over the Martian year, Mars’ distance from the Sun varies from 1.64 Astronomical Units (the average distance of Earth to the Sun) to 1.36 Astronomical Units. This significant variation, along with the 25 degree axial tilt, causes greater seasonal differences than we experience. It is estimated that Mars receives 40% more energy from the Sun during perihelion than it does during aphelion.

Skywatch Line for Monday August 31st and Tuesday September 1st, 2020

This is the Dudley Observatory’s Skywatch Line for Monday and Tuesday, August 31th and September 1st, written by Joe Slomka.

The Sun sets at 7:31 PM; night falls at 9:11. Dawn begins at 4:40 AM and ends with the Sun rising at 6:21.

Monday’s Moon rises at 7:14 PM in Capricornus, 98% illuminated and sets at 5:25 AM, Tuesday. Tuesday’s Full “Corn” Moon rises at 7:43 PM in Aquarius and sets at 6:29 AM, Wednesday.

Sagittarius continues to house Jupiter, Saturn and Pluto. Jupiter is the first to rise at 5 PM, glaring with minus 2nd magnitude, 44 arc-seconds in size, is best observed at 9:28 PM and sets at 2 AM. Telescopic observers can see the Great Red Spot (a giant earth-sized storm) at 11:10 PM and also see Jovian moon Ganymede disappear at 8:34 PM and reappear at 11 PM. Both events take place Monday evening. During September, Jupiter dims and shrinks a little in our telescopes. Pluto rises next at 5:22 PM, glows with 14th magnitude, appears as a tiny dot (requiring detailed sky charts), 11° high and sets at 2:23 AM.

Saturn is next, rising at 5:29 PM, zero magnitude, 17 arc-seconds, and best observed at 10:03 PM and sets at 2:42 AM. It’s beautiful ring system is tipped 23°. Both Jupiter and Saturn are perfectly situated for your enjoyment.

Aquarius houses Ceres and Neptune. Minor Planet 1Ceres rises at 8:38 PM, shining with 7th magnitude; 11° high, it is best observed at 1:05 AM and sets during Dawn. Monday evening, it lies above the bright star Fomalhaut and below the Moon. Neptune rises at 7:55 PM, gleaming with 7th magnitude, 2 arc-seconds, is best seen at 1:39 AM, 41° high and sets daytime.

Uranus, in Aries, rises at 9:50 PM, shines with 5th magnitude, 3 arc-seconds in size, is best observed at 4:48 AM and also sets daytime. Charts for Neptune, Ceres and Uranus are available from astronomical media.

Red Planet Mars rises in Pisces at 9:36 PM, twinkles with minus 1st magnitude, 19 arc-seconds, 91% lit and is best observed at 4:03 AM. Mars continues to brighten in September, from minus 1.8 to minus 2.5 magnitude and increasing in size from 19 arc-seconds to 22 arc-seconds.

Finally, Venus rises in Gemini at 2:38 AM. September, Venus shrinks from 19 arc-seconds to 15 arc-seconds, but goes from 60% to 71% lit; it blazes with minus 4th magnitude and sims slightly.

If we look south at about 10:00 PM, a hazy white band of light seems to stretch from the North Pole to horizon. This band is commonly called “The Milky Way”. Examination of the Milky Way with binoculars or telescopes reveals it to be a continuous band of stars or clouds of dust or gases. Our galaxy is a gigantic pinwheel, with several arms. Our planet is located in one of these arms. When we look at the Milky Way, we are seeing through this arm out into space. From Lyra to Sagittarius the Milky Way seems to divide in two. A giant dust cloud causes this “Great Rift”. We can see these dust clouds on other galaxies. If we follow the Milky Way to the horizon, we come upon the constellation Sagittarius. The center of our galaxy is located in that constellation, but we cannot see it due to dense star and dust clouds.

Skywatch Line for Friday August 28 through Sunday August 30, 2020

This is Dudley Observatory’s Skywatch Line for Friday, August 28, through Sunday, August 30, written by Sam Salem.

On Friday, Sun rises at 6:16am and sets at 7:36pm; Moon sets at 1:17am and rises at 5:11pm. On Friday evening, the waxing gibbous Moon will sit just two finger widths below Jupiter with Saturn to their left. Both objects will fit within the field of view of binoculars. During the night, the diurnal rotation of the sky will move the Moon to Jupiter’s left by the time they set, at about 2:30am. On Saturday evening, the Moon will hop east to sit a palm’s width to the lower left of Saturn. During the night, the diurnal rotation of the sky will lift the Moon higher than Saturn.

On Sunday night, the terminator on the waxing gibbous Moon will fall just west of Sinus Iridum, the Bay of Rainbows. Sinus Iridum is almost craterless but hosts a set of northeast-oriented “wrinkle ridges” that are revealed at this lunar phase. The circular 155-mile diameter feature is a large impact crater that was flooded by the same basalts that filled the much larger Mare Imbrium to its east, forming a rounded “handle-shape” on the western edge of that mare. The “Golden Handle” effect is produced by way the slanted sunlight brightly illuminates the eastern side of the prominent Montes Jura mountain range surrounding the bay on the north and west. And by a pair of protruding promontories named Heraclides and Laplace to the south and north. Use a lunar map to help you locate these Moon features.

Venus beams in front of the great big lasso of stars known as the Winter Circle. For the next several days, Venus shines at the eastern border of the Winter Circle, midway between the Procyon, the Little Dog star, and the Gemini stars, Castor and Pollux. The Winter Circle dwarfs constellation Orion, the Hunter, which only makes up the southwest, or lower right portion of the Winter Circle. If you are acquainted with Orion, this constellation presents a great jumping off place for circumnavigating this Winter circle of stars. From Rigel in Orion, go to Aldebaran in Taurus, to Capella in Auriga, to Castor and Pollux in Gemini, to Procyon in Canis Minor, to Sirius in Canis Major. In late August, the Winter Circle returns to the morning sky. But we still won’t see the Winter Circle in the evening sky for months to come.

On Friday, the dwarf planet, formerly asteroid, Ceres will reach opposition, its closest approach to Earth for the year. On the nights around opposition, Ceres will shine with a peak magnitude of 7.2, well within reach of binoculars and backyard telescopes. Ceres will be situated only palm’s width above the bright naked-eye star Fomalhaut, in constellation Piscis Austrinus. Both objects will easily fit within the field of view of binoculars. Ceres will already be climbing the southeastern sky after dusk. It will reach its highest elevation, and peak visibility, over the southern horizon after 1am.

The Great Square of Pegasus is a great jumping-off point for finding Andromeda galaxy, or Messier 31. The Great Square of Pegasus sparkles over the eastern horizon at about 9:00pm in late August and early September. Locate the Great Square of Pegasus in your eastern sky. You’ll see the constellation Andromeda as two streamers of stars jutting up from the uppermost Great Square star. The two streamers mimic the shape of a cornucopia or a bugle. Go to the second star upward on each streamer, Mirach and Mu Andromedae. Draw an imaginary line from Mirach through Mu, going twice the Mirach/Mu distance, you locate the Andromeda galaxy. On a dark night, the Andromeda galaxy looks like a faint, blurry patch of light.