Skywatch Line for Wednesday, January 2nd, and Thursday, January 3rd, 2019

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

The 11% illuminated, waning crescent Moon sets at 2:21 p.m., Wednesday. Mars, in the constellation Pisces, begins January at magnitude 0.50, but will fade to magnitude 0.90 at month’s end. Mars Insight, NASA;s robotic lander, recently placed the first seismometer on the planet, enabling scientists to detect Marsquakes. The pre-dawn planets of Mercury, Jupiter and Venus, are joined by the crescent Moon. Thursday morning, the 6% illuminated, waning crescent Moon will be 3 degrees to the left of Jupiter. Venus is descending, while Jupiter is climbing each day, and the two planets will pass each other on January 22nd.

Earth reaches perihelion, its closest approach to the Sun during 2019, on Thursday at midnight. The Sun will be 91,403,724 miles away when Earth’s elliptical orbit brings it to its closest approach. During aphelion, which occurs every year around July 4th, Earth is approximately 3.1 million miles further away from the Sun than it is during perihelion. This change in distance isn’t enough to cause a seasonal change to our planet. The 23.5 degree tilt of our planet’s axis is what causes the seasonal changes to the hemispheres. During perihelion, when Earth is closest to the Sun, its northern hemisphere is tilted away from the Sun, lengthening the time it takes for sunrays to reach Earth. When the northern hemisphere tilts toward the Sun in July, the more direct sunrays warm the upper half of the planet.

Comet 46P/Wirtanen is still providing excellent binocular and telescope views. Now shining at 4th magnitude, this comet is heading back toward Jupiter’s orbit. Thursday night, you can use the top two stars forming the Big Dipper’s bucket to find Comet 46P/Wirtanen. Follow the two stars, Megrez and Dubhe, toward Capella. You’ll find the bluish-green comet about a third, to half, of the way to Capella.

Skywatch Line for Monday and Tuesday, December 31st, 2018 and January 1st, 2019

This is the Skywatch Line for Monday and Tuesday, December 31st and New Year’s Day (January 1st).

The Sun sets at 4:31 PM; night falls at 6:13. Dawn breaks at 5:44 AM and ends with the Sun rising at 6:54 AM.

Mars is the only bright planet visible from Dusk to Midnight. Mars lies sandwiched between Neptune and Uranus. Neptune, in Aquarius, lies about 15º below Mars and flickers with minus 8th magnitude and only 2 arc-seconds in size. Neptune sets at 9:52 PM. Mars, in Pisces, shines with zero magnitude, shrinks to 7 arc-seconds in size and appears about 87% lit. The Red Planet is best observed at 5:14 PM and sets at 9:21. Uranus shares Pisces with Mars. It glows with 5th magnitude and appears about 6 arc-seconds in size. It is best observed at 7:01 PM and sets at 1:42 AM. Both Uranus and Neptune require finder charts from various astronomical media.

Comet 46P/Wirtanen resides in the dim constellation Lynx. It is fading to 10th magnitude as it retreats from Earth. Again, finder charts will assist the observer.

Dawn brings the arrival of brilliant planets and the Moon. The Moon occupies Libra on both nights. It appears about 19% lit on Tuesday morning and 12% on Wednesday; it dims from minus 7th magnitude on Tuesday to minus 6th magnitude, Wednesday.

Venus shares Libra with the Moon, appearing about 47% illuminated and shining with minus 4th magnitude, having risen at 3:37 AM. Jupiter, rising at 5:16 AM, lies about 18º below Venus in Ophiuchus, glares with minus 2nd magnitude and appears about 32 arc-seconds in size. Mercury, also in Ophiuchus, rises about 6:18 AM, appears about 90% lit and blazes with minus zero magnitude. Jupiter may be too low for useful observations, and Mercury needs an unobstructed horizon to be seen.

Monday night will find most people watching a manmade star fall in Times Square. Astronomers will be watching something else at the same time. The New Horizons spacecraft, having flown past Pluto, will fly by another, even more distant member of our Solar System, asteroid 2014MU69, nicknamed Ultima Thule. This is the furthest heavenly body studied. Ultima Thule is about 20 miles in diameter. New Horizons will zoom by, taking pictures and measurements, three times closer than when it visited Pluto. NASA plans live coverage starting 12:15 AM, Tuesday on various NASA channels, like NASA TV, NASA.gov, etc. However, if the government shutdown continues, you can watch the flyby on the Johns Hopkins Applied Physics Laboratory You Tube channel.

Tuesday is, of course, New Year’s Day. Other cultures celebrate different days. For some, it is the Spring Equinox, others the Winter Solstice. Ancient Egyptians marked the rising of the star Sirius. Chinese celebrate New Year’s between January 20th and February 20th due to a lunar calendar. New Year’s Day also varies in the lunar Islamic calendar. Western calendars begin on January First – thanks to Julius Caesar. The Roman calendar was a mess; it contained 354 days. Extra months had to be inserted to keep in step with the Sun. While Caesar courted Cleopatra, he met her astronomer, Sosigenes, who recommended calendar reform. Caesar adopted those suggestions. On January First 45 BC, the new calendar became effective. It called for 365 days and twelve months. A leap day would be added every four years, to keep the calendar in sync with the Sun. With minor changes, this is the calendar we now use.

Skywatch Line for Friday, December 28 through Sunday, December 30, 2018

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

On Friday, the Sun rises at 7:26am and sets at 4:29pm; the waning gibbous Moon rises at 11:42pm and sets at 11:45am. The Moon reaches last-quarter phase on Saturday at 4:34am. Watch the Moon in the vicinity of Spica, the constellation Virgo’s one and only 1st-magnitude star, on Saturday and Sunday.

Mars, at magnitude 0.4, is the sole planet residing in the evening sky. Mars continues its eastward travel, prolonging its descent into twilight. Mars will linger at dusk until spring transitions to summer. Venus, the “morning star”, is gleaming at magnitude –4.7. It rises around 3:35am and climbs to an altitude of nearly 20 degrees before the first hint of morning twilight. Next to rise is magnitude –1.8 Jupiter. It clears the southeast horizon around 5:30am. Jupiter doesn’t get high enough for viewing in a scope just yet. Mercury, at magnitude –0.4, rises around 6:05am. The innermost planet is nearing the end of its most favorable appearance for this year. On Monday morning, step outside to enjoy a special view in the east before sunrise. The Moon, Venus, Jupiter, and Mercury are arrayed in a tidy line angled above the southeast horizon. In their order from top to bottom, you’ll see the waning crescent Moon, Venus, Jupiter, and Mercury. That also happens to be their order in brightness. The best time to take in the scene is roughly 45 minutes before sunrise. Mercury is the faintest of these worlds and the lowest in the sky. It’ll be the toughest to spot. To catch it, you’ll need an unobstructed view to the southeast. Look for Mercury close to the horizon, along line with the Moon, Venus and Jupiter, with the unaided eye or binoculars.

Evenings over this weekend are free of moonlight, giving a change to enjoy some of the late autumn’s deep-sky objects, including M33. Although catalogued as a magnitude 5.7 object, the spiral galaxy M33, in constellation Triangulum, can be difficult to observe in a light-polluted sky. The galaxy is both large, more than one degree across, and nearly face-on. Its light is spread out across a substantial area. In a telescope, M33 can be seen as a pale cloud. Its surface brightness is so low that the galaxy simply blends in with the background sky glow. In ideal conditions, far from town, M33 can be glimpsed with the naked eye, but from the suburbs it’s often hard to detect even in a good-sized telescope. M33 is one of the few galaxies that have their own built-in deep-sky objects. The most attracting of these is a knot of nebulosity lying northeast of the galaxy’s central hub. Listed as NGC604, this little blob can be spotted with a 4-inch scope in less-than-pristine skies. You will need to boost the magnification well beyond what you would use to view M33.

Sir Arthur Stanley Eddington, the English astrophysicist and mathematician, was born on December 28, 1882. He is known for his work on the motion, distribution, evolution and structure of stars. In 1917, he was one of the first to suggest, conversion of matter into radiation powered the stars. Sir Eddington interpreted Einstein’s general theory of relativity, and in 1919 he led a solar eclipse expedition, which confirmed the predicted bending of starlight by gravity. He developed an equation for radiation pressure. In 1924, he derived an important mass-luminosity relation. He also studied pulsations in Cepheid variables, and the very high densities of white dwarfs.

Skywatch Line for Wednesday, December 26th, and Thursday, December 27th, 2018

This is the Dudley Observatory Skywatch Line for Wednesday, December 26th, and Thursday, December 27th, written by Louis Suarato.

The 80% illuminated, waning gibbous Moon sets at 10:30 Wednesday morning. The Moon rises again at 9:10 p.m. in the constellation Leo. The bright star to the upper right of the Moon is Regulus, Leo’s brightest. Look for Mars, the night’s only easily visible planet, about 45 degrees above the southern horizon after sunset. The morning sky features three planets. The brightest is Venus, which rises at 3:32 am. Jupiter rises next at 5:33, followed by Mercury, 25 minutes later. Look over the southeast horizon before sunrise to see all three planets.

The asterism known as The Winter Circle, or Winter Hexagon, is comprised of the stars Rigel, Aldebaran, Capella, Pollux, Procyon, and Sirius. Rigel is the brightest star in the constellation Orion, and the seventh brightest star in the sky, occasionally being outshone by Betelgeuse. It is estimated to be between 79 and 115 times the Sun’s radius. Rigel is 863 light-years away, and shines at magnitude 0.15. Aldebaran is the brightest star in Taurus, and the fourteenth brightest star in the sky. It is 65 light-years from the Sun, about 44 times as large, and shines at magnitude 0.85. Capella is Auriga’s brightest star, and the sixth brightest overall. It is 42.9 light-years away, and this quadruple star system’s two yellow giant stars are 2.5 times as massive as our Sun. Capella shines at magnitude 0.05. Pollux is the brightest of the stars in Gemini and, at the distance of 34 light-years, is the closest giant star to the Sun. Pollux is about nine times the size of the Sun, and shines at magnitude 1.15. Procyon in Canis Minor, is the eighth brightest star in the sky, shining at magnitude 0.40. This star is the eight brightest in the sky, and is 11.46 light-years away, making it one of Earth’s closest stellar neighbors. Sirius is Canis Major’s brightest, and at magnitude -1.45, the brightest in our sky. This binary system is 8.6 light-years away, and contains two of the eight nearest stars to the Sun.

Skywatch Line for Monday and Tuesday, December 24th and 25th, 2018

This is the Skywatch Line for Monday and Tuesday, December 24th and 25th.

The Sun sets at 4:26 PM; night falls at 6:08. Dawn begins at 5:42 AM and ends with the Sun rising at 7:24.

Mars is the only easily identified planet in our evening sky. The Red Planet shines with zero magnitude in Pisces, appears almost 87% illuminated and about 8 arc-seconds in size. It lies roughly 44º high in the southern sky. It is best observed at 5:25 PM and sets at 11:19 PM.

Neptune, in Aquarius, is no longer close to Mars, but lies nearly 11º west of Mars. Neptune shines with 8th magnitude, is a tiny 2.3 arc-seconds in size and lies 40º high in the South. It is highest at 4:44 PM and sets at 10:19 PM. Uranus, in Pisces, is the other difficult planet. It is brighter at 5th magnitude and is a larger 3.6 arc-seconds in our telescopes. Uranus shares Pisces with Mars, but is at the opposite end of the constellation. Uranus, near the star Omicron Piscium, is best observed at 7:28 PM and sets at 2:10 AM. Both planets require finder charts from astronomical media.

The waning 17-day-old Moon rises in Cancer at 6:51 PM, Monday. It blazes at minus 11th magnitude and appears 92% lit. Tuesday at Midnight, it is less than a degree from M44 (The Beehive). The Moon’s glare will hinder the observer from seeing the star cluster that night, but the observer should remember where it was and check the next night. The Moon sets at 2:27 AM, Tuesday, but rises at 8:05 PM in Leo and sets at 3:26 AM, Wednesday.

The variable star Algol, in Perseus, has minimum brightness at 9:17 PM Tuesday. Sky watchers should begin monitoring the star 2 hours before minimum through to 2 hours after the minimum.

Comet P/46 Wirtanen is now retreating from Earth. It travels about 4º per day. It is quite high in the sky and reported to be naked-eye visible. It was closest to the bright star Capella in Auriga and is moving northeastward. Wirtanen should appear as a greenish haze, without a tail. Finder charts assist the comet chaser.

Venus, in Libra, rises at 3:32 AM, blazes with minus 4th magnitude and appears about 44% lit. By Dawn, it is approximately 20º high in the southeast sky and at Civil Dawn it is 28º high. Jupiter, in Ophiuchus, returns to our skies and rises at 5:36 AM and, by Civil Dawn, 10º high. Jupiter shines with minus 1st magnitude and is a large 31 arc-seconds in our instruments. Jupiter acts as a guide to Mercury, also in Ophiuchus, which rises at 5:55 AM and is 4º below Jupiter. Mercury appears 86% lit and glows with minus zero magnitude.

This time of the year was dedicated to Saturn, the Roman God of Harvests. A series of feasts were held during the week of the Winter Solstice – the Saturnalia. Saturn was depicted as a jolly old man. People decorated evergreen trees. Candles were lit everywhere. Houses were decorated with wreaths and Holly. Decorated cookies were baked. People wore red peaked hats, similar to the “Santa hats” of today. Banquets were held both in honor of the harvest and wishing for a prosperous new year. Gifts were exchanged: dolls for the children, candles and fruits for adults. Donations and benefits were held for the poor. Saturnalia was an official government holiday. The holiday was so popular that Christians moved the feast of Christ’s birth to compete and adopted many of the symbols and traditions of this pagan feast.

The Dudley Observatory and Albany Amateur Astronomers wish their followers Happy Holidays.

Skywatch Line for Friday, December 21 through Sunday, December 23, 2018

This is Dudley Observatory’s Skywatch Line for Friday, December 21 through Sunday, December 23, written by Sam Salem.

On Friday, the Sun rises at 7:23am and sets at 4:25pm; the waxing gibbous Moon rises at 3:47pm and sets at 5:52am. The full Moon occurs on Saturday at 12:49pm. The lunar disk is 1.1 degrees north of 1st-magnitude star Aldebaran, the Taurus constellation’s brightest star, at roughly 4am on Friday. The winter solstice occurs this Friday at 5:23pm which marks the official start of winter in the northern hemisphere, the Sun’s southernmost point in our sky for the year. This month’s full Moon happens less than one day after the December solstice. The last time the December solstice and full Moon happened less than one day apart was in 2010, and the next time will be in 2029.

Mars, at magnitude 0.3, is the only planet shining in the evening. The red planet is well past its summer prime as it slowly makes its way eastward through constellation Pisces. If you get up early you can see three planets. The most brilliant Venus shines at magnitude –4.7. Venus rises around 3:30am and is well up by the time the first blush of twilight starts to color the sky. Venus joined by Jupiter shortly before 6am. Jupiter, at magnitude –1.8, is easy to locate even as the sky brightens. On Friday morning, Mercury and Jupiter have a very close encounter at dawn when the innermost planet catches up to the Jupiter. Find a location with an unobstructed view to the southeast as the planetary pair hovers just seven degrees above the horizon, 45 minutes before sunrise. Mercury, which is enjoying its best apparition of 2018, at magnitude –0.5, is noticeably fainter than Jupiter, but still an easy catch.

This weekend is brightly lit by the full Moon, making deep-sky hunting and comet viewing difficult. However, you can still try to locate Comet 46P/Wirtanen in Auriga. It sits just 1 degree east of zero-magnitude Capella on Sunday evening.

Winter is the best season to appreciate the full Moon as it rides high on the ecliptic, where it’s ideally positioned. The fully lit lunar disk may appear blindingly bright, but there’s no risk of eye damage. Once you adjust to the glare, there’s plenty to see. If you want to look at the full moon comfortably, then perhaps consider using a moon filter. Now try to locate Cassini’s Bright Spot. It lies north of the conspicuous ray crater, Tycho, and appears in a telescope as a small, brilliant patch of whiteness. Named after Cassini, the astronomer who first called attention to it in the 17th century, the spot is one of the brightest features on the lunar disk. Cassini’s Bright Spot is in reality an ordinary, 3-kilometre-wide fresh impact crater with a tiny ray system. After you’ve located the spot, hunt for it again in a few nights later. As the terminator nears, Cassini’s Bright Spot becomes increasingly difficult to find. You’ll need a detailed Moon map to have any chance of locating the little crater. It’s interesting to see how a feature so prominent under one lighting angle can all but disappear when conditions change.

This Sunday marks the 346th. anniversary of the discovery of Saturn’s moon Rhea. Giovanni Cassini discovered Saturn’s moon Rhea on December 23, 1672. Rhea is the fifth major satellite of Saturn, which may be one of the most heavily cratered satellites in the solar system. Its surface appears to be saturated with craters, but long, bright linear features can be seen on the trailing hemisphere and linear ridges can be seen in the leading hemisphere. These ancient features may record changes in Rhea’s shape due to internal heating or cooling. Rhea is 950 miles in diameter. Its largest crater is 190 miles in diameter. Cassini also discovered three more of Saturn’s major moons, Iapetus, Tethys, and Dione.

Skywatch Line for Wednesday, December 19th, and Thursday, December 20th, 2018

This is the Dudley Observatory Skywatch Line for Wednesday, December 19th, and Thursday, December 20th, written by Louis Suarato.

The 90% illuminated, waxing gibbous Moon rises at 2:26 Wednesday afternoon. Look for the Pleiades star cluster 17 degrees to the Moon’s left. Thursday night, a fuller Moon will shine amid the stars of the Hyades, and above and to the right of Taurus’ brightest star, Aldebaran. The bright star to the left of Aldebaran is Capella, the brightest star in Auriga. Comet 46P/Wirtanen can be found 20 degrees to the right of Capella. Mars is making its way from Aquarius into Pisces. While viewing Mars, at the distance of 92 million miles from Earth, think about the extraordinary times we live in, when there are operational robotic explorers, including the most recent occupant, InSight, on its surface. The pre-dawn sky features three planets. Venus is most obvious, but Thursday morning there will be a close conjunction of Mercury and Jupiter. Mercury rises first at 5:40 a.m., followed by Jupiter 10 minutes later. You’ll need a clear view of the southeastern horizon to see the solar system’s smallest and largest planets rise together, 2 degrees apart. Friday morning, the two planets will be less than a degree apart.

On December 20, 1900, astronomer Michel Giacobini discovered a comet that was later to be known as Comet Giacobini-Zinner. This comet became the first to be visited by a spacecraft, when, on September 11, 1985, the International Cometary Explorer (ICE) flew through its tail. Comet Giacobini-Zinner orbits the Sun once every 6 years and 8 months and is the origin of the Draconid Meteor Shower, which occurs every October.

The Albany Area Amateur Astronomers invite you to join them for their monthly meeting at miSci in Schenectady beginning at 7:30 Thursday night. This month’s speaker will be Dr. James Johnson. Dr. Johnson’s topic will be The Future of Human Spaceflight. Dr. Johnson will discuss NASA’s collaboration with American companies that are revolutionizing spaceflight, and the goals of some of the most successful entrepreneurs in history.

Skywatch Line for Monday and Tuesday, December 17th and 18th, 2018

This is the Skywatch Line for Monday and Tuesday, December 17th and 18th.

The Sun sets at 4:22 PM; night falls at 6:05. Dawn begins at 5:38 AM and ends with the Sun rising at 7:21.

The 10-day-old Moon lies high in the southeastern sky at Civil Dusk. In Pisces, it blazes with minus 10th magnitude, appears about 74% lit and is highest at 7:50 PM. The Moon sets at 2:24 AM, Tuesday. Tuesday’s Dusk finds the Moon brighter, fuller and highest at 2:37 PM. The Moon sets at 3:31 AM on Wednesday.

Saturn hangs on in Sagittarius, only 4º above the western horizon. Since it sets at 5:24 PM, now is the time for last looks with an unobstructed horizon. Saturn is nearing conjunction with the Sun in January; 2018 is a rare year with no conjunction with the Sun.

Mars and Neptune co-occupy Aquarius. Mars shines with zero magnitude and appears about 8 arc-seconds in size. It sets at 11:22 PM. Mars acts as a guide to much dimmer and smaller Neptune. Neptune glows with 8th magnitude and is a tiny 2.3 arc-seconds in size. It sets at 11:46 PM. Neptune appears about 6º above Mars as a blue-green dot.

Uranus, in Pisces, is brighter at 5th magnitude and a bit larger. It is best observed at 7:56 PM and sets at 2:38 AM. However, the Moon, on both nights, blazes quite close, hindering observation.

Comet P46/Wirtanen is now visible with binoculars and possibly naked-eye, from dark rural sites. It inhabits Taurus and was closest to the Sun on December 12th. Now, it is nearest Earth, about 7 million miles away, and starts to pull away from our planet. The comet is nearest the star Phi Tauri and between the star and the bright star Zeta Persei. Finder charts are available from astronomical media. The brilliant Moon may be too close for useful observing.

Venus, in Libra, is already well up by Astronomical Dawn. It dazzles with minus 4th magnitude and is about 39% illuminated and 20º high in the East. Mercury, in Scorpius, rises just as Dawn begins. In the rapidly brightening sky, it appears about 70% lit and shines with minus zero magnitude. Jupiter appears about 3º below Mercury after rising at 5:56 AM about 7º high in the East.

NASA recently made an historic announcement. Voyager2 has officially left the Solar System. Launched in 1977 with its twin, Voyager1, they explored the solar system and then charged into the unknown. Voyager1 crossed the boundary in 2012. Voyager2 accomplished that on November 5th this year. This boundary is called the Heliopause. Our Sun constantly emits a wind of atomic particles; this is the same solar wind that occasionally causes the Northern Lights. On November 5th, Voyager’s instruments detected a sudden drop in the solar wind and a coincident rise in Cosmic Rays – the indication for leaving the Sun’s influence.

About one hour after nightfall, the constellation Cygnus appears low in the western sky. Ancient peoples knew the constellation by a variety of names, all relating to birds. Cygnus comes to us from the Romans; “cygnus” is Latin for “swan.” It is named for Cycnus – the Son of Mars. Another name for Cygnus is the “Northern Cross.” Around Christmas time, the constellation sets, standing upright against the western horizon and appearing as a Christian cross. Christians see symbolism of the Cross appearing at Christmas as a reminder of the Crucifixion.

Skywatch Line for Friday, December 14 through Sunday, December 16, 2018

This is Dudley Observatory’s Skywatch Line for Friday, December 14 through Sunday, December 16, written by Sam Salem.

On Friday, the Sun rises at 7:19am and sets at 4:22pm; the waxing crescent Moon rises at 12:07pm and sets at 11:19pm. The first-quarter Moon occurs on Saturday at 6:49am. The waxing crescent Moon and Mars are positioned less than five degrees apart on Friday evening. The two objects will be closest around 11:15pm.

It’s possible to see all five naked-eye planets this week, two at dusk and three at dawn. Mars, glowing at magnitude 0.2, is an easy catch as it transits the meridian at roughly 6pm. You’ll need binoculars and an unobstructed view to catch Saturn, at magnitude 0.5, as it sits low in the southwest during twilight. Saturn hovers just 4 degrees above the horizon 45 minutes after sunset. Venus, gleaming at magnitude –4.8, rises around 4am and is well up before the first hint of twilight. Trailing behind are Mercury and Jupiter. Mercury shines at magnitude –0.4 and is in the midst of its most favorable apparition for 2018. Mercury reaches greatest elongation in the morning sky on Saturday and is well positioned for viewing at dawn. The little planet reaches an altitude of nearly 10 degrees, 45 minutes before sunrise. At that same time, Jupiter, at magnitude –1.7, sits just 3 degrees above the southeast horizon. Jupiter is re-emerging from its November 26 conjunction with the Sun, and climbs slightly higher each morning.

The Geminid meteor shower reaches its peak Friday night. Conditions are good this year. The crescent Moon setting as the shower’s radiant climbs high in the northeast. The best time to look for Geminids is in the predawn hours. That’s when the radiant point is high overhead and the display is expected to be reaching its peak. In a dark country sky free from light pollution, up to 80 Geminids could be seen per hour.

This weekend is prime time for Comet 46P/Wirtanen. In addition to its lovely fly-past of the Pleiades cluster this weekend, the comet drifts closest to Earth, lying only 11.5 million kilometres from us on Sunday. That’s 30 times farther away than the Moon, but good enough to make Wirtanen the 10th closest cometary encounter we’ve had since 1950. Wirtanen appears in the sky as a large, diffuse puffball. The most recent reports indicate that Comet 46P/Wirtanen is glowing at magnitude 5 and can be glimpsed with the naked eye, or more easily in binoculars, under a dark sky. The comet should be brighter this weekend. However, its diffuse nature means it’s likely to suffer from light pollution more than similarly bright comets. Under adverse sky conditions Wirtanen may not stand out as well as its magnitude number suggests. Regardless, this is the finest comet we’ve had in some time, so it’s worth braving the cold and making an effort to get to a good local observing site to take in the show.

Skywatch Line for Wednesday, December 12th, and Thursday, December 13th, 2018

This is the Dudley Observatory Skywatch Line for Wednesday, December 12th, and Thursday, December 13th, written by Louis Suarato.

The 28% illuminated, waxing crescent Moon sets at 9:25 Wednesday night. Mars remains in the sky until the red planet sets at 11:22 p.m. in the constellation Aquarius. :Look for Mars earlier in the day when the International Space Station passes close to the red planet. This will be a bright -3.1 magnitude pass of the ISS over our region. Look toward the west-northwest horizon at 7:33 p.m. to see the ISS begin its trek across the sky. The Space Station sails through Hercules and continues onto Sagitta. The ISS will pass the Pegasus Cluster before sailing by Mars. The Space Station continues toward the southeastern horizon before disappearing into Earth’s shadow.

Comet 46P/Wirtanen is now at 4th to 5th magnitude, and naked eye visible under less light polluted skies. In less than 4 days after perihelion, its closest approach to the Sun, Comet 46P/Wirtanen will be at its nearest to Earth on December 16th. The comet will come as close as 7.1 million miles, or 30 Lunar distances. This “Christmas Comet” as it is being called, may even brighten in magnitude during this time. Orion’s belt and bow point to this comet Wednesday night. At around 9 p.m., look about 54 degrees above the southeastern horizon for this bright comet. You’ll find it to the lower right of the Pleiades star cluster, and 25 degrees to the right of Taurus; brightest star, Aldebaran.

The best meteor shower of the year, the Geminids, peak Thursday night into Friday morning. The Geminids and the Quadrantids are thought to be the only major meteor showers that didn’t originated from comet debris. The origin of the Geminids is the asteroid 3200 Phaethon. This meteor shower can yield as many as 120 meteors per hour. The Constellation Gemini, the radiant of the meteor shower, rises in the east-northeast around 7 p.m.. As the constellation rises, the number of visible meteors should increase. Characteristics of Geminid meteors include being a yellowish hue, which indicates the asteroid debris contains a high concentration of iron. The Moon sets at 10:24 Thursday night, providing good conditions to view these meteors. Clear skies!