Taurus Treats, Two Evening Comets, the Moon Meets Planets at Dawn and Dusk, and Mars Nudges Neptune!

Bright Comet Update

Last week we alerted everyone to an evening comet to look for. Here’s an update on how to see Comet 46P/Wirtanen this week and what to expect.

Comet 46P/Wirtanen will brighten until mid-December, when it will be closest to both Earth and the sun. It’s getting bright enough to see without binoculars if you are away from artificial lights, especially when the moon is out of the evening sky as it will be this week. Binoculars will be your best option to see it. Look for a green, fuzzy blob surrounding a bright point of light. If Wirtanen grows a tail, the tail will extend east (to the left).

You can begin to look for the comet as soon as it’s dark. The comet will then climb to its highest point, in the lower half of the southern sky, at around 10 pm local time. Then it will set in the west at about 3 am local time.

(Above: Christopher Go of Cebu, Philippines took this image of Comet 46P/Wirtanen on December 2, 2018 using a Nikon camera on a tracking mount.)

The orbit of this comet is carrying it upwards through the plane of the solar system from below. This week, the comet will continue to drift north, moving it higher in the sky for observers in mid-northern latitudes. Tonight (Sunday) Comet Wirtanen will be located in eastern Cetus (the Whale) and about 2.5 finger widths below that constellation’s modestly bright star Sadr al Kaitos. Because the comet is rapidly moving to the left and upwards, on Monday night it will pass only half a finger’s width below Sadr al Kaitos by midnight EST. On Tuesday at 6 pm EST, the comet will sit one finger’s width to the left of that star.

On Thursday evening, the comet will pass extremely close to another star that’s visible to unaided eyes — Azha, in the constellation of Eridanus (the River). You’ll be able to centre that star in the field of view of a small telescope at low magnification and see the comet in the same field of view. On next Sunday night the comet will pass a palm’s width below the medium-bright star Menkar in Cetus. (Cetus has an irregular boundary with Eridanus!)

(Above: The path of Comet 46P/Wirtanen during the week of December 2–9, 2018, as shown at 6 pm local time. Each yellow circle represents 6 hours of time.)

The Moon and Planets

The moon will spend most of this week swinging sunward towards Friday morning’s New Moon phase. Early in the week, the waning crescent moon will rise in the wee hours and linger into the daytime morning sky. On Monday morning before dawn, in the southeastern sky, its very slim waning crescent will be visible a palm’s width above the very bright planet Venus.

You can use the moon to find Venus in the daytime on Monday, too! Just search to the moon’s lower left for a very bright pinpoint of light! Independent of the moon’s monthly visits near her, Venus will be situated in the morning sky for quite a while. The bright white star Spica in Virgo (the Maiden) will be positioned off to the right of Venus. Viewed through a telescope, Venus will exhibit a slim crescent phase similar to the moon’s. Venus is also reaching its maximum brightness for the year now — a stunning magnitude of -4.87! (The more negative the magnitude value is, the brighter the object is. A full moon’s magnitude is -12.4 and the sun’s is -26.8! Positive magnitudes are dim. The faintest stars you can see in light polluted skies are about magnitude +4. The Big Dipper’s stars are about +2.)

(Above: The old crescent moon will land above Venus on the morning of Monday, December 3, as shown here for 5 am local time.)

Low in the eastern pre-dawn sky on Tuesday, the old crescent moon will sit less than 2 finger widths to the lower right of the dwarf planet Ceres. Located in the main asteroid belt and 3.4 Astronomical Units (One AU is the mean Earth-sun separation.) from Earth, magnitude 8.85 Ceres will be visible in binoculars and small telescopes.

When Mercury rises from the east-southeastern horizon at approximately 6 a.m. local time on Wednesday, it will be sitting less than a palm’s width below (east of) the very slender crescent moon. When viewed in a telescope, Mercury will exhibit a similar looking crescent phase. The best time to see Mercury this week will occur before 7 a.m. local time.

The moon will vanish from view while it passes through the sky where the sun is on Friday at 2:20 am local time, but the new moon will slide far enough east of the sun to re-appear for a short time, low in the western sky, on Friday after sunset. For a short period after sunset on Saturday, the young crescent moon will be visible close to Saturn in the southwestern sky. For observers in the Eastern Time zone, Saturn and the moon will set while the moon is still 4 finger widths to the lower right of Saturn. But the moon’s orbital motion will be carrying it towards the ringed planet. The farther west on Earth you are, the closer the moon will get to Saturn before the duo sets.

Mars will remain visible, even while it shrinks in size and brightness, until next May. This week, the reddish planet will shine as the brightest object in the lower part of the southern evening sky among the stars of Aquarius (the Water-Bearer). It will set in the west just before midnight local time. Mars’ orbital motion has been carrying it eastward, directly towards distant Neptune, setting up a very cosy meeting of the red and blue planets this week — one of the year’s best telescope sights. Here are more details.

Tonight, Mars will be located a three finger widths to the lower right (west) of Neptune. On Thursday evening, Mars will be situated less than 0.5 degrees west (a half finger-width to the lower right) of Neptune. On Friday evening, Mars will move to land 0.25 degrees east (to the upper left) of Mars. On both nights, the pair of planets will appear together in the field of view of a telescope at medium to high magnification. Mars is 30 times farther away than Neptune! Minimum separation, with Mars positioned only 2 arc-minutes above Neptune will occur at 14:05 GMT on December 7 — a sight visible in Western Europe, Asia, and Australia. Note: Your telescope may flip and/or mirror the view.

(Above: Mars will be located a three finger widths to the lower right (west) of Neptune this week)

Blue-green Uranus (“YOU-ran-us”) is in the southeastern evening sky. It’s still close to its peak brightness (magnitude 5.7) and size for this year. You can see Uranus without optical aid under very dark skies, but binoculars and telescopes will make seeing it easier. Look for Uranus about 1.5 finger widths to the upper left (east) of the modestly bright star Torcular (Omega Piscium). That star sits a generous palm’s width above the “V” where the two starry cords of Pisces (the Fishes) meet. By late evening, Uranus will be high enough in the southeastern sky to see it clearly.

Don’t forget to look for the major main belt asteroid Juno. It recently reached opposition, causing it to appear at its brightest and largest for this year. This week, the magnitude 7.6 object will be visible in binoculars and small telescopes all night long after it rises in the east at 5:30 pm local time. Juno will be positioned about 2.5 fist diameters from the bright stars Aldebaran in Taurus (the Bull) and Rigel in Orion (the Hunter). Juno will reach its highest position, about halfway up the southern sky, just after 11 pm local time.

Treats in Taurus

Every year in early December, the distinctive constellation of Taurus (the Bull) returns to our evening skies, rising as darkness falls and crossing the sky through the night. It’s one of a handful of distinctive winter constellations that are easy to recognize with unaided eyes. It contains many wonderful objects to observe in small or large telescopes — from spectacular star clusters to a supernova remnant and more. Let’s talk about some of its treats you’ll spy during a winter stroll, and others that make setting up your telescope on a cold winter evening worth your while.

The constellation of Taurus is located on the ecliptic, just north of the celestial equator, making it visible almost globally. With the dim constellations of Cetus (the Whale), Pisces (the Fishes), and Aquarius (the Water-Bearer) lying just to the west of it (on the right), it makes quite an entrance as the late autumn nights lengthen. Taurus is the first in a parade of much brighter and better-known constellations such as Orion (the Hunter), Auriga (the Charioteer), and Gemini (the Twins). Being on Taurus’ eastern side, they rise later in the evening. To the north sits Perseus (the Hero) and below Taurus is the dim and winding constellation Eridanus (the River).

(Taurus is one of a handful of distinctive winter constellations that are easy to recognize with unaided eyes.)

Taurus is dominated by several elements that combine to make the bull. A large triangular arrangement of stars form the bull’s face, with the bright reddish star Aldebaran sitting at the southeastern (lower left) vertex, marking his baleful eye. He’s literally seeing red! Two bright stars sitting 1.5 fist diameters to the lower left (east) mark the tips of his horns. Well above the face, the little Pleiades cluster marks his hunched shoulders — and to the east, a handful of less prominent stars form his chest and forelegs. The rest of him is missing. When he rises in the east, he is tilted sideways, horns down and legs extended — as if he’s charging the twins of Gemini. His doesn’t straighten up until after midnight when he enters the western half of the sky.

This week, Taurus rises at about 5 pm local time and climbs high into the southern sky around midnight, before descending westward to set around 7 am. To find the bull, continue the line formed by Orion’s belt westwards (upwards in early evening, or to the right later on) about two outstretched fist diameters (or 20°) until you reach bright Aldebaran. If Orion hasn’t risen yet, you can look high in the east for the little cluster of blue stars called the Pleiades. Taurus is about 12° below it.

Taurus’ triangular face is actually one of the nearest open star clusters to us. It’s only about 150 light years away. It’s called The Hyades, named for the five daughters of Atlas in Greek mythology. It actually contains several hundred stars, with a half-dozen or so readily seen under moonless suburban skies. It’s a lovely target to view in binoculars. By the way, Aldebaran is not part of the cluster. It is less than half as far away!

One of my favorite objects in Taurus sits about one and a half fist widths above the bull’s face. It is the beautiful star cluster known as The Pleiades, or the Seven Sisters. It’s also designated Messier 45 (or M45), part of Charles Messier’s famous list of comet-like objects. The Pleiades is made up of the young, hot blue stars Asterope (“A-STER-oh-pee”), Merope, Electra, Maia, Taygeta, Celaeno, and Alcyone that are indeed related — born of the same primordial gas cloud. In Greek mythology, they were the daughters of Atlas, and half sisters of the Hyades. To the naked eye, only six of the sister stars are usually seen, with their parent stars Atlas and Plione huddled together at the east end of the grouping. Under magnification, hundreds of stars appear.

The Pleiades cluster is about 450 light years away, and makes a wonderful target in binoculars or a low magnification telescope, where many more siblings are revealed! A large telescope under dark skies will also reveal blue nebulosity around the stars — this is reflected light from unrelated gas that the stars are passing through. Galileo was among the first to observe the cluster in a telescope. In 1610, he published a sketch made at the eyepiece. Not surprisingly, many cultures, including Aztec, Maori, Sioux, Hindu, and more, have noted this object and developed stories around it. In Japan, it is called Suburu, and forms the logo of the eponymous car maker. Due to its shape and diminutive size, some people mistake the Pleiades for the Little Dipper.

The supernova remnant called the Crab Nebula (or Messier 1) sits a finger’s width above the bull’s lower horn star, Tianguan. You need a very large telescope to see the remnant as a dim, fuzzy patch — but on July 4, 1054 AD Chinese astronomers recorded that the star that exploded to create the Crab Nebula shone bright enough to see it in the daytime for three weeks! Then it faded to become the brightest night time star for a few months. The object is about 6,500 light-years from the sun.

One more treat — a very red, magnitude 4.3 star named The Ruby Star (or 119 Tauri) sits 2.7 finger widths to the right of Tianguan. It’s a variable star that pulsates every 165 days. There are even more sights to see in Taurus. And the outer rim of the Milky Way passes just beyond the horn tips, so this area will reward scanning with binoculars or telescope, too.

Astronomy Skylights for the week of December 2nd, 2018 by Chris Vaughan.

Keep looking up, and enjoy the sky when you do. I love questions and requests — so, send me some!

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