SKY GUIDE: This map represents the night sky as it appears over Maine during December. The stars are shown as they appear at 10:30 p.m. early in the month, at 9:30 p.m. at midmonth, and at 8:30 p.m. at month’s end. Jupiter and Saturn are shown at their midmonth positions. To use the map, hold it vertically and turn it so that the direction you are facing is at the bottom. Sky Chart prepared by Seth Lockman
The long, cold nights in the month ahead will be easier to enjoy, because this year there will be more than the usual astronomical highlights for December.
Jupiter in the constellation of Aries the Ram near Taurus is still the brightest evening planet, about 25 times brighter than Saturn, which is located 30 degrees and two constellations to the west in Aquarius. Both of them are getting a little fainter and farther away now each evening as we are leaving them farther behind in space in our faster orbit around the sun. Saturn was at its best back in August and Jupiter reached its best in early November.
You can look for the bluish-green planet Uranus about 10 degrees to the left of Jupiter half way to the Pleiades along the ecliptic. It glows at 5.7 magnitude, a little brighter than usual since it just reached opposition late last month. The limit of visibility for the unaided human eye is 6th magnitude, so you should be able to see it without any binoculars from a dark-sky site.
Venus rises at about 4 a.m. in Virgo. It is nearly four times brighter than Jupiter and fully 100 times brighter than Saturn. The slender waning crescent moon will form a nice conjunction with Spica, the brightest star in Virgo on Dec. 8, and it will be near Venus the next morning. Look for the intriguing earthshine on the crescent moon that morning as our two brightest objects in the night sky are just a few degrees apart. As it moves eastward, Venus will get smaller and fainter and more illuminated by the sun, reaching 78% lit by the end of the year and dropping to minus fourth magnitude in brightness.
The asteroid Vesta will reach 6.4 magnitude on Dec. 19 as it tracks through Orion this month. It is the second-largest asteroid at 330 miles in diameter, which is the distance across Arizona. Vesta reflects 40% of its sunlight, which is four times as much light as our moon reflects, but still only half as much as fresh snow. About 6% of all of the meteorites found on Earth come from Vesta.
An asteroid named 319 Leona will pass directly in front of the bright red supergiant star Betelgeuse in Orion on Dec. 11 at 8:25 pm. 319 Leona is part of the main asteroid belt between Mars and Jupiter, so it is in no danger of running into Earth. We don’t know its exact diameter, but we think it is about 40 miles across, much smaller than Vesta and Ceres. It could either completely cover up Betelgeuse so that this brilliant star will actually go out for about 12 seconds, or it may be a little too small and create something like an annular eclipse.
This very rare event will only be visible over southern Florida from Key West, the Everglades, and up to north of Miami, along with some parts of Mexico, southern Europe, Turkey, and central Asia. However, you can still watch a live feed of it as it is happening. After this, we will be able to determine the exact size and shape of this asteroid.
Comet 62P/Tsuchinshan 1, discovered in 1965, continues to get brighter in Leo. It will reach about 8th magnitude this month and be visible through binoculars or a small telescope. It will pass 6 degrees above Regulus on Dec. 10 and right above the Leo Trio of three small galaxies located about 35 million light years away at the end of the month. Try to get some photographs of it, since it will show up in a time exposure quite well.
Leo now rises around midnight, and the best time to look for this comet will be between Dec. 5-17, when the moon will not interfere.
There are three meteor showers this month, but only one good one, the Geminids. Caused by an asteroid named 3200 Phaethon, which is probably the nucleus of an extinct comet, this is the best shower of the year. It will peak on the night of Dec. 13 into the morning of Dec. 14. You can expect over 100 meteors per hour from a dark sky site, since the moon is new on Dec. 12 and will not interfere.
Then there’s the annual Ursid Meteor shower on the winter solstice (Dec. 21) each year. Caused by Comet 8P/Tuttle, the shower usually produces five to 10 meteors per hour. Since the moon will be waxing gibbous, only five days before it becomes full, you will see even fewer than that.
DECEMBER HIGHLIGHTS
Dec. 3: The waning gibbous moon and Regulus rise in the east just 3 degrees apart this evening.
Dec. 5: Last quarter moon is at 12:49 a.m.
Dec. 8: The moon will pass just 2 degrees above Spica in Virgo this morning.
Dec. 9: The slender waning crescent moon and Venus, our two brightest night time celestial objects, will be just 3 1/2 degrees apart this morning.
Dec. 11: Annie Jump Canon was born on this day in 1863. She was part of the famous Harvard Computers who developed the spectral classification system for all stars.
Dec. 12: New moon is at 6:32 p.m.
Dec. 13: The Geminid meteor shower peaks tonight into Dec. 14.
Dec. 17: The moon passes 2 degrees south of Saturn tonight. The Wright brothers made the first powered flight of an aircraft on this day in 1903 on a beach in Kitty Hawk, North Carolina. The flight only lasted 12 seconds and only went 180 feet, but it proved that it was possible. It only took less than 66 years to get all the way to the moon. We are still progressing rapidly and we will probably get all the way to Mars by 2037.
Dec. 19: First quarter moon is at 1:39 p.m.
Dec. 21: The winter solstice is at 10:27 p.m.
Dec. 22: The Ursid meteor shower peaks tonight. The moon passes 3 degrees north of Jupiter tonight.
Dec. 23: The moon passes 3 degrees north of Uranus tonight.
Dec. 25: Isaac Newton was born in 1642.
Dec. 26: Full moon is at 7:33 p.m. This is also known as the Long Night Moon or the Cold Moon.
Dec. 28: The waning gibbous moon is only 2 degrees from Pollux in Gemini this morning.
Dec. 29: The moon is near the Beehive open star cluster in Cancer this morning.
Dec. 31: The moon is near Regulus in Leo this morning. Jupiter ends its retrograde motion and is stationary in Aries today.
Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.
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