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In the Sky This Month

The smallest and largest of the Sun’s major planets will stage a relatively rare encounter this month as they pass each other in the dawn twilight. Jupiter should be easy to see, but Mercury could take some work. The great Winter Circle climbs higher each night, and is in good view by 8 p.m. by month’s end. It consists of seven bright stars encircling orange Betelgeuse, the shoulder of Orion.

December 13: Comet Wirtanen

Comet Wirtanen is streaking across Taurus, which is in the east at nightfall. It will pass between the bull’s “eye” — the star Aldebaran — and shoulder — the Pleiades star cluster. Under dark skies, the comet may be bright enough to see with the eye alone.

December 14: Moon and Mars

Mars is in great view tonight. The Red Planet looks like a bright orange star just above the Moon as night falls. It will stand farther to the right of the Moon tomorrow evening.

December 15: Auriga

Auriga is low in the east-northeast as night falls and climbs high across the sky later. It is marked by a pentagon of stars. It’s easy to pick out thanks to the brightest member of that figure, Capella, which is one of the brightest stars in the night sky.

December 16: Messier 37

Messier 37, a 500 million-year-old star cluster, climbs high overhead during the night. It’s not quite visible to the unaided eye, but it’s a fairly easy target for binoculars. It probably is about 5,000 light-years away, and contains about 500 known stars.

December 17: Saturnalia

Today is the beginning of Saturnalia, an ancient Roman festival. The early Christian church may have adopted December 25 as the date for Christmas in part to counteract the appeal of Saturnalia and other festivals.

December 18: Zodiac

As twilight fades away, the zodiac arcs high across the southern sky. It is a trail of constellations with one thing in common: The Sun’s path across the sky traverses their borders, so the Sun passes through each of those constellations during the year.

December 19: Jupiter and Mercury

Jupiter and Mercury, the largest and smallest of the solar system’s major planets, are getting together in the dawn sky. For the next few days, they will be separated by less than the width of your finger held at arm’s length. Jupiter is the brighter of the two.

Current moon phase

New MoonNew Dec. 7, 1:20 am

First QuarterFirst Dec. 15, 5:49 am

Full MoonFull Dec. 22, 11:49 am

Last quarterLast Dec. 29, 3:34 am

Times are U.S. Central Time.

Apogee Dec. 12

Perigee Dec. 24

The full Moon of December is known as the Long Night Moon or Moon Before Yule Moon.