December 2015 astronomy events

Mercury is an evening object this month. Best viewing is close to the equator. A thin crescent moon passes by the planet on the 12th and 13th. Mercury is at greatest elongation on the 29th. It will be 19.7° from the sun in the evening sky.

Jupiter, Mars, and Venus continue to dominate the morning sky. The way they appear to be pulling apart and rise earlier each morning, you could be forgiven for not noticing that they are all moving eastward. So they appear to be going down while the stars behind them go up from morning to morning.

Jupiter moves slowest of the three. It is above Virgo all month. Mars starts the month just north (or left) of the star Porrima, while Venus is below and left of Spica. The moon passes by Jupiter on the 4th, Mars on the 5th and 6th, and Venus on the 7th.

By the 22nd, Mars is left of Spica and Venus is smack dab in the middle of the diamond of Libra. Venus, the fastest of these three planets, leaves the diamond on the 26th.

It’s doubtful you’ll see the mon next to Saturn on the morning of the 10th. The ringed planet is in Scorpio’s claws. It will become easier to see left of Antares as the month goes on. Venus will be drawing close to the planet as the month ends. But the rendezvous won’t happen until January 9. Watch Saturn and Venus until then. A crescent moon will pass by them a few days before they are at their closest.

The moon is new on December 11th. That’s good for the Geminid meteor shower peak on the 13th and 14th. A still very thin crescent moon will set in early evening to leave the skies dark most of the night.

A waxing gibbous moon interferes with the Ursids shower when it peaks on the 21st and 22nd though. On a dark night, you might see five to ten Ursid meteors per hour. You should expect to catch only a few really bright ones this year.

This year’s southern solstice is on December 22nd at 04:48 UT.

The moon is full on the 25th.

There are a few lunar occultations to note this month. The moon passes in front of Mars on the 6th. It will be visible at about 02:42 UT from central Africa. Venus is occulted on the 7th for viewers in North America who can find the planet in the daytime. That will be at about 16:55 UT. And Aldebaran will be hidden on the 23rd for viewers in Europe and central Asia at about 19:32 UT.