December 2013 astronomy events

¡SkyCaramba! Weekly astronomy blog for the week ending November 30, 2013

The moon is just below Saturn in the middle of Libra at the start of December 2013. Below the moon is Mercury. Mars is next to a start called Zavijava. All three are in the morning sky. Mercury is heading eastward. So is Saturn. You’ll quickly lose Mercury in the dawn, but for most of the month the ringed planet will keep heading toward the middle of Libra. The moon breezes by again on the 28th. That’s about the time Mercury has moved to the other side of the sun.

Meanwhile, Mars is also heading east. Around the middle of the month, it’s close to a star called Zaniah. After a visit by the moon on the 25th, Mars heads for rendezvous with Porrima by the 28th.

If you didn’t get to see Comet C/2012 S1 (ISON) in November, you may get another chance in December. It will be next to a star named Yed Prior on the morning of the 6th. Staying between constellations the first half of December, the comet will go almost on the line between the Serpent and Ophiuchus and then between the Serpent’s head and Hercules. Then it’s on toward Crater and places further north until it disappears from view.

As is explained often by astronomers, comets are hard to predict. Comet ISON may stay fairly bright after the sun heats it up in late November and the solar wind knocks lots of its particles loose. But it’s moving away from the sun in December. Less action like that should make it dimmer. Except it’s also getting closer to Earth. It will be closest to us on the 26th. We’ll just have to wait and see.

In the evening sky, Venus is ending its reign as the brightest object in the southwest after sunset. After a close call with the moon on the 5th, Venus will soon set noticeably sooner after sunset each evening.

Jupiter is almost an all night object, rising in Gemini and coming close to the star Wasat on the 9th. The two are just 0.25° apart. Jupiter will be a little west of the star when the moon is in the legs of the twin Pollux on the 18th. Jupiter will keep heading west and stay in Gemini for a few months.

The Geminids meteor shower should peak around the 13th and 14th. This sometimes colorful shower is what happens when Earth passes through the remnants of old comet trails. The little rock chunks that cause the Geminids came from a comet that’s not a comet anymore. It’s just an asteroid orbiting the sun.

You may get another meteor shower peaking around the 21st. That would be the Ursids. They aren’t one of the legendary meteor showers. Their last two big peaks were in 1945 and 1986. But this northern hemisphere shower may peak again this year, based on one astronomer’s analysis of the parent comet’s orbit.

Southern solstice is on the 21st. The nights will get a little shorter and the days a little longer a few days after that.

That should get you started for December. ¡SkyCaramba!