December Skies

Jon Spargo, New Mexico Tech Astronomy Club

This month our planetary parade features more than just a close encounter with the Moon and a planet.

Both the Moon and Mars reach what it called “opposition” during the evening of 7-8 December. In this case, Mars will be at its furthest from the Sun and the Moon its furthest from the Earth. This will result in the Moon passing in front of (occulting) Mars. The fun will begin just after sunset on the 7th. While the Moon will be bright, so will Mars be bright as it will shine at magnitude -1.8. It will be a treat to watch the Moon slowly cover up Mars. Here in the Mountain Time Zone the fun will begin not long after sunset. For those with good binoculars or a small to medium size telescope, zero in on the disappearance of Mars behind the limb of the Moon. Unlike stars, which tend to “wink” out when they pass behind the Moon, Mars will be fully visible for a bit as its disk is covered by the advancing Moon.

Having passed conjunction with the Sun, both Mercury and Venus now appear in the early evening just after sunset. Both will be found, separated by only a few degrees, just above the southwestern horizon beginning about 20 minutes after sunset. A good pair of binoculars will help in spotting this planetary duo in the afterglow of sunset.

December also brings us another meteor shower, the Geminids. Look to the east on the evening of the 13th-14th as soon as it gets dark. This will be the best time to look for meteors as the waning last quarter Moon will rise in the east about two hours later. The shower should still be active on the following evening, the 14th, with the added benefit of the Moon rising about one hour later. Under good conditions, the Geminids have been known to produce 100 meteors per hour.

The Moon will be full on the 8th, last quarter on the 16th, new on the 23rd, and first quarter on the 30th. Looking west-southwest on the 1st, around 11 p.m., the waxing gibbous Moon will be just to the left of the giant planet Jupiter. Looking east-northeast on the 7th, about an hour after sunset, the nearly full Moon will be quite near Mars. Later in the evening, the Moon will occult, and pass in front of Mars. (See above.) Looking to the southwest on the 24th and 25th, about 20 minutes after sunset, the new crescent Moon will first be found just above the horizon and left of both Mercury and Venus. The next evening, at about the same time, the crescent Moon will be below and to the right of Saturn. Looking high in the southwest on the evening of the 29th, the first quarter Moon will be found about 6 ½ degrees above Jupiter.

The 21st brings to the northern hemisphere the longest night of the year, as the winter solstice begins at 2:48 p.m. MST.

There will not be a first Saturday star party at the Etscorn Campus Observatory this month.

Clear Skies!

Jon Spargo

New Mexico Tech

Astronomy Club