What’s Up in the Sky – December, 2015
A Variety of Offerings in This Month’s Sky
December is not known for clear skies and warm evenings, so it’s a good month to concentrate on some basic observing of easily found objects. Like the Sun.
The winter solstice, which occurs on the date when the Sun rises and sets at its most southern point on the horizon, occurs this year on Monday, December 21 and marks the beginning of winter. You may remember last September when the Sun was shining right in your face as you drove down an east-west road early or late in the day. It is interesting to see how much the location of sunset changes so try to spot one using a westbound road or other landmark as a guide. You may be amazed at the difference.
The Geminid meteor shower is active from December 4 – 17, reaching a maximum on December 14. This is an interesting shower to observe as some of the meteors come in at a very low angle and therefore appear as long, bright streaks.
Lately I have been writing about spectacular observations of the planet Venus encountering the Moon or other planets and this month is no exception, except it’s another before sunrise event, this time on a Monday, no less.
But this one should be worth the effort because Venus will be a beautiful sight right below the crescent Moon. Since sunrise isn’t until about 8 a.m., it should be a spectacular sight as late as 7:30. For veteran observers, try tracking Venus until just past 12:30 p.m. when the planet will disappear behind the sunlit limb of the Moon. A challenging observation.
One of my favorite things to observe this time of year is the constellation Cygnus, the Swan. Also known as the Northern Cross, it’s bright star, Deneb, is part of the Summer Triangle that has been nearly overhead since late summer. This time of year, Cygnus sets a few hours after sunset and, if viewed as a swan, is diving into the western horizon. But if viewed as a cross, it stands straight up on the horizon and can be seen as one symbol of the Holiday Season. Regardless of your interpretation, it is a beautiful sight.
If you look toward the west, you see the constellations of summer and toward the east, the coming constellations of winter, but directly above you can find a constellation that points to another of my favorite objects.
Face south and then look straight up. A little beyond overhead you should see the “W” – shaped constellation, Cassiopeia. Using the right hand “point” of the W, follow it down to just about overhead and look for a fuzzy blob (binoculars help a lot). This is M31, the Andromeda galaxy. This is the only object in the sky visible to the naked eye that is not part of our own Milky Way galaxy and, at over two million light years, is the most distant object you can observe without the aid of a telescope.
All in all, it’s a good month for what’s up in the sky.
This month in history:
Dec. 3: Pioneer 10 spacecraft makes closest approach to Jupiter – 1973
Dec. 11: First auction of Soviet space hardware and artifacts – 1993
Dec. 14: Gene Cernan, Apollo 17 astronaut, is last human to walk on Moon – 1972
Dec. 14: Tycho Brahe born – 1546
Dec. 24: Apollo 8 astronauts give us inspirational moment from lunar orbit – 1968
Dec. 25: Isaac Newton born – 1642