Dec 02

What’s Up in the Sky

What’s Up in the Sky – December, 2018

Bright Stars Make Their Way Into December’s Sky

I was recently in a local Meijer store admiring a very nice seasonal display depicting a winter nighttime scene complete with snowy hills and pine trees, a horse-drawn sleigh, reindeer, and a dark, starry sky. But what really got my attention was the comet in the sky. It was a big comet, spanning a good portion of the sky, and, to the artist’s credit, it was a pretty good rendition of a comet -closely resembling 1998’s comet Hale-Bopp.

It reminded me that the sky is full of beacons and spotlights, patterns and stories, many of which have religious connections, with the Star of Bethlehem and the crescent Moon being two examples. I have written before about the traditions of the season and their relationships to celestial objects and events, but this year I would like to focus on the stars and constellations that are visible and offer some lesser-known facts and tidbits about them.

Many readers are familiar with the Summer Triangle which consists of the stars Vega, Deneb, and Altair, which are in the constellations Lyra, Cygnus, and Aquila, respectively. By now, however, these constellations are no longer high overhead, but are now setting in the west as the evenings get darker. Look for the Northern Cross, standing upright near the western horizon an hour or so after sunset.

In the opposite direction are the constellations of winter that will dominate the southern sky in the coming months. These include Orion, Canis Major and Minor, Gemini, Auriga, and Taurus, which contain the bright stars Rigel, Sirius, Procyon, Pollux, Capella, and Aldebaran, respectively. The group is often referred to as the Winter Hexagon. One interesting feature of this group of stars is that, other than Rigel, they are all 65 or fewer light-years away. In fact, going clockwise from Sirius, the distances are 8 light-years, 11 ly (Procyon), 34 ly (Pollux), 42 ly (Capella), and 65 ly (Aldebaran).

Turning your attention straight up you will also find much to enjoy. Almost directly overhead lies the constellation Andromeda, home of M31, the Andromeda galaxy. The constellation Andromeda is not very prominent so I usually use other constellations as guideposts. One side of the “W” shaped Cassiopeia can be viewed as an arrow pointing at the constellation, for example. Consult any sky or star chart for a more detailed description. Or just set up a warm sleeping bag and scan overhead with binoculars. You will know when you have found M31. If you are under dark skies, in fact, it can be seen with the naked eye. It is the only naked eye object in our sky that is not a member of our own Milky Way galaxy. The stars in our galaxy make up everything else 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. 20: Founding of Mt. Wilson Solar Observatory – 1904
Dec. 24: Apollo 8 astronauts give us inspirational moment from lunar orbit – 1968
Dec. 25: Isaac Newton born – 1642