What’s Up This Month – December 2008

For those of us in the northern hemisphere, the sky darkens early and deeply this time of year. We can get a full night of observing in and still get to sleep at a decent time. But don’t envy us, you in the southern hemisphere, because it’s getting cold here and the long-term forecast is for a tough winter. I’ve never enjoyed Christmas in the southern summer before. But after forty-four Canadian winters, I’m starting to think it might be nice to give one a try.

Celestial Events This Month

Two events of note this month, both occultations in which the moon passes in front of a more distant object.

• Moon Occults Venus. Tonight, for those of you in Western Europe, the Moon will pass in front of Venus in late afternoon or early evening (December 1). Venus will disappear behind the shaded part of the Moon’s face, then reappear from the brightly-lit crescent. You’ll need no optics to see this, but a pair of binoculars or telescope will improve the view.

• Moon Occults Pleiades. On the night of December 10-11, the Moon gets in the way again. Those of us in North America will see a nearly-full Moon occult the Pleiades around 2:30 a.m. Eastern and 10:30 p.m. Pacific. (The 4-hour difference is due to the different viewing angles between the east and west coasts, not just the standard 3-hour time difference). A small telescope will give you a fine view.

You can also see…

• Geminid meteor shower. This is one of the finest meteor showers of the year, surpassed only by the Perseids. The shower peaks on the night of December 13-14. The radiant (the point in the sky from which most meteors appear to originate) is just north of the bright star Castor in Gemini. In a good year, you can see 100-150 meteors an hour. But this will not be a good year, alas: the full Moon this month obscures all but the brightest meteors.

And Winter Solstice occurs at 12:04 UTC on December 21. This is the shortest/longest day of the year in the northern/southern hemisphere and marks the beginning of winter/summer.

Moon and Planets

• A crescent moon makes a fine spectacle with Jupiter and Venus on December 1-2. As I mention above, Europeans can see the Moon pass in front of Venus later today.

The southwestern sky on Dec. 1 2008 (click to enlarge).

• Saturn shines brightly beneath the hindquarters of Leo this month. The planet is at quadrature on the 13th, lying 90 degrees west of the Sun. Saturn’s rings are almost edge-on right now, so you’ll get a sublime view of this beautiful planet at moderate to high magnification.

• Neptune plays tag with Venus on December 27th. The distant giant planet is just 1.5 degree northwest of Venus, itself just northwest of delta Capricorni.

• After sunset on December 28th, Mercury lies just below Jupiter, and a thin crescent Moon lies below both in the southwestern sky. Binoculars give the best view.

• The Moon comes around again at month’s end, hovering 4 degrees above Venus on the last day of the year.

Sights To See (north and south)

If you brave the cold and wrestle your telescope into the backyard, try hopping through the open star clusters of Cassiopeia. This rich region has at least half a dozen clusters primed for viewing this month. If you have dark sky, try NGC 7789 which lies just southwest of beta Cass. It has many faint stars which are hard to see in light-polluted skies. And don’t miss NGC 457, also known as the “E.T. Cluster” after the famous alien in Steven Spielberg’s classic movie. Take a look at this cluster through a telescope, and you’ll see how it got its name.

Open star clusters in Cass (click to enlarge).

And for you southerners lingering on the beach in early summer as Orion performs a celestial cartwheel high overhead, you have the wondrous Magellanic Clouds to enjoy along with two beautiful star-forming regions: the Orion Nebula and the Eta Carina Nebula. No winter jackets required.

Have a fine month. Get outside and look up!

As the year grows old
Jupiter delights Venus
Silent snowflakes fall.