This year for Christmas day, we get a nearly full Moon and a
terrific alignment with the giant planet Jupiter and the bright star Aldeberan.
They will dominate the night sky from sunset to sunrise, bringing a slowly
changing pattern to bear as they soar high across the Christmas nighttime sky. The
Moon’s gradual eastward motion will be perceptible in this tightly-packed
alignment, rewarding the careful observer with a chance to see the Moon’s
proper motion as it orbits the Earth, moving roughly its own diameter in
distance across the night sky every hour, compared to Jupiter and Aldeberan. If you use binoculars to view the spectacle, you'll get the added bonus of seeing the Hyades star cluster, an open cluster of stars surrounding the star Aldeberan.
I wish you clear skies and nice viewing as we close 2012.
In 2005 I began writing a column for the San Francisco Waldorf School newsletter called "The Urban Astronomer." I started this blog in 2007 as a place to archive my articles and to offer additional insights on the night sky - even if you live in a big city. In 2008 I became an occasional guest on the KFOG Morning Show, and more recently on KALW and KGO. Archived shows are posted on the blog. I conduct private star parties for special events and corporate events. Contact me for details.