Once in a blue moon there is one on New Year’s Eve. And this year, revelers ringing in 2010 will be treated to the rare sight. But don’t expect it to be blue—the name has nothing to do with the color of our closest celestial neighbor. A blue moon, by definition, is the second full moon occurring in a single month. A full moon was visible on December second, and will appear again just in time for the New Year’s countdown.
And, in case you were wondering, the last blue moon that occurred on New Year’s Eve was nineteen years ago, in 1990. We won’t see another until 2028.