This is the second full moon to shine down on us in the month of December. Blue moons are properly said to occur when there are 4 full moons in a season. By this measure, the next blue moon is November 21st, 2010. However, it is also commonplace to call the second moon in a calendar month a blue moon. This definition of the blue moon is a relatively modern one. The earliest record of this usage dates back to 1946, when it appeared in an issue of Sky & Telescope magazine.
So this is it, the last full moon of 2009, a blue moon seeing in 2010. I hope it portends well for the upcoming year. I hope you have a safe and enjoyable celebration and a year that brings you much joy. Happy New Year!