Unlike other year-end parties, 2009 will go out with a blue moon, or in other words the “second full moon in a calendar month, something that hasn’t happened on a New Year’s Eve for nearly 20 years, NASA says.” So, be sure to keep your eyes peeled tonight should you take a break from partying.

Full moons used to have 12 names, one for each month, such as “harvest moon,” NASA said. The term “blue moon” referred to the 13th full moon in a year.

[via CNN – image via]