Once in a blue moon there is one on New Year’s Eve. Revelers ringing in 2010 will be treated to a so-called blue moon. According to popular definition, a blue moon is the second full moon in a month. But don’t expect it to be blue — the name has nothing to do with the color of our closest celestial neighbor. A full moon occurred on Dec. 2. It will appear again on Thursday in time for the New Year’s countdown. “If you’re in Times Square, you’ll see the full moon right above you. It’s going to be that brilliant,” said Jack Horkheimer, director emeritus of the Miami Space Transit Planetarium and host of a weekly astronomy TV show.