Blue moon shines on New Year's Eve

Blue moon over Kentucky?

If there is a break in the winter clouds, revelers heading out to say goodbye to 2009 should see a blue moon.

It will be the first New Year's Eve blue moon since 1990.

Look for a round object in the sky that is, uh, moon-colored.

Blue moons, celebrated in songs and legends (think Blue Moon, by Rodgers and Hart; and Blue Moon of Kentucky by Bill Monroe) aren't really blue.

In its traditional meaning, a blue moon is — for very complicated reasons — the third of four full moons in a season. In recent decades, it's come to be considered the second full moon in a month. Because a lunar cycle is 291/2 days, and most months are 30 or 31 days long, that happens every couple of years.

Both definitions reflect rarity. Something that happens "once in a blue moon" doesn't happen very often. Even rarer is a blue moon on the last night of the year.

Enjoy it if you can see it. The New Year's Eve forecast calls for cloudy skies with a chance of snow or flurries.