And you’ll have to wait almost another 20 to see the next one.

However, there’s some controversy as to what exactly a blue moon is.

A blue moon is rare, but even more rare for one to fall on New Year’s Eve. The last time that happened was in 1990. The next won’t be until 2028. But what exactly is a blue moon?

However, Missouri S & T physics professor John Schmitt says that’s not entirely accurate.

While it’s always been thought that a blue moon was the second full moon in any given month, researchers now believe it’s an extra full moon in any given season. That means there could be a blue moon that is the first and only in a month. Either way, it’s still a rare occurrence.

Whichever is correct is still being debated, but one thing’s for sure, a true blue moon … when the moon actually looks blue … comes from dust particulates or pollution in the atmosphere.

The next regular blue moon we see in the night sky will be in November, and then again in 2012 … there won’t be one next year.

Schmitt urges those interested to visit the research, debate and calendar online at Sky and Telescope Magazine, and here.

Audio report by Jessica Machetta

Interview with Professor Schmitt (6 min)