‘Once in a blue moon’ in the sky now

Published: Thursday, July 23, 2015 @ 3:58 PM
Updated: Friday, July 31, 2015 @ 1:06 AM


            Blue Moon (Graphic by StormCenter 7 Chief Meteorologist Eric Elwell)
Blue Moon (Graphic by StormCenter 7 Chief Meteorologist Eric Elwell)

So have you ever told someone that “it only happens once in a blue moon?”

Well, that blue moon is in the sky now. The best time to view the full moon is from 6 to 6:43 a.m. today.

The moon is not actually be blue. And we aren’t talking about the adult beverage either. So what really is a blue moon?

Content Continues Below

There are actually two definitions of a blue moon in astronomy; both are a type of full moon. (If the moon actually looks blue, it’s caused by a rare type of dust in the atmosphere.)

The term “once in a blue moon” means that that something is rare. But just how rare depends on your definition.

In astronomy, a blue moon is a full moon, which doesn’t quite fit in with the months in our calendar. However, there are two different ways of calculating which full moon is a blue moon.

1) blue moon = The third full moon in an astronomical season with 4 full moons (versus the normal 3)

2) blue moon = The second full moon in a month with two full moons.

That being said … the correct, original definition is that a blue moon is the third full moon in an astronomical season with four full moons. A normal year has four astronomical seasons — spring, summer, fall and winter — with three months and normally three full moons each. When one of the astronomical seasons has four full moons, instead of the normal three, the third full moon is called a blue moon.

So now you know! (or are you more confused?)