Once in a blue moon, this Friday

There’s something everyone does every once in a blue moon. If you take that idiom literally, Friday is the day to do that thing you do occasionally.

Space aficionados will be able to watch the blue moon Friday. The next time this rare sight will be visible will be July 2015.

A blue moon occurs when there is a second full moon in one calendar month. The moon could appear blue because of smoke or volcanic ash particles suspended in the atmosphere.

“The moon will turn full Friday, the second time since its first full appearance Aug 2 this year. The next blue moon will only be seen three years from now, July 2015,” said Science Popularization Association Communicators and Educators (SPACE) in a statement.

The average interval between full moons is about 29.5 days, while the length of an average month is roughly 30.5 days.