Rare blue moon to appear in sky tonight

A girl is silhouetted against a rising full moon as she ride an attraction at Worlds of Fun amusement park Thursday, July 30, 2015, in Kansas City, Mo. (AP)

A rare lunar event known as a blue moon will be happening tonight.

A blue moon happens when there is a second full moon in any calendar month. Normally there is only one full moon per month, but this year has 13. The last time there was a blue moon was in August 2012, and the next one will be in January 2018.

Despite its name, the moon probably won't appear blue but actually gray and white, similar to what the moon may look like on any other night. A moon that appears to be the color blue -- different from a full moon -- can appear on rare occasions, most often being seen after volcanic eruptions or even during forest fires.

Friday's moon could even appear red, according to NASA.

"Often, when the Moon is hanging low, it looks red for the same reason that sunsets are red," NASA said on their website. "The atmosphere is full of aerosols much smaller than the ones injected by volcanoes. These aerosols scatter blue light, while leaving the red behind."

Take a look outside tonight to see the astronomical event that only occurs "once in a blue moon."

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