Tonight, a vibrant sight will light up the sky in the form of a  "blue" moon, the second full moon in a month. Blue moons are a misnomer, as the moon doesn't usually appear blue.

There's a "blue moon" tonight, but it probably won't look blue. Image 1.

Image: / Karl Tate

The term was used by the Maine Farmers Almanac sometime in the 1800s and refers to the third full moon in a season containing four. It was clarified later by Texas astronomer Donald W. Olson to mean the second full moon in one month. This happens approximately every 2.7 years.

It was introduced to the Morris Dictionary of Word and Phrase Origins in 1528 to describe "a rare event."



 Native American Algonquin language has different names for moons in each month. 

 Tonight's blue moon will rise at approximately 8:30 PM Eastern time in the United States.

 Sometimes, in the presence of volcanic ash and forest fires, the moon does actually appear blue due to the filtration of light.

Cover image: Flickr