Ever heard the phrase, “Once in a blue moon?”
A blue moon is the second full moon in a calendar month, and as the saying implies, it’s a pretty rare occurrence.
Tonight, however, skywatchers are in luck.
Aug. 31 marks the second full moon this month, following a full moon on Aug. 1 and 2, NASA reports.
The moon completes its orbit around the earth every 29.5 days, so every now and again, two full moons can make an appearance within a typical 30- or 31-day month. Tonight's will be the last until July 2015.
So does the term have anything to do with the moon’s color?
“Most blue moons look pale gray and white, indistinguishable from any other moon you've ever seen. Squeezing a second full moon into a calendar month doesn't change the physical properties of the moon itself, so its color remains the same,” NASA reports.
The rare lunar occurrence is not without note in pop culture.
"In song and literature, blue moons have long symbolized lost love and melancholy," NASA reports. "Elvis set the standard for lunar heartbreak in his 1956 pop hit 'Blue Moon.'"
Tonight's full moon doesn't have to be hearbreaking, however. If you're looking for a fun way to celebrate while skywatching, check out the Blue Moon Party at Washington, DC’s Penn Social, which is offering drafts of Blue Moon Belgian beer for $4 between 7 and 9 p.m.
Penn Social is located at 801 E Street in Northwest Washington.
Will you watch the blue moon tonight? Do you know of more blue moon specials or parties around town? Tell us in the comments.