Blue Moon Over Washington

©NASA/ Bill Ingalls

Blue Moon Over Washington

A second full moon for the month of July is seen next to the dome of the U.S. Capitol on Friday, July 31, 2015 in Washington.

In recent years, people have been using the name Blue Moon for the second of two full moons in a single calendar month. An older definition of Blue Moon is that it's the third of four full moons in a single season.

Image Credit: NASA/Bill Ingalls Larger image

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