Tonight's Blue Moon
You've heard the phrase, "once in a blue moon"? The phrase often refers to something unusual or rare. A "blue moon" doesn't happen every day—or even every year. As the infographic below from Space.com explains, the name of this event has nothing, really, to do with color.
For more information about the history of the "blue moon," see "Last 'blue moon' until 2015 lights up night sky tonight."