A rare astronomical event will take place tonight (Monday, August 19th), where a full moon will simultaneously be a supermoon and a blue moon, creating a "super blue moon." This alignment occurs when the moon is both closest to Earth in its orbit and the third full moon in a season with four full moons. Definitions of what constitutes a supermoon or blue moon vary, but this event is particularly uncommon, with the next similar occurrence likely not happening until January 2037.