A "supermoon" rises above Glastonbury Tor on Sunday, August 10, in Somerset, England. The phenomenon occurs when the moon becomes full on the same day as its perigee -- the point in the moon's orbit when it is closest to Earth. It is the second one of the summer. According to NASA, the moon appears 30% brighter and 14% bigger than usual at this time. Another supermoon will appear September 9.