The last full moon of the year—also known as the "Cold Moon"—on Thursday night fired up the skies across America. A supermoon occurs when a full moon coincides with the moon’s closest approach to Earth in its orbit, a point known as perigee, making it appear slightly bigger and brighter than usual. NASA points out that the term supermoon is not an official astronomical term, but describes the event as "a full Moon that comes within at least 90 percent of perigee." Also known as the "Long Night