Since the moonâ€™s orbit is elliptical, one side (perigee) is about 30,000 miles closer to Earth than the other (apogee). The word syzygy, in addition to being useful in word games, is the scientific name for when the Earth, sun, and moon line up as the moon orbits Earth. When perigee-syzygy of the Earth-moon-sun system occurs and the moon is on the opposite side of the Earth from the sun, we get a perigee moon or more commonly, a supermoon!
This coincidence happens three times in 2016. On October 16 and December 14, the moon becomes full on the same day as perigee. On November 14, it becomes full within about two hours of perigeeâ€”arguably making it an extra-super moon.
The full moon of November 14 is not only the closest full moon of 2016 but also the closest full moon to date in the 21st century. The full moon wonâ€™t come this close to Earth again until November 25, 2034.