A supermoon is a full moon (or sometimes a new moon) that occurs when the Moon is at or near its closest point to Earth in its elliptical orbit, called perigee. This proximity makes the Moon appear slightly larger and brighter than usual when viewed from Earth. Typically, a supermoon can appear up to about 14% bigger and 30% brighter compared to when the Moon is at its farthest point, or apogee
. The term "supermoon" was coined by astrologer Richard Nolle in 1979 and is not an official astronomical term, but it generally refers to a full moon that comes within about 90% of its closest approach to Earth during its orbit
. The technical astronomical term for this event is "perigee-syzygy," where syzygy means the alignment of the Earth, Moon, and Sun during a full or new moon
. Supermoons occur several times a year, usually consecutively, but they are not dramatically larger to the naked eye, and the difference is often subtle. The Moon's elliptical orbit causes its distance from Earth to vary between roughly 363,300 km (perigee) and 405,500 km (apogee), which explains the size and brightness changes during supermoons
. In summary, a supermoon is a full moon that appears larger and brighter because it coincides with the Moon's closest approach to Earth in its orbit.
