A supermoon is the coincidence of a full moon or a New moon with the closest approach the Moonmakes to the Earth on its elliptical orbit, resulting in the largest apparent size of the lunar disk as seen from Earth. The technical name is the perigee-syzygy of the Earth-Moon-Sun system. The term “supermoon” is not astronomical, but originated in modern astrology. The association of the Moon with both oceanic and crustal tides has led to claims that the supermoon phenomenon may be associated with increased risk of events such as earthquakes and volcanic eruptions, but the evidence of such a link is widely held to be unconvincing.
The opposite phenomenon, an apogee-syzygy, has been called a micromoon, though this term is not as widespread as supermoon.
Occasionally, a supermoon coincides with a total lunar eclipse. The most recent occurrence of this was in September 2015, while the next time will be in October 2033.
The name SuperMoon was coined by astrologer Richard Nolle in 1979, arbitrarily defined as:
…a new or full moon which occurs with the Moon at or near (within 90% of) its closest approach to Earth in a given orbit (perigee). In short, Earth, Moon and Sun are all in a line, with Moon in its nearest approach to Earth.