A supermoon is a full moon that has the closest distance from the Earth it reaches in its elliptic orbit, resulting in a larger-than-usual apparent size of the lunar disc.
The name supermoon was coined by astrologer Richard Nolle in 1979. He defined it as 'a new or full moon which occurs with the Moon at or near (within 90 per cent of) its closest approach to Earth in a given orbit or perigee'.
However, on the supermoon night, the Earth, the Moon and the Sun are all in a line, with the Moon in its nearest approach to the Earth.
The term supermoon has its origin in modern astrology and the opposite phenomenon, an apogee syzygy, has been called a micromoon which often goes un-noticed. It is said that the next supermoon will occur on January 2, 2018.