Supermoon

A full or new moon occurring near perigee, the closest point to Earth in the Moon’s orbit. It appears slightly larger and brighter than a full or new moon near apogee.

Lunar orbit: The Moon’s path around Earth, shaped mainly by gravity and made elliptical by perturbations. Its changing Earth–Moon distance creates perigee, where a supermoon can occur.
Micromoon: A full or new moon occurring near apogee, the farthest point from Earth in the Moon’s orbit. It is the orbital-distance counterpart to a supermoon.
Richard Nolle: An American astrologer who introduced the term “supermoon” in 1979. His definition helped establish the popular name and its distance threshold.
Tidal force: The difference in gravitational pull across an extended body, caused by another body's gravity. The Moon’s close approach slightly strengthens its contribution to tides.
Perigee: The point in an orbit at which an object is closest to the body it orbits. A supermoon’s full or new phase must occur near this point.
Apogee: The point in an orbit at which an object is farthest from Earth. A full moon near apogee appears smaller than one near perigee.
Perigee-syzygy: An alignment of the Sun, Earth, and Moon occurring near the Moon’s closest orbital point to Earth. This technical phrase describes the astronomical configuration commonly called a supermoon.
Spring tide: A tide with an especially large range, occurring near new and full moons when solar and lunar tidal effects align. A perigean spring tide combines lunar proximity with the alignment associated with spring tides.
Lunar phase: The changing fraction of the Moon’s sunlit hemisphere visible from Earth. Only a full or new phase qualifies for the common supermoon definition.
Lunar eclipse: An event in which Earth’s shadow falls on the Moon. A supermoon describes phase and distance, not an eclipse; the events only sometimes coincide.

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