What is "double planet"

n. 1 a planet with a moon large enough to be considered a planet, were the planet not there, having a substantial portion of the system's overall mass. 2 a pair of planemos in orbit around each other, where the barycenter of their orbits lies outside of both planemos, which in turn is in orbit about a star. 3 a pair of planemos in orbit around each other, where the barycenter of their orbits lies outside of both planemos. 4 a planemo with a moon large enough to be considered a planemo, having a substantial portion of the system's overall mass.

In astronomy, a double planet (also binary planet) is a binary system where both objects are of planetary mass. The term is not recognized by the International Astronomical Union and is therefore not an official classification. At its 2006 General Assembly, the International Astronomical Union considered a proposal that Pluto and Charon be reclassified as a double planet, but the proposal was abandoned in favor of the current definition of planet. In promotional materials advertising the SMART-1 mission and pre-dating the IAU planet definition, the European Space Agency once referred to the Earth– Moon system as a double planet.

Some binary asteroids with components of roughly equal mass are sometimes informally referred to as double minor planets. These include binary asteroids 69230 Hermes and 90 Antiope and binary Kuiper belt objects (KBOs) 79360 Sila–Nunam and .