Double Planet

In astronomy, double planet and binary planet are informal terms used to describe a binary system where both objects are of planetary mass. Though not an official classification, the European Space Agency has referred to the Earth–Moon system as a double planet. The IAU General Assembly in August 2006 considered a proposal that Pluto and Charon be reclassified as a double planet, but the proposal was abandoned.

There are also binary asteroids (also known as double minor planets) such as 90 Antiope, and binary Kuiper belt objects (KBOs) such as 79360 Sila–Nunam and 1998 WW₃₁.