User:Paine Ellsworth/Double planet
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Double planet(link)
- Revision as of 13:35, 29 August 2010 (UTC)
In astronomy, double planet and binary planet are informal terms used to describe a binary system of two astronomical objects that each satisfy the definition of planet and that are near enough to each other to have a significant gravitational effect on each other compared with the effect of the star(s) they orbit. One unofficial requirement is that the objects orbit a common center of gravity, the barycenter, that is above both their surfaces.[citation needed]
Similarly, there are also binary asteroids (also known as double minor planets) such as 90 Antiope, and binary Kuiper belt objects (KBOs) such as (79360) 1997 CS29 and 1998 WW31. As of 2009, there are no officially classified double planets in our Solar system. The European Space Agency has referred to the Earth–Moon system as a type of double planet.[1] The IAU General Assembly in August, 2006, considered a proposal that Pluto and Charon be reclassified as a type of double planet, however a final decision has not been rendered.[2]