Double planet

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 (IAU) 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.We might look upon the Moon, then, as neither a true satellite of the Earth nor a captured one, but as a planet in its own right, moving about the Sun in careful step with the Earth. From within the Earth–Moon system, the simplest way of picturing the situation is to have the Moon revolve about the Earth; but if you were to draw a picture of the orbits of the Earth and Moon about the Sun exactly to scale, you would see that the Moon's orbit is everywhere concave toward the Sun. It is always 'falling toward' the Sun. All the other satellites, without exception, 'fall away' from the Sun through part of their orbits, caught as they are by the superior pull of their primary planets – but not the Moon. 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 (IAU) 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 1998 WW31.