Asteroid moon

An asteroid moon is an asteroid that orbits another asteroid. It is thought that many asteroids may possess moons, in some cases quite substantial in size. Asteroids with moons are commonly referred to as binary asteroids. The term double asteroid is sometimes used for systems in which the asteroid and its moon are roughly the same size.

Related Topics:
Asteroid - Orbit - Binary asteroid - Double asteroid

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The origin of asteroid moons is not currently known with certainty, and a variety of possibilities exist. A widely accepted theory is that asteroid moons are formed from debris knocked off of the primary asteroid by an impact. Other pairings may be formed when a small asteroid is captured by the gravity of a larger one.

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The first asteroid moon to be identified was Dactyl which orbits 243 Ida. It was discovered by the Galileo probe in 1993. The second was discovered around 45 Eugenia in 1998. As of February 2004, nearly 37 more asteroid moons had been discovered by Earth-bound telescopes. Asteroid moons have been discovered orbiting main belt asteroids, Trojan asteroids, near-Earth objects, and Kuiper Belt objects. In 2005, the asteroid 87 Sylvia was discovered to have two moons, making it the first known triple asteroid.

Related Topics:
Dactyl - 243 Ida - Galileo probe - 1993 - 45 Eugenia - 1998 - As of February 2004 - Telescopes - Main belt - Trojan asteroid - Near-Earth object - Kuiper Belt object - 2005 - 87 Sylvia

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An example of a double asteroid is 90 Antiope, where two equal-sized components orbit the common centre of gravity.

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