Binary asteroid

A binary asteroid is a system of two asteroids orbiting their common center of mass, in analogy with binary stars. 243 Ida was the first binary asteroid to be identified when the Galileo spacecraft did a flyby in 1993. Since then numerous binary asteroids have been detected.

When both binary asteroids are similar in size, they are sometimes called "binary companions",^[1] "double asteroids" or "doublet asteroids". A good example of true binary companions is the 90 Antiope system. Binary asteroids with a small satellite, called a "moonlet", have been more commonly observed (see 22 Kalliope, 45 Eugenia, 87 Sylvia, 107 Camilla, 121 Hermione, 130 Elektra, 243 Ida, 283 Emma, 379 Huenna, etc.).^[1] They are also called high size ratio binary asteroid systems.

Paired impact craters, such as the Clearwater Lakes in Canada, may have been formed by binary asteroids.

Several theories have been posited to explain the formation of binary-asteroid systems. Recent work suggests that most of them have a significant macro-porosity (a "rubble-pile" interior). The satellite orbiting around large main-belt asteroids such as 22 Kalliope, 45 Eugenia or 87 Sylvia could have formed by disruption of a parent body after impact or fission after an oblique impact. Trans-Neptunian binaries may have formed during the formation of the Solar System by mutual capture or three-body interaction. Near-Earth asteroids, which orbit in the inner part of the Solar System, may have split by tidal disruption after a close encounter with a terrestrial planet. A possible explanation for the relatively greater occurrence of binary asteroids near or inside of Earth's orbit was described in the journal Nature (10 June 2008): this theory states that when solar energy (see YORP effect) spins a “rubble pile” asteroid to a sufficiently fast rate, material is thrown from the asteroid’s equator. This process also exposes fresh material at the poles of the asteroid.^[2][3]

See also

• List of minor planets with moons
• Yarkovsky-O'Keefe-Radzievskii-Paddack effect (YORP effect)

References

1. ^ ^{a b} "Satellites and Companions of Minor Planets". IAU / Minor Planet Center. 2009-09-17. http://www.cbat.eps.harvard.edu/minorsats.html. Retrieved 2011-01-08. 
2. ^ Walsh, Kevin J.; Richardson, DC; Michel, P (June 2008). "Rotational breakup as the origin of small binary asteroids.". Nature 454 (7201): 188–191. Bibcode 2008Natur.454..188W. doi:10.1038/nature07078. PMID 18615078. 10.1038/nature07078. 
3. ^ Study Puts Solar Spin on Asteroids, their Moons & Earth Impacts Newswise, Retrieved 14 July 2008.