[SunkenCiv]

Minor Planets Stick Together
by Selby Cull
June 23, 2006

In January 2006, astronomers focused the Hubble Space Telescope on an icy rock near the orbit of Uranus — and found twins. The object, known as 2002 CR46, turned out to be a binary: a minor planet the size of Rhode Island orbiting another the size of Connecticut at a distance of 1,300 kilometers (800 miles)... Many main-belt asteroids and Kuiper Belt objects (KBOs) are binary, but 2002 CR46 is the first known binary Centaur... The sticking power of 2002 CR46 hints at the existence of binary comets. Most short-period comets begin as KBOs, transition to Centaurs, then are kicked into the inner solar system by giant planets. And if binary Centaurs can survive multiple close encounters with these behemoths, they might also survive the final leap to become binary comets... In an upcoming paper in Icarus, Noll’s team will report on 2002 CR46 and a second binary Centaur — 2003 FX128 — bringing the total number of known double minor-planets to almost 100. No longer statistically unlikely anomalies, binaries now seem to be a natural outcome for all kinds of minor planets.

[SunkenCiv]

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Hubble imaged the first binary Centaur, 2002 CR46, last January. Though it routinely crosses paths with the giant planets, the pair has somehow stuck together. Courtesy Keith Noll / Space Telescope Science Institute.

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