Portal:Astronomy/Featured/October 2007

The Kuiper belt (pronounced, to rhyme with "viper"), sometimes called the Edgeworth-Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune (at 30 AU) to approximately 55 AU from the Sun. It is similar to the asteroid belt, although it is far larger; 20 times as wide and 20–200 times as massive. Like the asteroid belt, it consists mainly of small bodies (remnants from the Solar System's formation) and at least one dwarf planet – Pluto. But while the asteroid belt is composed primarily of rock and metal, the Kuiper belt is composed largely of ices, such as methane, ammonia, and water.

Since discovery, the number of known Kuiper belt objects (KBOs) has increased to over a thousand, and more than 70,000 KBOs over 1 km in diameter are believed to reside there. The Kuiper belt is believed to be the main repository for periodic comets, those with orbits lasting less than 200 years. The centaurs, comet-like bodies that orbit among the gas giants, are also believed to originate there, as are the scattered disc objects such as Eris—KBO-like bodies with extremely large orbits that take them as far as 100 AU from the Sun. Neptune's moon Triton is believed to be a captured KBO.

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