Cosmos The Cosmic Journey

KUIPER BELT

sometimes called the Edgeworth-Kuiper belt, is a region of the Solar System beyond the planets, extending from the orbit of Neptune (at 30AU) to approximately 50 AU from the Sun.It is similar to the asteroid belt, but it is far larger-20 times as wide and 20 to 200 times as massive. Like the asteroid belt, it consists mainly of small bodies, or remnants from the Solar System's formation. Although many asteroids are composed primarily ofrock and metal, most Kuiper belt objects are composed largely of froen volatiles (termed "ices"), such as methane, ammonia and water. The Kuiper belt is home to three officially recognized dwarf planets: Pluto,Haumea, and Makemake. Some of the Solar System's moons, such as Neptune's Tritonand Saturn's Phoebe, are also believed to have originated in the region.
The Kuiper belt was named after Dutch-American astronomer Gerard Kuiper, though his role in hypothesising it has been heavily contested. Since it was discovered in 1992,the number of known Kuiper belt objects (KBOs) has increased to over a thousand, and more than 100,000 KBOs over 100 km (62 mi) in diameter are believed to exist.The Kuiper belt was initially thought to be the main repository for periodic comets, those with orbits lasting less than 200 years. However, studies since the mid-1990s have shown that the belt is dynamically stable, and that comets' true place of origin is the scattered disc, a dynamically active one created by the outward motion of Neptune 4.5 billion years ago;scattered disc objects such as Erishave extremely eccentric orbits that take them as far as 100 AU from the Sun.

The Kuiper belt should not be confused with the hypothesized Oort cloud, which is a thousand times more distant and is not flat. The objects within the Kuiper belt, together with the members of the scattered disc and any potential Hills cloud or Oort cloud objects, are collectively referred to as trans-Neptunian objects (TNOs).

Pluto is the largest member of the Kuiper belt, and the second largest known TNO, the largest being Eris in the scattered disc.Originally considered a planet, Pluto's status as part of the Kuiper belt caused it to be reclassified as a "dwarf planet" in 2006. It is compositionally similar to many other objects of the Kuiper belt, and its orbital period is characteristic of a class of KBOs, known as "plutinos", that share the same 2:3 resonancewith Neptune.