The Kuiper Belt

Another collection of a vast number of objects form a belt somewhat similar to the asteroid belt, but out beyond the orbit of Neptune between about 30 and 55AU. The belt was named the Kuiper belt after Gerard Kuiper, a pioneer in planetary astronomy. A number of Kuiper belt objects have been discovered with diameters between 100 and 400km. The Kuiper belt is thought to be the origin of many short-period (<200 years) comets. Pluto and its moon, Charon, are similar to Kuiper belt objects, which is one reason why Pluto was demoted from full planet status.

另一群数量庞大的天体形成一个带状结构，其形态与小行星带相似，但位于海王星轨道之外，大约在30到55个天文单位之间。这个带状结构以 Gerard Kuiper 命名，他是行星天文学的先驱。已发现的一些 Kuiper 带天体直径在100到400公里之间。Kuiper 带被认为是许多短周期（<200年）彗星的起源地。冥王星及其卫星卡戎与 Kuiper 带天体相似，这也是冥王星被降级为矮行星的一个原因。

Whereas objects in the main asteroid belt are mostly rocky objects, the Kuiper belt objects are thought to be mostly composed of ices. Besides water ice, there may be large quantities of frozen methane and ammonia. Besides Pluto, two other dwarf planets named Haumea and Makemake are considered to be part of the Kuiper belt.

尽管主小行星带中的天体大多为岩石类天体，柯伊伯带中的天体被认为主要由冰质组成。除了水冰之外，可能还含有大量冻结的甲烷和氨。除了冥王星外，另外两个被认定为矮行星的天体——哈伊姆和马克墨凯也被认为属于柯伊伯带。

The Kuiper belt object 2014 MU69 is a target for the New Horizons spacecraft now that it has passed Pluto.

目前，柯伊伯带天体2014 MU69已成为新视野号航天器的目标对象，因为它已经掠过冥王星。

In July 2005, a team of scientists announced the discovery of a Kuiper belt object that is similar in size to Pluto. It has been named Eris. It orbits the sun about once every 560 years, its distance varying from about 38 to 98 AU. (For comparison, Pluto travels from 29 to 49 AU in its solar orbit.) Eris has a small moon named Dysnomia. Eris, Pluto and the asteroid Ceres have been classified as dwarf planets. Solarsystem.nasa.gov

2005年7月，一组科学家宣布发现了类似冥王星大小的柯伊伯带天体。该天体被命名为厄里斯。厄里斯绕太阳公转的周期约为560年，其轨道距离变化在约38到98个天文单位之间。（相比之下，冥王星的轨道距离在29到49个天文单位之间。）厄里斯有一颗小卫星，名为迪斯诺弥亚。厄里斯、冥王星和小行星谷神星都被归类为矮行星。solarsystem.nasa.gov