What is the Kuiper Belt?
The Kuiper Belt is a huge, doughnut-shaped region of icy objects beyond Neptune. It is home to dwarf planets such as Pluto and is the source of many short-period comets.
The Kuiper Belt stretches from Neptune's orbit, about 30 times Earth's distance from the Sun, out to around 50 times that distance. It is similar to the asteroid belt but far larger, perhaps 20 times as wide, and its objects are made mostly of frozen water, methane and ammonia rather than rock and metal.
The belt is named after Dutch-American astronomer Gerard Kuiper, who discussed such a region in 1951. The first Kuiper Belt object after Pluto and its moon Charon was discovered in 1992. Since then, astronomers have found thousands more, including the dwarf planets Haumea and Makemake.
Visiting the Kuiper Belt
NASA's New Horizons spacecraft flew past Pluto in 2015, revealing mountains of ice and a heart-shaped plain. In 2019, it flew past Arrokoth, a small object shaped like a snowman, the most distant object ever explored up close.
Did You Know?
The discovery of many Pluto-sized objects in the Kuiper Belt led astronomers to reclassify Pluto as a dwarf planet in 2006.