Glossary · Thiên văn học
Kuiper Belt
A doughnut-shaped region of icy objects beyond Neptune's orbit. Its main region runs from about 30 AU to about 50 AU, and it is where Pluto and several other dwarf planets reside.
NASA describes the Kuiper Belt as a doughnut-shaped region of icy objects beyond the orbit of Neptune. Its inner edge begins at Neptune's orbit, about 30 AU from the Sun; the main region ends around 50 AU. Overlapping that outer edge is the scattered disk, which continues outward to nearly 1,000 AU — with some bodies on orbits that go even farther beyond.
The region holds hundreds of thousands of bodies 100 km across or larger, along with Pluto, other dwarf planets, comets and millions of icy worlds left over from the formation of the Solar System. Even so, the total mass of all the material there is estimated to be no more than about 10% of Earth's mass.
Do not confuse the Kuiper Belt with the Oort Cloud. NASA describes the Oort Cloud as a much more distant region of icy, comet-like bodies that surrounds the Solar System — including the Kuiper Belt itself. The Kuiper Belt, by contrast, is a puffed-up disk whose objects have been observed directly: more than 2,000 trans-Neptunian objects had been catalogued as of September 2026.