Kuiper Belt object
A Kuiper Belt object is an icy body orbiting beyond Neptune in the Kuiper Belt, such as Pluto or Arrokoth.
A Kuiper Belt object, or KBO, is a small body orbiting the Sun in the region beyond Neptune, between about 30 and 50 times Earth's distance from the Sun. More than 3,000 have been discovered since the first after Pluto, called 1992 QB1 and later named Albion, was found in 1992.
KBOs are mixtures of rock and ices such as water, methane and nitrogen. Their colours range from grey to deep red, the red coming from organic compounds altered by radiation. Pluto, Eris, Haumea and Makemake are the largest, classed as dwarf planets.
NASA's New Horizons spacecraft flew past Pluto in 2015 and the small KBO Arrokoth in 2019. KBOs probably supply many of the short-period comets, which are knocked inwards by Neptune's gravity. Some dust from these comets may reach Earth as micrometeorites, but no meteorite has been confirmed as coming directly from the Kuiper Belt.
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Level: Explorer Ages 10 and up