Pluto in enhanced colour, photographed by NASA's New Horizons spacecraft

Dwarf planets and the outer solar system

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Beyond Neptune lies a belt of icy worlds left over from the birth of the solar system, and among them the largest are the dwarf planets: bodies big enough for their own gravity to make them round, but not big enough to sweep their orbits clear.[1] The International Astronomical Union recognises five, Ceres, Pluto, Haumea, Makemake and Eris, and says perhaps more than a hundred more are waiting to be found.[1] The belt itself begins at Neptune's orbit, about 30 astronomical units from the Sun, and astronomers think it holds millions of small icy objects.[2] New survey telescopes are now finding them in numbers: in October 2026 the Rubin Observatory announced its first dwarf-planet candidate, 2026 ED138, hidden until then in a crowded part of the sky.[3] The guide What is a dwarf planet? explains the definition and the candidates; The Kuiper belt and beyond describes the region and how its objects are found.

Notable

PlutoThe largest known body in the Kuiper belt and the first dwarf planet, counted as the ninth planet from 1930 to 2006 and visited by New Horizons in July 2015.ErisThe dwarf planet about the size of Pluto whose discovery in 2005 led to Pluto's reclassification; it orbits about 68 au from the Sun once every 557 years.HaumeaA dwarf planet shaped like a football by its four-hour spin, with two moons and a ring found in 2017, orbiting about 43 au from the Sun once every 285 years.MakemakeA dwarf planet slightly smaller than Pluto and the second-brightest object in the Kuiper belt, with frozen methane on its surface and a moon found in 2016.CeresThe largest body in the asteroid belt and the only dwarf planet of the inner solar system, found in 1801 and orbited by NASA's Dawn from 2015 to 2018.GonggongA dwarf-planet candidate about 1,230 km across on a tilted, elongated orbit far beyond Pluto, with a small moon, Xiangliu, found in Hubble images.QuaoarA dwarf-planet candidate about 1,110 km across on a nearly circular orbit beyond Pluto, with a moon, Weywot, and two rings where none were expected.SednaA dwarf-planet candidate about 995 km across on one of the most distant orbits known, never closer to the Sun than 76 au and about 12,700 years around.OrcusA dwarf-planet candidate about 917 km across on an orbit much like Pluto's, in the same resonance with Neptune, with a large moon, Vanth, about half its size.2026 ED138A dwarf-planet candidate found by the Rubin Observatory beyond Neptune and announced on 27 October 2026, an icy world that may be 600 to 1,500 km across.

Guides

Terms

Dwarf planetKuiper beltTrans-Neptunian object
All terms in the Glossary

Sources

  1. [1]NASA, Pluto & Dwarf Planets — science.nasa.gov, retrieved November 5, 2026
  2. [2]NASA, Kuiper Belt: Facts — science.nasa.gov, retrieved November 5, 2026
  3. [3]NSF–DOE Vera C. Rubin Observatory, NSF–DOE Vera C. Rubin Observatory Reveals Its First Dwarf Planet Candidate in Our Solar System — rubinobservatory.org, retrieved November 5, 2026