Solar system · Outer edge

The Kuiper Belt

The disk of icy worlds beyond Neptune, from 30 to about 50 AU: Pluto, Eris, Haumea, Makemake and thousands of smaller bodies left over from the birth of the planets.

Classical belt Second belt? (70 to 90 AU) 3:2 (Pluto) 2:1 5:2 perihelion at Neptune, 30 AU perihelion 40 AU 30 40 50 60 70 80 90 100 Average distance from the Sun, AU 0 0.2 0.4 0.6 0.75+ Eccentricity Pluto: 39.236 AU, eccentricity 0.2444, 2376 kmPluto Eris: 67.996 AU, eccentricity 0.437, 2326 kmEris Haumea: 43.005 AU, eccentricity 0.196, 1595 kmHaumea Makemake: 45.511 AU, eccentricity 0.16, 1430 kmMakemake Gonggong: 66.894 AU, eccentricity 0.503, 1230 kmGonggong Quaoar: 43.148 AU, eccentricity 0.036, 1110 kmQuaoar Sedna: 549.541 AU, eccentricity 0.861, 995 kmSedna (550 AU) Orcus: 39.336 AU, eccentricity 0.222, 910 km Salacia: 42.115 AU, eccentricity 0.103, 866 km Máni: 41.595 AU, eccentricity 0.149, 796 km Achlys: 39.628 AU, eccentricity 0.175, 772 km Aya: 47.298 AU, eccentricity 0.128, 768 km Chiminigagua: 58.786 AU, eccentricity 0.3949, 742 km Varda: 45.538 AU, eccentricity 0.143, 740 km Ixion: 39.351 AU, eccentricity 0.244, 697 km Goibniu: 41.809 AU, eccentricity 0.076, 680 km Ritona: 41.553 AU, eccentricity 0.024, 679 km 2015 RR245: 81.3 AU, eccentricity 0.586, 670 km Varuna: 43.178 AU, eccentricity 0.053, 668 km 2014 UZ224: 109.93 AU, eccentricity 0.648, 635 km Gǃkúnǁʼhòmdímà: 74.587 AU, eccentricity 0.496, 614 km Uni: 43.003 AU, eccentricity 0.1462, 610 km Chaos: 46.109 AU, eccentricity 0.111, 600 km 2015 BP519: 449 AU, eccentricity 0.9215, 584 km 2013 FZ27: 48.14 AU, eccentricity 0.2196, 570 km 2012 VP113: 262.3 AU, eccentricity 0.6931, 450 km2012 VP113 (262 AU) Leleākūhonua: 1190 AU, eccentricity 0.945, 220 kmLeleākūhonua (1,190 AU)
Each dot is a large object beyond Neptune, placed by its average distance from the Sun and how stretched its orbit is, sized by diameter. Vertical lines mark orbits in step with Neptune; objects above the lower curve cross inside Neptune's orbit. The distance scale is logarithmic; Sedna and others beyond 110 AU sit at the right edge and very stretched orbits at the top. Click a dot to open its page.
Known objects
4,000+beyond Neptune
Estimated
100,000+larger than 100 km
Classical belt
42 to 48 AUnear-circular orbits
Largest
Eris and Plutoabout 2,350 km
Visited
Pluto, ArrokothNew Horizons

The 27 largest known objects beyond Neptune

Every known body beyond Neptune about 500 km or larger, plus a few notable smaller ones, from the site's planets dataset. Five are recognized dwarf planets; most of the rest are probably round enough to qualify. Sort any column; the buttons filter by population.

27 shown
ObjectPopulationDiameter kmAverage distance AUClosest AUEccentricityTilt °MoonsStatus
PlutoResonant with Neptune2,37639.23629.6460.244417.165dwarf planet (IAU)
ErisScattered disk2,32667.99638.2840.43743.871dwarf planet (IAU)
HaumeaClassical belt1,59543.00534.5860.19628.212dwarf planet (IAU)
MakemakeClassical belt1,43045.51138.210.1629.031dwarf planet (IAU)
GonggongScattered disk1,23066.89433.2350.50330.871dwarf planet candidate
QuaoarClassical belt1,11043.14841.6010.0367.991dwarf planet candidate
SednaDetached and sednoids995549.54176.2230.86111.930dwarf planet candidate
OrcusResonant with Neptune91039.33630.6140.22220.561dwarf planet candidate
SalaciaClassical belt86642.11537.7610.10323.931dwarf planet candidate
MániScattered disk79641.59535.410.14917.70dwarf planet candidate
AchlysResonant with Neptune77239.62832.6990.17513.550dwarf planet candidate
AyaResonant with Neptune76847.29841.2590.12824.340dwarf planet candidate
ChiminigaguaScattered disk74258.78635.5720.394933.1210dwarf planet candidate
VardaClassical belt74045.53839.0260.14321.511dwarf planet candidate
IxionResonant with Neptune69739.35129.740.24419.670dwarf planet candidate
GoibniuScattered disk68041.80938.6310.07622.040dwarf planet candidate
RitonaScattered disk67941.55340.5610.02419.260dwarf planet candidate
2015 RR245Scattered disk67081.333.70.5867.580possible dwarf planet
VarunaClassical belt66843.17840.9090.05317.140dwarf planet candidate
2014 UZ224Scattered disk635109.9338.6950.64826.7790dwarf planet candidate
GǃkúnǁʼhòmdímàScattered disk61474.58737.5850.49623.330dwarf planet candidate
UniClassical belt61043.00336.7160.146219.40dwarf planet candidate
ChaosClassical belt60046.10941.0130.11112.020dwarf planet candidate
2015 BP519Scattered disk58444935.20.921554.110possible dwarf planet
2013 FZ27Resonant with Neptune57048.1437.570.2196140possible dwarf planet
2012 VP113Detached and sednoids450262.380.520.693124.060possible dwarf planet
LeleākūhonuaDetached and sednoids2201190650.94511.670extreme TNO (sednoid)

The belt has four populations, sorted by how Neptune shaped their orbits

  • Resonant objects circle the Sun in a whole-number ratio with Neptune. Pluto and the other plutinos make two orbits for every three of Neptune's, at 39.4 AU, which keeps them safe even when they cross Neptune's orbit. Neptune captured them as it migrated outward early in the solar system's history.
  • The classical belt, from about 42 to 48 AU, holds objects on nearly circular orbits. Its cold, flat core, including Arrokoth, probably formed where it is and has barely been disturbed for 4.5 billion years.
  • The scattered disk holds objects thrown onto long, tilted orbits by close passes with Neptune. Eris and Gonggong are here, and it is the main source of Jupiter-family comets.
  • Detached objects never come close enough to Neptune to be disturbed. Sedna and Leleākūhonua are the extreme cases; why their orbits are so stretched is the puzzle behind Planet Nine.

Pluto was found in 1930; the next Kuiper Belt object took until 1992

Kenneth Edgeworth in 1943 and Gerard Kuiper in 1951 speculated about bodies beyond Neptune. David Jewitt and Jane Luu found the first, 1992 QB1 (now named Albion), from Mauna Kea after a five-year search. More than 4,000 are now known, and astronomers estimate more than 100,000 over 100 km across. The discovery of Eris, about Pluto's size, in 2005 led the IAU to create the dwarf planet category in 2006. The belt's total mass is only a few percent of Earth's.

New Horizons flew past Pluto in 2015 and Arrokoth in 2019, and is still in the belt

NASA's New Horizons showed Pluto has nitrogen glaciers, mountains of water ice and a thin, hazy atmosphere. On January 1, 2019, it flew past Arrokoth, a 36 km pair of joined lobes that gently merged as the solar system formed, the most distant and most primitive object yet visited. Now about 66 AU out, it measures dust and the solar wind, takes distant images of other Kuiper Belt objects and is expected to cross the termination shock, the inner edge of the heliosphere's boundary, between 2029 and 2040.

The belt seems to end at 50 AU, but a second belt may lie at 70 to 90 AU

The number of classical objects drops sharply beyond the 2:1 resonance at 47.8 AU, an edge known as the Kuiper cliff. In 2024 a Subaru Telescope survey for New Horizons found 11 objects at 70 to 90 AU with a gap from 55 to 70 AU, hinting at a second, more distant belt. New Horizons' dust counter also keeps recording more dust than expected, another hint that the belt reaches farther out.

The Rubin Observatory should multiply the known Kuiper Belt objects several times over

The Vera C. Rubin Observatory, which began its ten-year survey of the southern sky in 2025, is expected to find tens of thousands of new objects beyond Neptune. That should settle whether the second belt is real and whether distant orbits cluster as Planet Nine predicts. China's planned Shensuo probes to the edge of the heliosphere would also pass through the belt. Moons of the dwarf planets · The Oort Cloud