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Kuiper Belt object

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In Astronomy the term Kuiper Belt object is used to refer to astronomical objects that orbit Sol, our sun, farther out than Planet Neptune.

Kuiper Belt objects have been grouped into three subcategories.[1] Many Kuiper Belt objects were found to be in orbital resonance with Planet Neptune, and are classed as resonant objects. Classical objects are Kuiper Belt objects which are not resonant with Neptune, and whose orbits are, relatively speaking, not eccentric. The final group are called scattered objects, which have long eccentric orbits, and are often deeply inclined to the ecliptic.

After the term was coined Pluto was classed as a Kuiper Belt object. Like Pluto, many Kuiper Belt objects orbit in a 2 to 3 resonance with Neptune.[2] These objects orbit Sol twice every time Neptune orbits twice. These objects are now named plutinos, named after the first and largest object in the group. Other resonant objects called onetinos are in 1 to 1 resonance. and twotinos are in 2 to 1 resonance.

Astronomy Magazine reported, in 2015, that over 1,000 Kuiper Belt objects, over 100 kilometres (62 mi) in diameter had been discovered.[3]

Other Kuiper Belt objects, not in resonance with Neptune, are classed as Classical Kuiper Belt objects (CKBO), are nicknamed cubewanos. (15760) 1992 QB, the second Kuiper Belt object, discovered in 1992, is not in resonance, and is classed as a cubewanos.

Some Kuiper Belt objects
name distance diametere discovered resonance notes
Pluto 39 AU 2,377 kilometres (1,477 mi) 1930-02-18 plutino
  • Originally classed as a planet, until too many similar objects have been discovered.
(15760) 1992 QB 44.3 AU 1992 cubewano
  • The second Kuiper Belt object to be discovered
90482 Orcus 39.5 AU 917 kilometres (570 mi) 2004-02-17 plutino
28978 Ixion 39.5 AU 710 kilometres (440 mi) 2001-05-22 plutino
38628 Huya 39.5 AU 406 kilometres (252 mi) plutino
Dysnomia
Eris 68.5 AU 2,400 kilometres (1,500 mi) 2005-01-05
  • The discovery of Eris helped trigger the demotion of Pluto's classification as a planet.[4]
Quaoar 1,100 kilometres (680 mi)
  • Quaoar is orbited by at least two debris rings, and at least one moon, Weywot[5]
Weywot 116 kilometres (72 mi)
Sedna
Haumea 49.5 AU 1,740 kilometres (1,080 mi) 2003 cubewano
Makamake
2002 AW197
(87269) 2000 OO67 64 kilometres (40 mi) 2000 scattered object

References

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  1. 1.0 1.1 Maria Velea (2006). "Kuiper Belt" (PDF). Studiisi Communicar Bacau. Archived from the original (PDF) on 2026-07-10. Retrieved 2026-07-10. The objects discovered until now in Kuiper Belt have very interesting dynamic properties. They have a very uneven distribution of orbital elements, being thus divided in three distinct dynamic classes: classical objects, resonant objects and scattered objects.
  2. Marcia Dunn (2026-05-04). "Astronomers believe they've detected an atmosphere around a tiny, icy world beyond Pluto". Associated Press. Archived from the original on 2026-05-06. Retrieved 2026-07-08 – via PBS.
  3. Eric Betz (2015-06-15). "1992 QB1: The first Kuiper Belt object opened a realm of 1,000 Plutos". Astronomy Magazine. Archived from the original on 2023-06-07. Retrieved 2026-07-08. And even as Luu and Jewitt worked to refine an orbit for their new icy dwarf planet, it became clear that the floodgates had opened. The pair found another within six months, then two more. Soon, other teams were turning up even larger Kuiper Belt objects (KBOs). Today, there are 1,000 known KBOs larger than 60 miles (100km) in diameter.
  4. "Eris". NASA Science. 2017-11-15. Archived from the original on 2026-07-04. Retrieved 2026-07-09. The discovery of Eris help trigger a debate in the scientific community that led to the International Astronomical Union's decision in 2006 to clarify the definition of a planet. Pluto, Eris, and other similar objects are now classified as dwarf planets.
  5. 5.0 5.1 Nola Taylor Tillman (2025-09-10). "The weird ringed dwarf planet Quaoar may have an extra moon, astronomers discover". Space.com. Retrieved 2026-07-08.