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Published 28th March 2013 by

The Kuiper belt is an area of the solar system extending from the orbit of Neptune (at 30 AU) to 50 AU from the Sun. The objects within the Kuiper Belt together with the members of the scattered disk extending beyond are collectively referred to as trans-Neptunian objects.
Astronomical Objects Series
  1. Guide to the Constellations and Mythology
  2. What are Asteroids, Meteors and Comets?
  3. Binary Stars and Double Stars
  4. Variable Stars
  5. Supernova and Supernovae
  6. Types of Nebula and Nebulae
  7. What Is a Black Hole? Black Holes Explained - From Birth to Death
  8. Quasars
  9. Pulsars - The Universe's Gift to Physics
  10. What is inside a Neutron Star?
  11. Gamma Ray Bursts
  12. Kuiper Belt
  13. What is an Exoplanet?
  14. Galaxy Types and Galaxy Formation
  15. The Messier Catalogue
  16. The Caldwell Catalogue
  17. 25 Stunning Sights Every Astronomer Should See
The Kuiper Belt

The Kuiper Belt


Over 800 Kuiper belt objects (KBOs) have been discovered in the belt, almost all of them since 1992. Among the largest are Pluto and Charon, but since the year 2000 other large objects that approached their size were identified. 50000-Quaoar, discovered in 2002, which is a KBO, is half the size of Pluto and is larger than the largest asteroid, 1-Ceres 2005-FY9 and 2003-EL61, both announced on 29 July 2005, are larger still. Other objects, such as 28978-Ixion (discovered in 2001) and 20000-Varuna (discovered in 2000) while smaller than Quaoar, are nonetheless quite sizable. Sedna, a small red planetoid with a diameter roughly half-way between Pluto and Quaoar, was first sighted on November 14th, 2003. The exact classification of these objects is unclear since they are probably fairly different from the asteroids of the asteroid belt. The largest recent discovery is 2003-UB313, codenamed Xena.

It has led scientists to question the definition of the term Planet, as it is larger than Pluto and has already been called a tenth planet by some.


On July 30th, 2005 the discovery of a tenth planet was announced by its discoverer Michael E. Brown. Its official scientific name is 2003 UB313 or "Eris" but its informal codename used by its discoverers is Xena. The International Astronomical Union published the definition of the term "planet" in early September 2006, which decided that 2003 UB313 is not classified as a planet, nor is Pluto.

The dwarf planet is very cold and has an almost white surface. Probably it is covered with frozen Methane. Its axis is lent for 44 degrees compared to the other planets. This is one reason why it wasn't discovered earlier. The dwarf planet is located in the Kuiper belt and is slightly bigger than Pluto.

Eris has the moon with the name Dysnomia, which has is at least one-tenth of Eris' size.

2003 UB313 and Moon

2003 UB313 and Moon


  • Distance from the Sun: 97 AU
  • Diameter: 2390 km (0.188 times Earth)
  • Orbit period: 557 years = 203,440 days

New Horizons

NASA's New Horizons probe is officially set to explore the Kuiper Belt. The probe's next mission will take it about a billion miles past Pluto. Having captured the most detailed images of Pluto we've ever seen, NASA's New Horizons space probe is getting a new mission. New Horizons will be going deeper into the Kuiper Belt and is en-route to the small icy object known as 2014 MU69. This rock was first discovered by the Hubble telescope in June 2014. It should arrive at 2014 MU69 on January 1st, 2019 and start transmitting back valuable information about what lies within the Kuiper Belt.

Tutorial Series

This post is part of the series Astronomical Objects. Use the links below to advance to the next tutorial in the couse, or go back and see the previous in the tutorial series.

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