The term Trans-Neptunian object (TNO) is used to describe those objects that orbit the sun at a greater average distance than Neptune. TNO's are rarely imaged by amateur astronomers because - with the obvious exception of Pluto - they are extremely faint. Few get brighter than magnitude 19!
Various sub-divisions of TNO's exists.
|Haumea||Classed as a plutoid, that is a dwarf planet beyond the orbit of Neptune. Its status as a dwarf planet means it is presumed to be massive enough to have been rounded by its own gravity, but not to have cleared its neighbourhood of similar objects. Haumea may be in a 12:7 orbital resonance with Neptune.||Click here|
|Ixion||Ixion is in a 2:3 orbital resonance with Neptune and so is a plutino. It is also a potential dwarf planet.||Click here|
|Makemake||Makemake is the second brightest TNO's and is classified as a dwarf planet and as a plutoid.||Click here|
|Orcus||Orcus is a large plutino (an object in 2:3 orbital resonance with Neptune).||Click here|
|Quaoar||Quaoar is a potential dwarf planet orbiting the Sun in the Kuiper belt.||Click here|
|Varuna||Varuna is a large classical Kuiper Belt object (KBO), a cubewano and a potential dwarf planet.||Click here|
The term Cis-Neptunian object is used for all sub-planetary bodies orbiting the Sun between the orbits of Jupiter and Neptune including the icy asteroids known as centaurs and the Neptunian Trojans.
|2060 Chiron||A centaur that also shows cometary activity - hence classified as both an asteroid and a comet.||Pending|
|60558 Echeclus||A centaur that also shows cometary activity - hence classified as both an asteroid and a comet.||Click here|
|52872 Okyrhoe||Suspected of showing cometary activity.||Pending|
|95626 2002 GZ32||A Uranus-crossing asteroid.||Click here|
|120061 2003 CO1||A bright centaur (magnitude 19.5!)||Click here|
Martin Nicholson - Daventry, United Kingdom. The image was taken using the facilities provided by the Sierra Stars Observatory Network (SSON).
This page was last updated on February 5th 2011.