Online Encyclopedia Search Tool

Your Online Encyclopedia


Online Encylopedia and Dictionary Research Site

Online Encyclopedia Free Search Online Encyclopedia Search    Online Encyclopedia Browse    welcome to our free dictionary for your research of every kind

Online Encyclopedia

Trans-Neptunian object

A Trans-Neptunian object (TNO) is any object in the solar system with all or most of its orbit beyond that of Neptune. The Kuiper belt and Oort cloud are names for some subdivisions of that volume of space. Pluto is a trans-Neptunian object, and if it had been discovered today, it might not have been called a planet.

Gravity, the attracting force between all matter, also attracts planets. Due to the changes in the orbits of the known planets in the early 1900s, it was assumed that there was one or more planets beyond Neptune, but not yet identified. (See Planet X.) This search for these led to the discovery of Pluto, and since then a few other significant objects have been found. These are still too small to explain the perturbations, though, and revised estimates of Neptune's mass showed that the problem was fictitious.

Trans-Neptunian objects of note:

The hypothetical companion star Nemesis would have fallen under the definition of trans-Neptunian object, but it appears that no such star actually exists.

A fuller list of objects is being compiled in the list of trans-Neptunian objects.

External links

The Minor Planets
Vulcanoids | Main belt | Groups and Families | Near-Earth objects | Jupiter Trojans
Centaurs | Trans-Neptunians | Damocloids | Comets | Kuiper Belt | Oort Cloud
(For other objects and regions, see: Binary asteroids, Asteroid moons and the Solar system)
(For a complete listing, see: List of asteroids)

The Solar System
Sun | Mercury | Venus | Earth (Moon) | Mars | Asteroids
Jupiter | Saturn | Uranus | Neptune | Pluto | Kuiper belt | Oort cloud
See also astronomical objects and the solar system's list of objects, sorted by radius or mass

Last updated: 11-03-2004 14:52:19