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Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest known trans-Neptunian object by volume, by a small margin, but is less massive than Eris.
In a draft resolution for the IAU definition of planet, both Pluto and Charon were considered planets in a binary system. [20] [c] The IAU currently says Charon is not considered a dwarf planet but rather a satellite of Pluto, though the idea that Charon might qualify as a dwarf planet may be considered at a later date. [96]
[a] Originally considered a planet, Pluto's status as part of the Kuiper belt caused it to be reclassified as a dwarf planet in 2006. It is compositionally similar to many other objects of the Kuiper belt, and its orbital period is characteristic of a class of KBOs, known as " plutinos ," that share the same 2:3 resonance with Neptune.
Pluto was considered a planet up until 2006, when researchers at the International Astronomical Union voted to "demote" it to dwarf planet.
Pluto is so small and so remote from the Sun and the Earth that it was not discovered until 1930. [3] It was classified as a planet at the time and remained as such for 76 years until 2006, when the International Astronomical Union reclassified it as a dwarf planet, as it belongs to a belt of many similar small objects. [4]
For the giant planets, the "radius" is defined as the distance from the center at which the atmosphere reaches 1 bar of atmospheric pressure. [ 11 ] Because Sedna and 2002 MS 4 have no known moons, directly determining their mass is impossible without sending a probe (estimated to be from 1.7x10 21 to 6.1×10 21 kg for Sedna [ 12 ] ).
It is about half the diameter and an eighth the mass of Pluto, a dwarf planet that resides in a frigid region of the outer Solar System called the Kuiper Belt, beyond the most distant planet ...
For 76 years, Pluto was considered out solar system's ninth planet. So what caused it to lose its planetary status? Find out on this episode of "Space, Down to Earth"!