00:00In astronomy, a dwarf planet is a celestial object in the solar system of intermediate class between a planet and a
00:05small body in the solar system.
00:07The term was adopted on August 24, 2006 by the International Astronomical Union (IAU), after a debate to clarify
00:13the classification of objects in orbit around the Sun.
00:16This was notably precipitated by the discovery of Eris, an object of similar size to Pluto, then considered to be
00:22a planet,
00:23and faced with the prospect of discovering many other objects in the future of a size that could make them
00:27planets.
00:28More specifically, the IAU defines a dwarf planet as "a celestial body that" is in orbit around
00:34of the Sun,
00:35b. has sufficient mass for its gravity to overcome the cohesive forces of the solid body and
00:39maintains it in hydrostatic equilibrium.
00:41in an almost spherical shape, c. has not eliminated all bodies capable of moving in a nearby orbit,
00:47d. is not a satellite.
00:49Initially, three dwarf planets were designated: Ceres, Pluto, and Eris, to which Omea and Makemake were later added in 2008.
00:56which brings to 5 the number of objects recognized as dwarf planets by the IAU.
01:00The known objects most likely to be added to this category in the future are Gong-Gong, Quaor, and Sedna.
01:06and Orcus.
01:07The total number of dwarf planets in the solar system is unknown because it is difficult to determine if a body is in equilibrium.
01:12hydrostatic
01:13requires at least one flyby by a space probe, which has only been the case for Ceres and
01:17Pluto.
01:17Many large trans-Neptunian objects, however, have natural satellites.
01:21This allows us to precisely determine their mass and therefore estimate their density.
01:25The need to distinguish between planets and another category of objects, including Pluto, has been clearly apparent since 2000 in
01:31the works of Alan Stern, Harold F.
01:34Levison, Stephen Sauter, and Jean-Luc Margot, along with numerous astronomers, particularly Americans including Alan Stern,
01:40initially opposed the introduction of this new term due to the loss of the status of
01:44planet for Pluto.
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