From Conservapedia
(Redirected from
Dwarf planet)
A
dwarf planet is a satellite of the
Sun that meets the following criteria now set by the
International Astronomical Union:
| “
| (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d)is not a satellite.[1]
| ”
|
Eris
- Main Article: Eris
The concept of "dwarf planet" properly dates to the discovery of the scatter-disk object named Eris on January 5, 2005. With the confirmation of the identification of Eris, a formal debate began on the subject of what does, and what does not, constitute a planet. The community of astronomers decided that relying on history and tradition simply would not serve. The eight celestial bodies that now remain under the present definition of planet do not share their orbits with any other objects. The objects now called dwarf planets do not have this distinction. And yet these objects are significantly heavier than mere asteroids, in that they are so heavy that their own weight, and more particularly their own gravity, forces them to assume the round or nearly-round shape that all planets have.
True-color image of
PlutoEris has another distinction that forced the debate: it is more massive even than
Pluto (by twenty-seven percent) and is therefore the heaviest dwarf planet yet found. The mass of Eris is inferred from the orbital parameters, including the
apsides and period, of the small body that orbits Eris. If Pluto could still be called a planet, then Eris deserved that distinction as well.
In 2006, the International Astronomical Union settled the issue. They determined that Eris was not a planet, and neither was Pluto. But the criteria they set also provoked yet another reassessment of the status of Ceres, the largest and first-discovered object in the asteroid belt. Upon consideration, the IAU declared that Ceres was a dwarf planet as well.
Today the list of dwarf planets is limited to these three: Eris, Pluto, and Ceres.
Table
List of all known dwarf planets, from the innermost to the outermost:
References
- ↑ "IAU0602: the Final IAU Resolution on the Definition of 'Planet' Ready for Voting," International Astronomical Union, 2005. Accessed January 14, 2008.
