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Line 57: − + − + − (2) A "[[dwarf planet]]" is a celestial body that (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<sup>2</sup>, (c) has not cleared the neighbourhood around its orbit, and (d)is not a satellite.+ − + + + + + + + + + − <sup>1</sup>The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. − + + + + + + + + + + Line 76:
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→The dwarf planet controversy: Edited quote and added reference and section heading
The discovery of [[Eris]], a scatter-disk body 27% more massive than Pluto, caused a controversy concerning what does, and what does not, constitute a [[planet]]. If Pluto were to retain its historical designation of "planet," then Eris would also qualify. But Eris was held not to qualify because it was in a neighborhood with multiple other objects, a situation similar to those of similar bodies in the [[asteroid]] belt, namely [[Ceres]] and [[Eris]].
The discovery of [[Eris]], a scatter-disk body 27% more massive than Pluto, caused a controversy concerning what does, and what does not, constitute a [[planet]]. If Pluto were to retain its historical designation of "planet," then Eris would also qualify. But Eris was held not to qualify because it was in a neighborhood with multiple other objects, a situation similar to those of similar bodies in the [[asteroid]] belt, namely [[Ceres]] and [[Eris]].
In 2006, the [[International Astronomical Union]] passed the following resolution:{{cquote|'''RESOLUTION 5A'''
In 2006, the [[International Astronomical Union]] passed the following resolution:{{Quotebox|'''RESOLUTION 5A'''
The IAU therefore resolves that planets and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way:
The IAU therefore resolves that planets and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way:
(1) A "planet"<sup>1</sup> is a celestial body that (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, and (c) has cleared the neighbourhood around its orbit.
* (1) A "planet"<sup>1</sup> is a celestial body that
* (a) is in orbit around the Sun,
(3) All other objects<sup>3</sup>, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".
* (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
* (c) has cleared the neighborhood around its orbit.
* (2) A "[[dwarf planet]]" is a celestial body that **(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<sup>2</sup>, **(c) has not cleared the neighborhood around its orbit, and **(d)is not a satellite.
* (3) All other objects<sup>3</sup>, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".
<sup>1</sup>''The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.''
<sup>2</sup>An IAU process will be established to assign borderline objects into either dwarf planet and other categories.
<sup>2</sup>An IAU process will be established to assign borderline objects into either dwarf planet and other categories.
<sup>3</sup>These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.<ref>"[http://www.iau.org/iau0602.423.0.html IAU0602: the Final IAU Resolution on the Definition of 'Planet' Ready for Voting]," ''International Astronomical Union'', 2005. Accessed January 14, 2008.</ref> }}
<sup>3</sup>These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.
The IAU further resolves:
* '''''Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of Trans-Neptunian Objects''''' <sup>1</sup>.
<sup>1</sup> An IAU process will be established to select a name for this category.
— ''International Astronomical Union''}}<ref>"[http://www.iau.org/iau0602.423.0.html IAU0602: the Final IAU Resolution on the Definition of 'Planet' Ready for Voting]," ''International Astronomical Union'', 2005. Accessed January 14, 2008.</ref><ref>https://www.iau.org/static/resolutions/Resolution_GA26-5-6.pdf ''International Astronomical Union'', 2005. Accessed February 9, 2022</ref>
Under those rather strict criteria, Pluto does not qualify. For that reason, Pluto is no longer considered a planet. It shares the new "dwarf planet" category with Eris, Ceres, Haumea and Makemake.<ref>http://www.iau.org/public_press/news/detail/iau0807/</ref>
Under those rather strict criteria, Pluto does not qualify. For that reason, Pluto is no longer considered a planet. It shares the new "dwarf planet" category with Eris, Ceres, Haumea and Makemake.<ref>http://www.iau.org/public_press/news/detail/iau0807/</ref>
Brown suspects the IAU wanted to demote Pluto, because Pluto violates, by its very existence, every conventional theory of planetary origin.
Brown suspects the IAU wanted to demote Pluto, because Pluto violates, by its very existence, every conventional theory of planetary origin.
According to Number 1 (c) and 2 (c) of the IAU definition, also [[Earth]] and [[Mars]] wouldn't be planets because they haven't "cleared" their orbits, but have several asteroids in them, also called "quasi-moons" of Earth and Mars.
=[[Earth]] and [[Mars]] as [[dwarf planet|dwarf planets]] under the current [[International Astronomical Union]] definition=
According to Number 1 (c) and 2 (c) of the [[International Astronomical Union|IAU]] definition, also [[Earth]] and [[Mars]] wouldn't be planets because they haven't "cleared" their orbits as several asteroids are in their respective orbits, these asteroids are also called "quasi-moons" of Earth and Mars. The IAU precluded this possibility by arbitrarily listing the earth and mars as planets in spite of the current definition (see the quote in the above section: ''"<sup>1</sup>The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune."'').
This, however, calls into question the "''scientific''" basis of downgrading Pluto to a dwarf plant as this conflicting standard(of confirming [[earth]] and [[mars]] as planets while classifying Pluto as a dwarf planet) suggests it is merely the '''''opinion''''' of the IAU that Pluto is not a planet <ref>https://www.iau.org/static/resolutions/Resolution_GA26-5-6.pdf ''International Astronomical Union'', 2005. Accessed February 9, 2022</ref>
== Orbital characteristics ==
== Orbital characteristics ==