Planetary Definition Resolution
The IAU proposal on the definition of a planet has been released from embargo. Simplifying the technical language, the new definition of a planet proposed is:
1. If the body did not rotate, it would be spherical and would tend toward being spherical if seriously perturbed by impact. (In hydrostatic equilibrium or gravitational relaxation).
2. It is not the satellite of a non-stellar body.
Space Daily claims that the additional planets immediately comprehended by this definition according to present knowledge are:
1 Ceres (the largest of the asteroids)
Charon (Pluto's "moon", which apparently is so large that the center of gravity of the Pluto-Charon system is outside of the body of Pluto), making Charon technically a satellite of the Sun.
2003UB313: Mike Brown's new planet
I am fairly sure that 4 Vesta also fits this new definition, because its oblate shape is only due to its swift rotation. It is also thought to be in hydrostatic equilibrium.
According to this definition, no canonical planets would lose status. There is no word from the International Astrological Union about what they think about this.
The definition will be considered and voted upon by delegates to the IAU meeting presently being held in Prague.
ESA(20060815.1)
The IAU proposal on the definition of a planet has been released from embargo. Simplifying the technical language, the new definition of a planet proposed is:
1. If the body did not rotate, it would be spherical and would tend toward being spherical if seriously perturbed by impact. (In hydrostatic equilibrium or gravitational relaxation).
2. It is not the satellite of a non-stellar body.
Space Daily claims that the additional planets immediately comprehended by this definition according to present knowledge are:
1 Ceres (the largest of the asteroids)
Charon (Pluto's "moon", which apparently is so large that the center of gravity of the Pluto-Charon system is outside of the body of Pluto), making Charon technically a satellite of the Sun.
2003UB313: Mike Brown's new planet
I am fairly sure that 4 Vesta also fits this new definition, because its oblate shape is only due to its swift rotation. It is also thought to be in hydrostatic equilibrium.
According to this definition, no canonical planets would lose status. There is no word from the International Astrological Union about what they think about this.
The definition will be considered and voted upon by delegates to the IAU meeting presently being held in Prague.
ESA(20060815.1)
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