Moreover now Pluto is definied as "dwarf planet", head of the new category of "Plutonids".
Well, IMHO from bad to worse.
Anyhow, this is the new IAU resolution, that almost surely will be approved next Thursday:
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IAU Resolution: Definition of a Planet in the Solar System*
Contemporary observations are changing our understanding od planetary systems, and it is important that our nomenclature for objects reflect our current understanding. This applies, in particular, to the designation 'planets'. The word 'planet' originally described as 'wanderers' that were known only as moving lights in the sky. Recent discoveries lead us to create a new definition, which we can make using currently available scientific information.
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RESOLUTION 5 (draft c)*
The IAU therefore resolves that planets and other bodies in our Solar System be defined into three distinct categories in the following way:
1) A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape (NOTE: An IAU process will be established to assign borderline objects into either dwarf-planet and other categories), (b) is the dominant object in its local population zone, and (c) is in orbit around the Sun.
2) A dwarf-planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape (NOTE: An IAU process will be established to assign borderline objects into either dwarf-planet and other categories) and (b) is in orbit around the Sun.
3) All other objects orbiting the Sun, currently including most of the Solar System asteroids, near-Earth objects (NEOs), Mars-, Jupiter-, Neptune- Trojan asteroids, most Centaurs, most Trans-Neptunian Objects (TNOs), and comets, shall be referred to collectively as "Small Solar System Bodies". In the new nomenclature the term "minor planet" is not used.
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RESOLUTION 6 (draft c)
*The IAU further resolves:
Pluto is a dwarf-planet by the above definition, as are one or more recently discovered large trans-Neptunian objects. Dwarf-planets that have orbital periods in excess of 200years and typically have highly inclined orbits with large eccentricity are designated category of planetary objects, of which Pluto is the prototype, as a new class that we call 'plutonids'.
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Well, astronomy is even this, sometimes.
Bye
Andrea