IAU Redefines the Solar System: 12 Planets, Countless Possibilities

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The International Astronomical Union is redefining the Solar System to include 12 planets, with Xena as the most distant and Charon recognized as part of a double planet system with Pluto. Ceres, previously classified as an asteroid, will be designated as the smallest planet. The new definition of a planet emphasizes hydrostatic equilibrium and orbital characteristics, allowing for potential future classifications that could increase the number of recognized planets to hundreds or thousands. This change has sparked debate over the classification of celestial bodies, particularly regarding Pluto's status and the inclusion of other objects like Ceres and Charon. The ongoing discussions highlight the evolving nature of astronomical definitions and their implications for scientific education and public interest.
  • #31
"My Very Educated Mother Just Showed Us Nine Planets", the famous mnemonic to remember the names of the nine planets when we were kids viz. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto.
I wonder what kind new mnemonic has to be invented with the recent developments in the order of planets :biggrin: .
 
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  • #32
Yeah, that is kind of a cop-out, isn't it? I mean, by that definition, Neptune should also be downgraded, because it hasn't cleared Pluto out of its orbit.
 
  • #33
It seems to me they picked a definition where they can call anything a planet or a non-planet, depending on how they "feel" about the object. Really, this whole process was a complete waste of time, and the definition they came up with is downright pathetic.
 
  • #34
Come to think of it, since there are still thousands of NEO's, we don't live on a planet, do we?
 
  • #35
How could there be 12 when they just announced Pluto isn't a planet?
 
  • #36
Line said:
How could there be 12 when they just announced Pluto isn't a planet?

They initially proposed 12 planets, the proposal is then rejected and ended up with demoting pluto instead.
 
  • #37
I'm happy with everything the IAU has done, except "dwarf planets." While Pluto was a planet it had "double status" as a planet and a Kuiper belt object; now it's simply a "dwarf planet" and nothing else. Pluto and Eris (Xena) are clearly just very big Kuiper belt objects, and while I'm happy with the dwarf-planet classification to make them special (Pluto and Eris are special because they're so large and rounded) I think they should also have dual status as dwarf planets and KBOs. They are clearly KBOs and should be recognised as such.
Ceres is an asteroid. Don't tell me it's not. OK, it's special, it deserves to be classed as a dwarf planet because it's large and round, yeah yeah. But... it's clearly an asteroid. Just a big one. How can you possibly say it isn't?
I'd be happy with 8 or 12 planets, as long as Pluto/Eris were recognised as KBOs as well as (dwarf) planets and Ceres was an asteroid as well as a (dwarf) planet.
 

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