A discussion on "officially called a planet"

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Forking a subject that was in risk of hi-jacking anther thread here.

If the hypothetical TNO "planet 9" is detected , it would not fit the IAU's current criteria of being a planet. What would it be ?

For the sake of discussion let's assume 10 Me and estimated likely distance and orbital period.

Would it fit an existing category or would it require a new term or another redefinition of what a "planet" is?
 

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  • #2
phyzguy
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A really big TNO(Trans-Neptunian Object)?
 
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  • #3
russ_watters
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Current definition:
  • orbits the sun
  • has sufficient mass to be round, or nearly round
  • is not a satellite (moon) of another object
  • has removed debris and small objects from the area around its orbit
https://www.space.com/25986-planet-definition.html

A more specific take on the 4th criteria is that it has a mass greater than the combined mass of all objects in a similar orbit.

Given the distance, I think such objects tend to have eccentric orbits and trouble clearing them. Thus I don't think they can be classified as planets.
 
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Yes , the orbit clearing thing is what caught Plluto out, but a 10Me it cant be called a dwarf planet; neither is it a rogue if it is orbiting.

It's planet sized but not a planet. Will we need to move the goalposts again?
 
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