A discussion on "officially called a planet"

[fizzy]

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?

 

[phyzguy]

A really big TNO(Trans-Neptunian Object)?

 

[russ_watters]

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.

 

[fizzy]

Yes , the orbit clearing thing is what caught Plluto out, but a 10Me it can't 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?