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by hibbelig 2742 days ago
Well, Farout orbits the sun, is round, is not a moon. The article is silent on item d.

I don't know what to do with the information that its diameter is 500km. I guess that makes it 1/5 of Pluto's diameter, and given that Pluto is called a dwarf planet...
3 comments
zamadatix 2741 days ago
"round" is a bit oversimplified in the above the actual criteria is:

"(b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, "

If Farout is highly icy 500km could be enough to qualify it.

Regardless it isn't nearly massive enough to clear it's orbit.

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jessriedel 2741 days ago
> The article is silent on item d.

I believe the mass and orbital parameters necessary to clear an orbit of debris are known pretty well known theoretically, and farout won't satisfy it. This is why astronomers can "be looking for Planet 9/X/10" without searching for debris everywhere. (Likewise, knowing the rough mass is enough to know whether a body has a hydrostatic shape; you don't have to actually resolve it's shape in your telescope.)

Edit: yep: https://en.wikipedia.org/wiki/Clearing_the_neighbourhood#Cri...

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walrus01 2742 days ago
500 km is about the size of one of the bigger asteroid belt objects:

https://en.wikipedia.org/wiki/4_Vesta

Notably, Ceres is about 950km and much more spherical.

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