As I get along with the answers in my previous question, that planet formation depends on accumulation of planetesimals. So is there any chance that a planet nine would form or any of the Trans-Neptunian Object, "evolve" into a planet in or near the Kuiper Belt, which is thought to be a belt of planetesimals?

Although we don't know fully about the Kuiper belt, what can we conclude from the information and models we have now.


  • 4
    $\begingroup$ As far as we know, there's not a lot of matter in the Kuiper belt, and it's mostly spread very thinly. Bear in mind that our Moon is almost 6 times heavier than Pluto. OTOH, it was kinda surprising when we discovered several largish trans-Neptunian bodies, so there could be more stuff hiding out there in the dark. $\endgroup$
    – PM 2Ring
    Commented Jan 25, 2022 at 15:42
  • $\begingroup$ @PM2Ring I agree ! $\endgroup$ Commented Jan 25, 2022 at 16:03
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    $\begingroup$ The largest TNOs are still dwarf planets. Search for 'hypothetical ninth planet' here to have a more insight. $\endgroup$ Commented Jan 26, 2022 at 5:23
  • $\begingroup$ Do not assume the planets of our solar system have always occupied the orbits they current have. Years ago I came across information that mentioned that Jupiter was once closer to the Sun & it moved to its current orbit. If the mysterious ninth planet exists it might have formed closer in & got flung out to a more distance orbit. $\endgroup$
    – Fred
    Commented Jan 26, 2022 at 23:23
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    $\begingroup$ The question specifies formation in the Kuiper belt. $\endgroup$
    – ProfRob
    Commented Jan 27, 2022 at 0:04


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