I have a basic understanding of how gaseous bodies behave according to their mass:

  • "Low mass" bodies are gas giants (or brown dwarfs),
  • Beyond a certain mass, hydrogen fusion starts, making a star,
  • More massive bodies burn shinier and faster,
  • Beyond a certain mass, even the thermonuclear fusion can't prevent the collapse into a black hole.

I don't know if there is a stage between the last two, only depending on initial mass (not talking about star evolution, when they burn their fuel)

But, how would a very massive rocky body behave?

  • I guess that a rocky body of a solar mass wouldn't become a star, because its heavy compounds couldn't fusion at such pressures,

  • I also guess that at some mass (not necessarily the same for the stars), it would collapse into a black hole.

Are these guesses true? Would there be an intermediary stage between the two (a star like form, or otherwise)? Or, would such a body be somehow impossible/unstable?

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    $\begingroup$ Do you mean "rocky body" as in meteors or asteroids or rocky planets? And are you asking about their formation/evolution? $\endgroup$
    – Kyle Kanos
    Commented Jan 3, 2015 at 21:44
  • $\begingroup$ @KyleKanos I'm talking about hypotheticals rocky bodies, much more heavier than planets. I'm neither asking about their formation or evolution (they're probably not even existing in our universe), but how would they would look if they had mass between what is needed for a star and a black hole to form. Basically, if a rocky body with enough mass could become some sort of star or other thing, before collapsing into a black hole. $\endgroup$
    – OxTaz
    Commented Jan 3, 2015 at 22:04
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    $\begingroup$ How would they form? They'd have enough mass to coalesce the surrounding gas too so they'd have at atmosphere. You'd end up with something like Jupiter. $\endgroup$ Commented Jan 3, 2015 at 22:11
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    $\begingroup$ It's unclear to me what you're imagining. Clearly, a massive rocky body can't suddenly pop into existence but must form and evolve over time. So, what are the initial conditions are you imagining? $\endgroup$ Commented Jan 3, 2015 at 23:48

1 Answer 1


If you put a lot of rocky planets together they will result in either a neutron star or a black, depending on the mass. The reason is that there is not much fuel left to fight against a gravitational collapse. For instance, the mass limit to make a black hole is a function of the mass, not of the composition. More or less the same for a neutron star. Below those masses the object will stay rocky, but depending how it is formed, it might remain very hot for a long time.


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