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What would the properties of a star formed from a sphere a water/ice be? One large (massive) enough to collapse into an ordinary, mostly plasma star.

I understand that it would have particularly high levels of oxygen.

Qmechanic
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alan2here
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    The question is sort of invalid, actually :) You can't have a star made up of water. Stars aren't made up of molecules, they're made up of plasma. – Hritik Narayan May 13 '15 at 11:49
  • This is true, but apparently with one formed from water, I'll quote from http://physics.stackexchange.com/q/183527/ – alan2here May 13 '15 at 12:32
  • If the gravitational collapse mentioned in that question does happen, the water wouldn't remain water for long! – Hritik Narayan May 13 '15 at 12:34
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    "Basically, if you had a ball of ice with the mass of sun, it would very quickly turn into a sun. A rather odd sun, to be sure (at least if you're an astrophysicist), because of the absurdly high oxygen content, but a sun nonetheless.", "the water molecules that make up the ice would break up into a plasma of free oxygen and hydrogen atoms" – alan2here May 13 '15 at 12:36
  • Yes, I'm confused now about this too, your correct, I too thought that plasma is a soup of sub-atmoic particles. – alan2here May 13 '15 at 12:38
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    @Alan2here It is, if you're talking about a hydrogen plasma and define "atoms" to be strictly neutral, as opposed to ions - and given that most the mass of most stars is hydrogen plasma, the confusion is understandable. – Asher May 13 '15 at 16:10
  • Please feel free to edit the question to use the correct terminology, I'm not sure how to express it. – alan2here May 20 '15 at 13:02
  • This would fit well on worldbuilding.SE thought. – Tomáš Zato Mar 14 '16 at 09:59
  • See https://astronomy.stackexchange.com/questions/20448/how-large-can-a-ball-of-water-be-without-fusion-starting for an answer – ProfRob Nov 18 '20 at 16:46

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From the question you've linked to, I assume you're asking what would happen if a dense and insanely huge water/ice body was to undergo strong gravitational collapse. Stars are made up of Plasma, and Plasma is extremely high energy stuff. The pressure energy density on the molecules during the gravitational collapse process is more than enough to rip molecules apart and turn them into plasma made up of their constituent atoms. Water, in this case, would split up into Hydrogen and Oxygen. The only thing different about this star would be the rate and efficiency of its fusion process, because of its strange Oxygen to Hydrogen ratio. Whether this process is normal or not would depend on the mass of the star.

Hritik Narayan
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  • The increased efficiency of this process making the star longer lived than most? – alan2here May 13 '15 at 15:25
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    Its not necessary that there would be an efficiency increase. If there was, the star would 'burn out its fuel' faster, and would have a shorter life. – Hritik Narayan May 13 '15 at 15:28
  • In this case being very bright then too I imagine. – alan2here May 13 '15 at 15:41
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    Yes, the rate would be completely different and the mass of the "star" could be much lower. https://physics.stackexchange.com/questions/407719/minimum-size-of-a-water-star?rq=1 – ProfRob Nov 18 '20 at 16:48