A quasistar is a hypothetical type of extremely massive
starthat may have existed very early in the history of the Universe. Unlike modern stars, which are powered by nuclear fusion in their cores, a quasistar's energy would come from material falling into a central black hole.cite news| url=http://space.newscientist.com/article/dn12982-biggest-black-holes-may-grow-inside-quasistars.html| title= Biggest black holes may grow inside 'quasistars'| date=29 November, 2007| publisher=NewScientist.com news service| first= Stephen| last= Battersby]
A quasistar is predicted to form when the core of a large
protostarcollapses into a black hole during its formation and the outer layers of the star are massive enough to absorb the resulting burst of energy without being blown away (as they are with modern supernovas). Such a star would have to be at least one thousand times the mass of the Sun. Stars this large could only form early in the history of the Universe before the hydrogen and helium were contaminated by heavier elements; see Population IIIstars.
Once the black hole had formed at the core of the protostar, it would continue generating a large amount of radiant energy from the infall of additional stellar material. This energy would counteract the force of the black hole's gravity, creating an equilibrium similar to the one that supports modern fusion-based stars.cite journal| url=http://arxiv.org/abs/0711.4078| title= Quasistars: Accreting black holes inside massive envelopes| date=16th April, 2008| publisher=arXiv preprint server| first= Mitchell| last= Begelman| coauthors =
Rossi, Elena; Armitage, Philip] A quasistar is predicted to have had a maximum lifespan of about one million years, after which the core black hole would have grown to about ten thousand solar masses. These intermediate mass black holes have been suggested as the origin of the modern era's supermassive black holes. Quasistars are predicted to have a surface temperature comparable to that of the Sun, but with a diameter of approximately ten billion kilometers each one would produce as much light as a small galaxy.
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