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Some stars are simply huge. Eventually, though, wouldn't there be simply too much pressure or mass for the star to sustain itself? Wouldn't it eventually collapse into a black hole?

Is there a theoretical upper limit on the size of a star, and what is it based on?

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up vote 10 down vote accepted

According to current knowledge, yes. If the gas cloud is too massive, the pressure of the radiation prevents the collapse and the star formation.

The article Stars Have a Size Limit by Michael Schirber, it's about 150 Solar Masses. However, there's the Pistol Star, which is speculated to be 200 SM.

In the article 'Das wechselhafte Leben der Sterne' by Ralf Launhard (Spektrum 8/2013) there's a diagram with information that when the mass is over 100 SM, the star can't form because of radiation pressure. The exact value of the limit is not speculated in the article.

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@Undo Adding 2 more cents to this already superb answer: R136a1, has a mass of 265 solar masses and is currently considered to be at the limit of how big stars can become . Btw: it is assumed R136a1 once had 320 solar masses when it was born a million or so years ago. – e-sushi Oct 11 '13 at 1:19

The first order theoretical limit on stellar size is from the Eddington Limit. As the star collapses it is balances by radiation pressure from fusion. However, the fusion rate scales strongly with density (which is why the most massive stars have extremely short lifetime) so if the star was massive enough, the radiation pressure would probably blow it apart. In fact, this could lead to a pair-instability supernova and there wouldn't even be a black hole remnant even though the star is so massive.

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