What is the biggest Star in the known Universe....

[Couerl]

Thanks for clarifying, 40 solar masses perhaps is the suggested minimum for a BH then.

 

[crazyeddie]

Thanks for clarifying, 40 solar masses perhaps is the suggested minimum for a BH then.

I don't think that's right. I've always read that the minimum stellar mass remnant in order for an object to become a black hole is only 1.5 times that of the sun.

 

[Saiph]

here's the gist of things:

What you get depends on the size of the star, the inner dynamics, and the core.

For small stars you end up with the star swelling to red giant phase, sloughing the outer atmosphere, and exposing the core, which is a white dwarf. This happens for stars ~7 solar masses or smaller (IIRC)

If the core is larger than 1.5 solar masses (the figure you're thinking CE), which will happen in large stars (up to ~40 solar masses) the core collapses into a neutron star, triggering a supernova explosion. The neutron star can't exceed 3.5 solar masses however.

Stars that are even larger, have their cores collapse into BH's, triggering the supernova explosion. BH's have no upper mass limit.

The confusion that seems to be arising here is the difference between the maximum mass of the remnant, and the mass of the living star required to create said remnant. You have to keep the two clear and seperate

 

[ramparts]

As several people have said, stars of hundreds of solar masses can exist - they just won't live very long, and are going to blow off a lot of mass and generally be very active. One interesting thing is that the first generation of stars (Population III stars), not too long after the Big Bang, were likely on the whole much more massive - up to 1000 solar masses, even - since the only elements going into them in any noticeable quantities were hydrogen and helium. It was in the cores of those stars that large amounts of heavier elements were fused for the first time, and the new stars with higher metallicities are more difficult to get to those high masses.

 

[Couerl]

Thanks for clarifying, 40 solar masses perhaps is the suggested minimum for a BH then.

I don't think that's right. I've always read that the minimum stellar mass remnant in order for an object to become a black hole is only 1.5 times that of the sun.

Right, right.. I misspoke again. What I'm actually curious about is the mass limit any given star can posess/achieve before gravity overtakes fusion and causes an immediate collapse. A situation where a super massive star forms, fusion begins and then gravity simply snuffs it back out from the get go to form a BH.

 

[csmyth3025]

Right, right.. I misspoke again. What I'm actually curious about is the mass limit any given star can posess/achieve before gravity overtakes fusion and causes an immediate collapse. A situation where a super massive star forms, fusion begins and then gravity simply snuffs it back out from the get go to form a BH.

Your question about how large a protostar can grow before the inward force of gravity causes it to collapse directly into a black hole despite the outward pressure of the fusion reactions occurring at its center may be unanswerable. The reason is that there is a theoretical limit (the Eddington Limit) beyond which a star in the process of formation is thought to blow itself apart - or at least shed large amounts of mass. The Wikipedia article entitled "List of Most Massive Stars" can be found here:

http://en.wikipedia.org/wiki/List_of_most_massive_stars

An excerpt from this article explains:

Astronomers have long theorized that as a protostar grows to a size beyond 120 solar masses, something drastic must happen. Although the limit can be stretched for very early Population III stars, if any stars existed above 120 solar mass, they would challenge current theories of stellar evolution.

The limit on mass arises because stars of greater mass have a higher rate of core energy generation, which is higher far out of proportion to their greater mass. For a sufficiently massive star, the outward pressure of radiant energy generated by nuclear fusion in the star’s core exceeds the inward pull of its own gravity. This is called the Eddington limit. Beyond this limit, a star ought to push itself apart, or at least shed enough mass to reduce its internal energy generation to a lower, maintainable rate. In theory, a more massive star could not hold itself together, because of the mass loss resulting from the outflow of stellar material.

Since at least one star ( R136a1) is estimated to be about 265 solar masses, the Eddington Limit cited above is obviously in need of revision.

It seems, though, that the chances of a protostar becoming so massive that it collapses directly to a black hole are slim-to-none.

Chris