Thread: Supermassive Black Holes not from massive stars...

I'm not sure if this has been proven or disproven, but here goes anyway...!

I have reason to believe that supermassive black holes in the centre of every galaxy aren't the remnants of a single or a few massive stars.

Why?

Now we all know that stars with a mass from typically 5<m(suns)>18, form neutron stars or pulsars- ultra-dense remnants of stars with a typical density ratio of

1 grain of sand sized piece of Neutron Star: Mass of Manhattan Island.

So stars with a mass of 18<m(suns)>149(?) form black holes due to intense pressure from outer layer matter of the star and the reaction force of outwards expended supernova matter...

Now, I've read many articles that suggest that stars with a mass of >150 of our sun don't become black holes, now I don't know why this is, perhaps someone can explain.

So taking this into account, supermassive black holes cannot have come from a truly massive star as it would've been too massive to become a black hole. The only way a supermassive black hole could've been formed from stars is if there was a large cluster of massive stars (that could turn into black holes) that all 'died out' at around the same time. I'm not sure if there are other more likely explanations for Supermassive black hole formation- I know that for a black hole to form, two masses of mass M must get closer to each other than a distance of 4GM/c^2, I think...

Could someone, or many people, please clarify these topics for me? It would be much appreciated...

Please go easy on me though, don't just say 'nonsense' to everything I've put. I'm only 16 years old and don't have the experience that many of you probably have...

(You may have noticed that in my introduction post a few days ago, it stated that I had a phD etc etc. Obviously this is nonsense, and I didn't put that- it was my brother messing around when I had to go away from my laptop! Sorry...!)

Thanks,

- x(x-y)

AFAIK, there's no such thing as too massive for black holes. Also, as far as I understand current theories, the supermassive black holes at the centers of galaxies formed at the same time as the galaxies, before the stars formed, and so aren't made of stars like normal black holes.

The collapse of a core of a very massive star is only one way to produce a Black Hole. There are others. The massive Black Holes in the centre of galaxies usually have several million solar masses. This figure alone makes it clear that such an object cannot form from a few massive stars alone, unless they are used as the seed for accreting more matter. As fas as I know - please somebody correct me, if you know it better - the Black Holes in the centre of galaxies are formed by accreting interstellar matter (gas and dust) as well as entire stellar clusters. The main differences between stellar and galactic Black Holes are the very different typical time scales and involved densities. A few hints can be found on this wiki page:
http://en.wikipedia.org/wiki/Supermassive_black_hole

Thank you for your contributions, they are appreciated very much!

I am fairly young and love learning new 'stuff' about these kind of topics, they interest me greatly.

Anyway, I'm pretty sure there is a limit to the mass of a star that can form into a black hole- something like 150 solar masses, I think...

Also, scientists are currently looking into the apparent size limit of a star- there should because limit to how large a star can grow...

Originally Posted by [url=http://en.wikipedia.org/wiki/Star#Mass

Wikipedia[/url]]One of the most massive stars known is Eta Carinae, with 100–150 times as much mass as the Sun; its lifespan is very short—only several million years at most. A study of the Arches cluster suggests that 150 solar masses is the upper limit for stars in the current era of the universe. The reason for this limit is not precisely known, but it is partially due to the Eddington luminosity which defines the maximum amount of luminosity that can pass through the atmosphere of a star without ejecting the gases into space. However, a star named R136a1 in the RMC 136a star cluster has been measured at 265 solar masses, putting this limit into question.

Ah right, ok, I get it. Yes, I read somewhere that there should be a limit of 150 solar masses on stars size due to the Eddington Luminosity. However, it doesn't seem that way at all- because of the star you mentioned and another star I've heard of called VY Canis Majoris...

So, let me get this straight. The reason for the supposed limit is because the photons which are ejected from the core have a physical effect upon the other layers of the star, and so they push the other layers out causing gases to be lost rapidly?

Photons have momentum and can push things. At that luminosity, there are enough of them to push gasses up faster than gravity can pull them down, thus blowing them out of the star. That objects exist above that limit suggests that the actual picture is more complicated, as mentioned on the various Wiki pages related to this question.

Originally Posted by MagiMaster

Photons have momentum and can push things. At that luminosity, there are enough of them to push gasses up faster than gravity can pull them down, thus blowing them out of the star. That objects exist above that limit suggests that the actual picture is more complicated, as mentioned on the various Wiki pages related to this question.

Well surely that can be explained by larger stars having a larger gravitational field strength and thus being able to keep the gases in place without photons knocking them out due to momentum? Maybe...

That was already taken into account. (The question is basically meaningless otherwise.)

Originally Posted by x(x-y)

Well surely that can be explained by larger stars having a larger gravitational field strength and thus being able to keep the gases in place without photons knocking them out due to momentum? Maybe...

The mass-luminosity law comes into play here. The luminosity varies by the mass to the power of 3.5. A star twice as massive as our Sun will be 11 times more luminous, and a star 150 times as massive is some 41 million times more luminous. The increase in photon output outpaces the increase in gravity by far.

Originally Posted by Janus

Originally Posted by x(x-y)

Well surely that can be explained by larger stars having a larger gravitational field strength and thus being able to keep the gases in place without photons knocking them out due to momentum? Maybe...

The mass-luminosity law comes into play here. The luminosity varies by the mass to the power or 3.5. A star twice as massive as our Sun will be 11 times more luminous, and a star 150 times as massive is some 41 million times more luminous. The increase in photon output outpaces the increase in gravity by far.

Ah, I see...

Thank you!

Janus:

So if you were to note that in equation form, it would be this?-



Just wondering...

Originally Posted by x(x-y)

Janus:

So if you were to note that in equation form, it would be this?-



Just wondering...

Not exactly, since mass and luminosity are two different properties and cannot be equal to each other. Properly it would be:



where means "is proportional to"

or alternatively:



Where (L1, m1) and (L2,m2) are the respective luminosities and masses of two stars.

Originally Posted by Janus

Originally Posted by x(x-y)

Janus:

So if you were to note that in equation form, it would be this?-



Just wondering...

Not exactly, since mass and luminosity are two different properties and cannot be equal to each other. Properly it would be:



where means "is proportional to"

or alternatively:



Where (L1, m1) and (L2,m2) are the respective luminosities and masses of two stars.

Oh, ok.

I understand now, I should've known that it was proportional to and not equal!