Was the core of a galaxy once a mega massive star?

[Pakmoto]

OK allow me to try and explain what I'm talking about

Slightly simplified, after the big bang came mega massive stars (now cores of galaxies)

Then the mega massive stars ended their life's creating super massive black holes and mega massive nebula (galaxy size)

Then from the mega massive nebula came many more smaller stars (galaxies)

Am I anywhere near or way off the mark?

[jinstan]

It is generally accepted that there is a black hole in the centre of a galaxy. But how does it form seems to be open.

Current theories don't support the SN of massive stars produce smaller starts IMHO.

[brianb]

Slightly simplified, after the big bang came mega massive stars (now cores of galaxies)

Then the mega massive stars ended their life's creating super massive black holes and mega massive nebula (galaxy size)

Then from the mega massive nebula came many more smaller stars (galaxies)

Am I anywhere near or way off the mark?

There is a real issue with making supermassive stars - the radiation pressure from the forming star tends to blow away the outer layers of the material which is still infalling - in the early universe the infalling material would have been quite transparent optically (until heated to ~7000 K) allowing massive stars to form more easily than they do now that the material contains significant amounts of dust grains etc. but nevertheless there is no known means whereby a star exceeding a mass of ~200 solar masses can form, except by very rare events where protostars collide with each other & merge. Stars in the 100 solar mass range which go supernova will produce a black hole with a relatively small mass (a few solar masses) or even just a neutron star core as a remnant.

OTOH there are mechanisms whereby black holes with essentially unlimited masses can be formed in the very early universe, just a very small fraction of a second after the big bang (before gravitation seperated out from the other forces). One difficulty with the theory is the lack of permeation of the universe with lightweight (planet mass) black holes ... we don't know everything yet!

[Ben Ritchie]

but nevertheless there is no known means whereby a star exceeding a mass of ~200 solar masses can form

Not sure that's true, e.g. R136a1

ESO - eso1030 - Stars Just Got Bigger

(if you read the full paper then two other stars in the cluster are also thought to have initial masses above 200 solar). The truncated IMF at 150 solar masses idea (e.g. from Figer's work on the Arches cluster) is now considered to be more statistical than anything else

[Pakmoto]

Thanks for putting me right

Since posting this thread I read a little about dark stars and how they may have been the first stars in the early universe, do you feel this is related to my question?

Did Dark Matter Power Early Stars?

[brianb]

e.g. R136a1

There have been a few issues like this raised. Previously they've been "answered" by a recalculation of the distance of the star, or the discovery that what was thought to be a single supermassive star has turned out to be a pair of very massive stars. I don't think the derived mass of R136a1 is as accurate as the article suggests. The physics of radiation pressure on low density gases at moderate temperatures is however very well known and it's that which determines the maximum mass that can be accreted as a single body.

[brianb]

I read a little about dark stars and how they may have been the first stars in the early universe, do you feel this is related to my question?

Yes, it's definitely related - but whether the theory holds water or not depends on dark matter being (mostly) composed of WIMPs, and the WIMPs themselves are theoretical objects rather than things that have experimentally verifiable properties. There's as much experimental evidence for the dark matter being unicorn poo as there is for it being composed of WIMPs. Now I fully accept that WIMPs are rather more likely to account for dark matter than unicorn poo is, but I think you'll get my drift.

[AirborneAnt]

On March 15, 2011 at 16:38, Pakmoto said:

OK allow me to try and explain what I'm talking about

Slightly simplified, after the big bang came mega massive stars (now cores of galaxies)

Then the mega massive stars ended their life's creating super massive black holes and mega massive nebula (galaxy size)

Then from the mega massive nebula came many more smaller stars (galaxies)

Am I anywhere near or way off the mark?

I 100% agree with you, it seems the Galaxy was once one massisive mega star, it underwent a supermassive supernova, left a supermassive blackhole, and all the debris paved the way for other new stars to form and they continue the process, and wa la! We have a galaxy  

[andrew s]

This gives some views on the possible origins of the galactic BH https://en.wikipedia.org/wiki/Supermassive_black_hole#Formation

Regards Andrew