[ExI] ligo again: was: RE: puzzling

[Stuart LaForge]

Quoting John Clark:

> It's difficult for a small Black Hole to grow into a large one in the
> limited time available by that method because as matter starts to spiral
> into the hole it gets very hot and produces a lot of x-rays that push much
> of the remaining gas away. Maybe in the very early universe it is formed by
> direct collapse from a cloud of gas to a Black Hole without ever becoming a
> star or even getting very hot because in some ways it's easier to make a
> large Black Hole than a small one because, although you need more matter,
> you don't have to concentrate it as densely to make a large black hole as
> you do to make a small one.

Direct collapse would still heat up the gas igniting fusion which  
would exert pressure and thereby counteract collapse. Is there any  
reason why astronomers don't think these middling 100 solar mass black  
holes aren't collapsed remnants of type III first generation  
zero-metalicity super-giants? They are rumored to have been several  
hundred to several thousand solar masses and went super-nova  
relatively quickly and early in the history of time.

> For example if you wanted to make a one solar
> mass Black Hole you'd have to concentrate matter so it had a density
> 1.8*10^16 times greater than water and have a radius of 3 km, but if you
> wanted to make a 11 billion solar mass Black Hole you'd only need to
> concentrate matter so it had the density of air at sea level, it would then
> have a radius 2 1/2 times that of Pluto's orbit and form a Supermassive
> Black Hole.

Yes and it is inexplicably bizarre that at the critical density of a  
flat infinitely expanding universe predicted by Friedmann, a black  
hole would be formed that had a Schwarzschild radius exactly equal to  
the Hubble radius.

> But I have a hunch we're not gonna really understand how they formed until
> we know what dark matter is, after all there's five times as much of it as
> there is normal matter so it must play a part in the formation of a black
> hole.

Perhaps dark matter is composed of both WIMPs and MACHOs. LIGO is  
showing black holes are far more common than we thought and they could  
comprise a good fraction of the total mass of our local bubble  
universe. It seems to me that the arms of spiral galaxies rotate at  
the same rate as the central disk because they are shepherded by  
LIGO-detectable massed black holes, like Saturn's rings are shepherded  
by moons.

Stuart LaForge