[ExI] ligo again: was: RE: puzzling

John Clark johnkclark at gmail.com
Thu Oct 22 14:33:30 UTC 2020

On Wed, Oct 21, 2020 at 11:06 PM Stuart LaForge via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

* > Direct collapse would still heat up the gas igniting fusion which would
> exert pressure and thereby counteract collapse.*

Not necessarily, the gas cloud could reach the Schwarzschild radius before
it got hot enough to ignite fusion and start to drive the gas away, but
calculations show that for such a thing to happen the initial conditions
before the collapse must be arranged in a very specific way and that means
it would be quite rare. However such calculations largely ignore Dark
Matter so, because there is five times as much of that than there is normal
matter, I take such calculations with a grain of salt.

> *>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?*

A 100 solar mass star would only produce about a 35 solar mass black hole
because most of the star's mass would be blasted away into space long
before the black hole formed. And a low metallicity 130 to 250 solar mass
star would end its life in a Pair-Instability Supernova, the most intense
type, and they are so powerful they blow themselves apart completely and
leave nothing behind, not a Neutron Star not a Black Hole, nothing.

> *> 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.*

There are examples of stars of more than 250 solar masses that never go
supernova at all they just suddenly seem to turn themselves off, but such
examples are very rare and even stars with zero metallicity would be
unstable if they got much larger than 300 solar masses, or at least they
would if you ignore dark matter. There is a suggestion that in the early
universe dark matter was more concentrated than it is now so if a star was
composed mainly from ordinary matter but if just 0.1% of it was made of
Neutralinos, a WIMP that is its own antiparticle, the resulting
annihilation would provide enough energy to keep a star of up to 10 million
solar masses stable. But nobody has ever seen such a thing and since the
proposal was made people have looked for Neutralinos but found nothing, it's
starting to seem that whatever dark matter is it's not Neutralinos or even
made of WIMPs.

Dark Matter and the First Stars: A New Phase of Stellar Evolution

> * > Perhaps dark matter is composed of both WIMPs and MACHOs. *

As far as a black hole is concerned the details about what the matter that
is forming it is composed of is a relevant, all it cares about is its mass
it's electrical charge and the amount of spin it can impose.

John K Clark
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