[ExI] ligo again: was: RE: puzzling

[Stuart LaForge]

Quoting John Clark:


> 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.

Blind faith in dark matter particles could be what is causing the  
Hubble telescope and the Planck satellite to disagree on the value of  
Hubble's not-so-constant.


>
>> *>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.

Pair-production instability is pretty wild. I learned something new. Thanks.

>
>
>> *> 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.

If it isn't WIMPs it is almost certainly black holes.

> 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.

It is a very interesting coincidence that the radial density of the  
Milky Way that supports a uniform orbital rotation rate of 250 km/sec  
(1) is a constant 3.6 million solar masses per light year. 3.6 million  
solar masses happens to be the estimated mass of Sagittarius A*, the  
Milky Way's axis mundi. The stars and nebulae of the Milky Way form a  
ring system around Sagittarius A* that is shepherded by satellite  
black holes of middling masses perhaps spawned as you say near the  
dawn of time by direct collapse of population III stars or primordial
gas collapse.

Stuart LaForge

(1) http://ogle.astrouw.edu.pl/cont/4_main/str/rotat_curv/