On 4/9/2018 6:27 AM, jacobnavia wrote:
Le 08/04/2018 à 22:16, Phillip Helbig (undress to reply) a écrit :
In article , jacobnavia
writes:

Heavy stars are produced by the galaxy, converting cold gas into black
holes or heavy neutron stars.

Supernova explosions aren't symmetric, most stars receive a "kick" when
transforming into a black hole or a neutron star.

As eons pass, the dead stars accumulate either at the center of the
galaxy or in a diffuse halo of invisible matter around the galaxy.

This invisible mass can't explain the sorely needed black matter?

No, since it would mean a baryonic density higher than that obtained by
other arguments.

Yes, of course that would mean a higher baryon density... Black holes
and small cool white dwarfs are undetectable by most scopes.

That may be a non sequitur. Black holes could be primordial, stemming
from a time long before baryogenesis (well, not too long of course..)
So their existence is not ruled out by any baryon-related argument.
And also detectability is not the key point here, the amount of
baryonic matter that we expect to be created after the big bang is
simply much lower than what you would need.

[[Mod. note --
We are quite confident that some supernovae produce black holes,
so at least some black holes are non-primordial.
-- jt]]

....
An hitherto unknown population of black holes near the center has been
discovered. Halo black holes are MUCH more difficult to detect,

But they would not likely be remnants of stars (those would be inside
the galaxy). So we are back at non-baryonic matter. And of course there
are many exellent reasons why we should *expect* a lot of non-barionic
matter. To give just three:
1) Primordial black holes might exist. In the range of several tens
of solar masses they might as of yet be undetected.
2) The strong CP problem requires the axion to exist, or some other
new physics, and with an axion of, say, 100ueV you are there!
3) There are reasons to expect heavy, sterile neutrinos to exist.

Each of those could by itself explain dark matter. Perhaps we'll soon
be facing the problem of too much of it. You know how things change!

--
Jos