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Old December 12th 17, 10:01 PM posted to sci.astro.research
Martin Brown[_3_]
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Default A quasar, too heavy to be true

On 10/12/2017 21:29, jacobnavia wrote:
https://www.nature.com/articles/nature25180

[[Mod. note -- Open-access preprint at
https://arxiv.org/abs/1712.01860
-- jt]]

Here we report observations of the quasar ULAS J134208.10+092838.61
(hereafter J1342+0928) at a redshift of z=7.54. This quasar has a
bolometric luminosity of 4e13 Lsun and a black hole mass of 8e8 Msun.

Wow!

https://www.sciencedaily.com/release...1206131946.htm
"This is the only object we have observed from this era," says Robert
Simcoe, the Francis L. Friedman Professor of Physics in MIT's Kavli
Institute for Astrophysics and Space Research. "It has an extremely high
mass, and yet the universe is so young that this thing shouldn't exist.
The universe was just not old enough to make a black hole that big. It's
very puzzling."

Exactly. It is at 690 My after the supposed "bang".

Of course there is an explanation. The authors of the nature paper say
that the big bang created black holes and the problem is solved: The big
pre-existing black holes of the universe (with 10E4 solar masses) would
have seeded this thing of course.


You wouldn't need very many such seeds to meet the observational
constraints. Only one other quasar is known at that sort of redshift.
There may be others but we will only be able to see the very brightest
ones or those that by sheer luck are gravitationally lensed.

How can gravity influence things in the searing hot universe coming from
a big bang???


Gravity influences things right from the very start. It doesn't really
have much of a bite until things cool to below 4000K and Z~1000 in the
recombination era and there is a decent proportion of transparent
neutral hydrogen gas with photons able to travel freely some distance.

There is a very large gap between Z=7.5 (this quasar) and Z=1000.

Before a certain point, not even light can travel isn't it?


The universe is opaque until the universe cools to allow neutral
hydrogen when it becomes transparent. Later during the star formation
era it is partially re-ionised by the UV from the first stars. It looks
like this quasar is far enough away that its light has to pass through
some of this newly reionised material which makes it an interesting
probe into the early universe. Absorption spectra will show one heck of
a Lyman forest and other interesting features.

Before the decoupling?

How can gravity influence anything at those temperatures?


It is always an attractive force.

Mystery. Well anyway, the universe can do anything so let's suppose that.

Why not see otherwise that there wasn't any bang at all and that we are
seeing a very old quasar?


Quasars and radio galaxies are intrinsically quite young. The huge
numbers of them at moderate redshifts and shortage of them nearby was
one of the things that killed the Steady State theories stone dead.

The spectra correspond to a quasar. The simplest explanation is that
this IS a quasar, a very old one.


It was very young when the light left it. Very young indeed. It is
possible that it is Kerr metric feeding at its optimum rate and we are
looking at it from the most favourable possible angle to see it at all.
This implies that the universe must be at least 20-30 Gy old.


It implies nothing of the sort.

--
Regards,
Martin Brown