
A Very Hungry Black Hole Is Found, Gorging on Stars - SREinSF
https://www.nytimes.com/2018/05/17/science/hungry-black-hole.html
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toomanybeersies
Hypothetical question: Would we be able to detect if we were going to get
sucked into a black hole?

~~~
okket
Yes. A black hole is basically a normal star with normal gravity, but you
can't see the gravity source itself. You can detect the motion of all other
stuff around it: Imagine our solar system without the sun visible, the planets
will still move the same (and not get 'sucked in' or 'gobbled up' etc).

Even if there is no stuff moving around the black hole, we still can detect
because the intense gravity bends space and creates lensing effect, which is
easily detectable with modern equipment.

That said, we can infer that it is unlikely that a black hole is in our
galactic vicinity and most certainly not a monster like in this article.
Which, btw, is not only 12 billion light years away, also what we see is 12
billion years ago, putting the whole scene at the beginning of our universe.

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spyckie2
> “How they grew to such mass so early after the Big Bang is a profound puzzle
> for physics,” the authors say in their paper.

Anyone have any details for this tidbit? Would be interested to know more.

~~~
raattgift
This quasi-stellar object (QSO) is so bright that (with some mild assumptions,
including that it's a single supermassive black hole and that its angular
momentum is not super-extremal) its outgoing high-energy photons should
collide with the electrons in star-forming gas and dust anywhere near it,
pushing the electrons outwards from the QSO. In (quasi-)neutral gas, where the
electrons are pushed, they drag their protons with them. If all the electron-
containing matter is pushed away, how do we reconcile that this QSO [a] grew
at all and [b] shines so brightly?

QSOs like this one appear to crash into the Eddington limit, which depends
almost entirely on mass (more below). If we assume a "bottom-up" formation for
this QSO, with early stellar-collapse black holes merging into this
supermassive giant, the problem is that its observed mass is so high that it
and its many smaller progenitor BHs should have blasted away all the star-
forming dust and gas from their neighbourhood. You need a lot of stellar black
holes to merge into this giant, so suppressing star-formation at all is a
problem. Moreover, removing much of the matter from neighbourhood then
mechanisms like dynamic friction fall off, making the black hole merging
process too slow for the relatively short duration (locally to the QSO)
between the epoch early star formation and the QSO as we observe it.

A reasonably accessible 40-slide tutorial on the Eddington limit:

[http://www-astro.physics.ox.ac.uk/~garret/teaching/lecture7-...](http://www-
astro.physics.ox.ac.uk/~garret/teaching/lecture7-2012.pdf)

Note, however, slide 33, which offers up a couple of hints about how the
Eddington limit can be evaded: thick low-density accretion clouds. These are
expected in the "dark ages" of the early universe before there are many stars,
under the standard structure formation model [1].

If we do the hard computing that slide alludes to and consider a "direct
collapse" black hole as the progenitor of this QSO, rather than building it
out of smaller stellar black holes, we can explore a class of such "evasions".
In essence we need a starless pocket of gas to become dense enough to collapse
_while relatively cold_ into a black hole of perhaps a million solar masses.
Alternatively we could get perhaps ~10 such pockets to collapse into BHs of a
hundred thousand solar masses each, and then rapidly merge. The first approach
tends to create a later Eddington problem: such a BH will generically
interfere with star formation within kiloparsecs, so its subsequent growth is
checked. The second seems to require scenarios like early galaxy-galaxy
mergers, where several smaller galaxies with a direct-collapse BH collide in
such a way that the BHs rapidly merge. This is even harder to model, but has
the advantage of bringing already-formed stars into the neighbourhood of the
SMBH, so it can continue growing.

Lastly, I've found a quick non-technical overview of the problem and the
direct-collapse idea in the context of the CR7 galaxy:
[https://www.ras.org.uk/news-and-press/2887-astronomers-
find-...](https://www.ras.org.uk/news-and-press/2887-astronomers-find-
evidence-for-direct-collapse-black-hole) (and a further quick article with a
pointer to work on the galaxy-galaxy merger idea
[https://www.simonsfoundation.org/2017/03/17/how-
supermassive...](https://www.simonsfoundation.org/2017/03/17/how-supermassive-
black-holes-can-form-without-collapsing-stars/) )

\- --

[1] [http://sci.esa.int/planck/51561-the-history-of-structure-
for...](http://sci.esa.int/planck/51561-the-history-of-structure-formation-in-
the-universe/)

~~~
spyckie2
Thanks. Great stuff, appreciate the slides.

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matte_black
How can a black hole hunger? Doesn’t its consumption mostly depend on how much
matter is around it?

~~~
saagarjha
It's an anthropomorphization.

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methatswho
"Discovery of the most ultra-luminous QSO using Gaia, SkyMapper and WISE"
Publications of the Astronomical Society of Australia (PASA)

free PDF version:
[https://arxiv.org/pdf/1805.04317.pdf](https://arxiv.org/pdf/1805.04317.pdf)

