Extremely large Black Hole discovered 900M years after BB

[Tanelorn]

I thought that this might be a concern for the standard Cosmological model?
An extremely large Black Hole discovered to have existed just 900M years after the Big Bang:

http://www.newscientist.com/article...RSS|NSNS|2012-GLOBAL|online-news#.VO4voq3wthEadded C

 

[phinds]

Not clear why that would have anything to do with the standard model (which is about fundamental particles, not black hole formation) but it does apparently break one of the models of black hole formation which says you just can't get one that big that early according to both the article I read about it (which was different that the one you linked to) and the one you linked to.

 

[martinbn]

I think by the standard model he means the standard cosmological model.

 

[Garth]

Yet another example of well developed objects being found in the early universe An Age Problem (again)?

That thread was prompted by the discovery of a 1.1x10¹⁰M_⊙ BH at z=5.18, and now this BH is ~1.2 × 10¹⁰M_⊙ seen at z=6.30

From the Nature letter http://www.nature.com/nature/journal/v518/n7540/full/nature14241.html#close

So far, roughly 40 quasars with redshifts greater than z = 6 have been discovered. Each quasar contains a black hole with a mass of about one billion solar masses . The existence of such black holes when the Universe was less than one billion years old presents substantial challenges to theories of the formation and growth of black holes and the coevolution of black holes and galaxies. Here we report the discovery of an ultraluminous quasar, SDSS J010013.02+280225.8, at redshift z = 6.30. It has an optical and near-infrared luminosity a few times greater than those of previously known z > 6 quasars.

(emphasis mine)

Is it time yet to question our understanding of the expansion history of the early universe I wonder?

Garth

 

[Chronos]

The existence of supermassive black holes in high z quasars has been known for quite some time and it is not easy to explain them in a bottom up hierarchical model. I think this favors the direct collapse model. In the early universe primordial metallicity was virtually non existent, hence, the usual Jeans mass constraints are not an issue. Just like pop III stars are believed capable of achieving enormous masses, it is not unreasonable to speculate massive primordial gas clouds may have jumped the evolutionary track and collapsed directly into intermediate or supermassive black holes. It appears this would permit sufficient time for the whales known to exist at z=6+ to form. For discussion see http://www.physics.ucsb.edu/news/event/993

 

[Garth]

Other authors are studying the 'Age Problem' and seeking ways of alleviating it: Stars older than the universe and possible mechanism of their creation

An impressive bulk of multiple astronomical observations indicates that there are plenty of objects in the universe with the age which cannot be explained by the conventional theory. A model is considered which successfully describes all these puzzling phenomena.

The 'time breaks down' suggestion can be re-phrased - as I asked in #4, "Is it time yet to question our understanding of the expansion history of the early universe?"

In other words, as we can only observe z and not 't' the latter can not be considered on its own, but only as a factor in the expansion rate of the universe, therefore it is a(t) that is relevant.

If a(t) is modified, say by the existence of another form of DE operating in the early universe, then the age of the universe at a set z can be increased, thus relieving the 'age problem' in the early universe.

One paper that looks at this is Power-law cosmology, SN Ia, and BAO.

Garth

 

[Tanelorn]

Even More here:

http://news.yahoo.com/monster-black-hole-largest-brightest-ever-found-131813505.html

 

[Garth]

Even More here:
http://news.yahoo.com/monster-black-hole-largest-brightest-ever-found-131813505.html

Actually that is the one in your [/PLAIN] [/PLAIN] OP!

Going back to my previous post above, from the paper: Stars older than the universe and possible mechanism of their creation

If no explanation is found in the conventional frameworks there are two possible ways (maybe more) to explain these puzzling phenomena[/PLAIN] [/PLAIN] ,[/PLAIN]
1. A novel mechanism of formation of stellar-type objects in very early universe [1].
2. Modification of the cosmological expansion regime in such a way that the universe becomes older than calculated in the frameworks of the standard model, as is done e.g. in ref. [2]

[/PLAIN] [/PLAIN]
That paper was looking at method 1.) whereas I am more interested in method 2.) which is Dolgovr's paper Power-law cosmology, SN Ia, and BAO.
[/PLAIN] [/PLAIN]
Garth

 

[Tanelorn]

I am starting to favour the argument that supermassive BHs have been created during the BB.

 

[Garth]

The full paper can be found on today's physics arXiv here An ultra-luminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30 {Nature, Vol. 518, 512-515 (2015)}

Garth

 

[Garth]

I am starting to favour the argument that supermassive BHs have been created during the BB.

Yes - but the problem is that if these SMBHs form by the "direct collapse model" (thank you Chronos) in the early stages of the 'BB' then that would be an ultra-bright very quick process at very high z followed by a relatively dark era.

These SMBH's are very bright objects ("ultra-luminous quasar"s) at almost the Eddington limit. Their brightness indicates some form of continuous accretion, and whether you can reconcile that with the age-at-z under the standard \LambdaCDM model is the problem.

Garth

 

[Tanelorn]

This is article is kind of related, I didn't know that the galaxies were this big early on either:
http://phys.org/news/2015-02-galactic-dinosaurs-extinct.html

This article describes the relationship between black hole mass and central bulge mass.
http://phys.org/news/2015-01-relationship-involving-black-holes-galaxies.html#nRlv

That huge BH must have also belonged to a huge galaxy. But this early on after the BB?

 

[Chronos]

In a sufficiently matter rich environment a black hole can feast to godzilla size in a relatively short amount of time. Quasars are believed to be examples of this behavior. AGN galaxies are believed to result when a black hole has consumed most of the matter available to them. That would seem to suggest the most massive SMBH's should be found in such galaxies. I'm not sure if the observational evidence supports this possibility.

 

[Orien Rigney]

Yes - but the problem is that if these SMBHs form by the "direct collapse model" (thank you Chronos) in the early stages of the 'BB' then that would be an ultra-bright very quick process at very high z followed by a relatively dark era.

These SMBH's are very bright objects ("ultra-luminous quasar"s) at almost the Eddington limit. Their brightness indicates some form of continuous accretion, and whether you can reconcile that with the age-at-z under the standard \LambdaCDM model is the problem.

Garth

A simple question. Why, almost immediately as the universe was transitioning from a gaseous state to a solid platform of matter would such a huge black hole be formed?

 

[Garth]

There are three ways of creating early BHs.

Micro-BHs might form in the pre-BBN phase when fluctuations increase local densities creating local Schwarzschild radii entrapping the matter and energy within; these are called 'Primordial Black Holes'.

New cosmological constraints on primordial black holes B. J. Carr, Kazunori Kohri, Yuuiti Sendouda, and Jun’ichi Yokoyama

We update the constraints on the fraction of the Universe going into primordial black holes in the mass range 10⁹–10¹⁷g associated with the effects of their evaporations on big bang nucleosynthesis and the extragalactic photon background. We include for the first time all the effects of quark and gluon emission by black holes on these constraints and account for the latest observational developments. We then discuss the other constraints in this mass range and show that these are weaker than the nucleosynthesis and photon background limits, apart from a small range 10¹³–10¹⁴g, where the damping of cosmic microwave background anisotropies dominates. Finally we review the gravitational and astrophysical effects of nonevaporating primordial black holes, updating constraints over the broader mass range 1–10⁵⁰g.

Primordial Black Holes : Tunnelling vs. No Boundary Proposal Raphael Bousso, R & Stephen Hawking,

In the inflationary era, black holes came into existence together with the universe through the quantum process of pair creation. We calculate the pair creation rate from the no boundary proposal for the wave function of the universe.

These micro-PBHs should be exploding via Hawking radiation about now - although it is generally thought that these have not yet been observed, however these PBMs might be the source of some GRBs and maybe the source of the observed very high energy cosmic rays.

Such PBHs have been suggested as a component of Dark Matter, but because of the 'constraints' discussed in the papers above (and others) they cannot be a major component of DM.

But in answer to your question, "Why, almost immediately as the universe was transitioning from a gaseous state to a solid platform of matter would such a huge black hole be formed?"

Later on after the time of CMB emission and at the beginning of large scale structure formation, DM could form into a dense halo that might attract sufficient baryonic matter to collapse within that total mass's (DM + m) Schwarzschild radius and form a SMBH directly. This so far has been my 'hand waving', but you can work out the details yourself!

Or there might be a population of IMBMs formed as the demise of PopIII stars which might then spiral together into a SMBH (via gravitational wave radiation).

The problem with these last two scenarios is after the initial formation period the mass would be within its Schwarzschild radius and so be dark, but the one observed is 'ultra-luminous' - after all that is why it was found!

There might indeed be dark SMBHs formed by the two processes above that we know nothing about, but the one observed would seem to have had to have been formed by a process of continuous accretion to give it the luminosity.

The problem is that to give such a luminosity the accretion rate is limited by photon pressure - giving the Eddington limit. Our quasar at z=6.30 is right up against this limit as it has a mass of ~1.2x10¹⁰M_⊙ whereas the Eddington Limit at that redshift is 1.3x10¹⁰M_⊙ and so raises the question, "Has there realistically been enough time at z=6.30 for this body to form?"

Garth

 

[Orien Rigney]

Thanks Garth. That information will keep me busy for some time. But another question if I may, is this. What productive good, if any, do BHs perform?

 

[Garth]

Thanks Garth. That information will keep me busy for some time. But another question if I may, is this. What productive good, if any, do BHs perform?

That could be a much bigger question, depending on which speculative theories you are prepared to follow!

As Tanelorn has posted #12 BHs seem to be related in some way to the size and structure of some galaxies. http://phys.org/news/2015-01-relationship-involving-black-holes-galaxies.html#nRlv

They might even be involved in the formation of most galaxies.

In Smolin's Cosmological Natural Selection Theory each BH spawns a new universe through the 'singularity' at its centre. These new universes reflect the physical characteristics (laws, physical constants etc) of their parent universe but with some differences. The process continues with an infinite number of such universes evolving to maximize the number of BH's within them. It so happens that the physical constants necessary for life are also those that maximize the number of BHs within any such universe. So here we are - in this universe together with a lot of BHs!

So a productive good of BH's might be even your own existence, if you believe the theory that is. You can't actually see these other universes of course, and we have no idea what happens inside a BH's 'singularity' (Interstellar not withstanding) so it all depends on what you are prepared to believe in...

BTW Orien, going back to you original question "Why, almost immediately as the universe was transitioning from a gaseous state to a solid platform of matter would such a huge black hole be formed?" - the first half of the question is badly formed. I didn't correct it at the time as my answer was long anyway.

What you are referring to is the process of combination at the time the Cosmic Microwave Background (CMB) was last emitted.

Before then the matter in the universe, mostly hydrogen, was in plasma form. It was ionized into protons and electrons. Light was continuously scattered by this plasma and the universe was therefore opaque.

As the universe expanded its temperature dropped to around 3,000^oK. At this temperature the hydrogen ions and electrons combined into atomic hydrogen. The universe now became transparent and the hydrogen was gaseous.

As we look back the furthest possible distance, we can see this epoch (in the microwave part of the spectrum) as the 'Surface of Last Scattering' about 300,000 years 'after BB' (at z=1100).

The CMB has very slight fluctuations in it, to one part to ~100,000. The fluctuations of over dense matter went onto to form the galactic clusters, and the under dense regions formed the vast voids, that we see in the universe today.

But how this gaseous hydrogen and helium went onto form galactic clusters, galaxies and stars - the Large Scale Structure - is the next part of the story.

DM must have played a major part in getting ordinary matter (baryonic hydrogen and helium) to condense down so quickly into the high-z objects observed in the early universe.

But as your original question went onto ask, and the subject of this thread, - how did such a bright quasar with such a massive BH form so early?Garth

 

[Tanelorn]

I always thought that SMBHs play a very important part in galaxy development, structure and order. Also SMBHs certainly continue to grow over Billions of years, but perhaps they needed to be there first in order for a large galaxy to form instead of structures something like a globular cluster? i.e. What came first the chicken or the egg?

 

[Orien Rigney]

I spent a couple of days musing a period following the Big Bang Theory when stars supposedly started forming. I’m not saying the time line is wrong following the “Dark Ages”, only that the sequence of what came first could possibly be skewed. The link below is NASAs own version of the periods of development. http://www.nasa.gov/images/content/144789main_CMB_Timeline75_lg.jpg
Perhaps when things had cooled to where quarks, gluons and other sub particles began forming into atoms, is it possible this vast universal sea of highly magnetized matter was transformed almost immediately into massive and “condensed galaxies”? Think of one of your first k-12 experiments using iron filings, a bar magnet and a sheet of paper.” Zip”! All of the filings tried to pile up on the one pole when it was extended upward beneath the paper. No mono-poles back then either. Just head to tail, head to tail. Could it be this coalescence created giant orbs that eventually spun themselves into centrifugal dervishes before flying apart to form gaseous galaxies, and then into stars?

 

[Garth]

Perhaps when things had cooled to where quarks, gluons and other sub particles began forming into atoms, is it possible this vast universal sea of highly magnetized matter was transformed almost immediately into massive and “condensed galaxies”? Think of one of your first k-12 experiments using iron filings, a bar magnet and a sheet of paper.” Zip”! All of the filings tried to pile up on the one pole when it was extended upward beneath the paper. No mono-poles back then either. Just head to tail, head to tail. Could it be this coalescence created giant orbs that eventually spun themselves into centrifugal dervishes before flying apart to form gaseous galaxies, and then into stars?

Er no, now you are guessing - if you cannot refer to published articles try not to extend yourself beyond asking questions.

The "quarks, gluons and other sub particles" you referred to began forming nuclei, not atoms (atoms were still in the far future 300,000 years later), at the beginning of Big Bang Nucleosynthesis from ~10^-1 to 10³ seconds, although the process was essentially over after 3 minutes from the 'BB'.

At the Surface of Last Scattering, 300,000 years, later (the origin of the CMB) baryonic matter had to be very smooth and homogeneous to one part in 100,000. Any condensation or accretion of baryonic matter had to happen after this.

Garth

 

[Tanelorn]

Well things are very quiet out there, probably a lot of people are now trying to figure out how to account for this.

 

[Garth]

I always thought that SMBHs play a very important part in galaxy development, structure and order. Also SMBHs certainly continue to grow over Billions of years, but perhaps they needed to be there first in order for a large galaxy to form instead of structures something like a globular cluster? i.e. What came first the chicken or the egg?

That would seem to be a sensible suggestion ('top down' rather than 'bottom up') but how did such large (and in this thread - bright) SMBH's get there so quickly?

Garth

 

[Orien Rigney]

Sorry Garth, I suppose there is more than a bit of ambiguity in my reasoning; and I probably should have offered this link as to my thoughts on the subject. http://origins.stsci.edu/faq/galaxies.html

 

[Tanelorn]

We need JWST asap, assuming it is able to look at these kinds of emissions, frequencies etc.

Another article about this here:
http://www.huffingtonpost.com/dr-st...time_b_6759924.html?ncid=txtlnkusaolp00000592

 

[jal]

900M years after BB
Such a big black hole would have been growing and still be growing.
Is it?
Where is it after 14 B years?

 

[Tanelorn]

It cannot be observed as it is today because of its distance and finite speed of light.

 

[jal]

Does the universe expand at the speed of light and speed of gravity?
If yes, then we would have never seen those black holes.
Those black hole are therefore, within our horizon and still growing.
You should be able to see even bigger black hole that are closer to the present time.

 

[Garth]

Does the universe expand at the speed of light and speed of gravity?
If yes, then we would have never seen those black holes.
Those black hole are therefore, within our horizon and still growing.
You should be able to see even bigger black hole that are closer to the present time.

Those BHs are seen at z > 6, they may be still growing but we would never know that, unless we wait a few billion years to see how they get on.

By that time, however, they may well be beyond our horizon (in a flat universe) if Dark Energy carries on accelerating the universe's expansion.

There indeed may be bigger BH's closer to us that we haven't discovered yet because they are not so bright, or because they are obscured by closer galaxies or dust that have got in the way.

Garth

 

[Tanelorn]

The other problem is that there seems to be only one (or few) of these behemoths..
We should be able to see more examples if they were created early after the BB.

http://en.wikipedia.org/wiki/SDSS_J0100+2802

http://www.huffingtonpost.com/dr-st...time_b_6759924.html?ncid=txtlnkusaolp00000592

 

[Garth]

The other problem is that there seems to be only one (or few) of these behemoths..
We should be able to see more examples if they were created early after the BB.

http://en.wikipedia.org/wiki/SDSS_J0100+2802

http://www.huffingtonpost.com/dr-st...time_b_6759924.html?ncid=txtlnkusaolp00000592

Whereas SDSS J0100+2802 (the subject of this thread) is one of the most luminous the paper An ultra-luminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30 states

So far, roughly 40 quasars with redshifts greater than z= 6 have been discovered. Each quasar contains a black hole with a mass of one billion solar masses (10⁹M_⊙)

(emphasis mine)

So a bit more than "one, or a few".

Garth

 

[Tanelorn]

Whereas SDSS J0100+2802 (the subject of this thread) is one of the most luminous the paper An ultra-luminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30 states (emphasis mine)

So a bit more than "one, or a few".

Garth

What I meant was, this one was quite a bit larger than the rest. i.e, 12 Billion solar masses. (see plot here. not log scale)
http://www.washingtonpost.com/news/...cient-black-hole-the-size-of-12-billion-suns/

Interesting, this quasar has a redshift over 7.1 making it even more difficult to explain, observed at 770 million years after thee BB with 2 billion solar masses.
http://en.wikipedia.org/wiki/ULAS_J1120+0641This group of quasars challenges Einstein's homogeneous requirements:
http://news.discovery.com/space/galaxies/scientists-find-universes-largest-structure-130111.htmA very interesting alignment of spin axes (see video)
http://en.wikipedia.org/wiki/Quasar

Largest ever quasar:
http://www.popsci.com/science/artic...gest-quasar-ever-near-supermassive-black-hole

 

[Garth]

Thank you Tanelorn,

That ULASJ1120+0641 has a luminosity of 6.3×10¹³L_⊙ and hosts a black hole with a mass of 2×10⁹M_⊙ at z=7.085, is beyond the Eddington Limit.

The only way to get this big, and still be bright is with a combination of formation routes

You need a SMBH very early and the only way to get that is with either a direct collapse of baryonic matter into a DM potential well, or a merger of many IMBHs at say z~10 (cosmic age 480Myrs), together with a later (z~8ish cosmic age 650Myrs) accretion of stars, matter etc. forming a bright accretion disc that gives the observed lumninosity.
The problem with this as I see it is that the SMBH mass is so large that its Event Horizon tidal forces are so small that they would swallow up the said stars without forming an accretion disc.

So, unless others can enlighten me, it does seem that we do have an age problem here in the early universe - the universe is younger at this red shift than this object within it.

Garth

 

[wabbit]

Interesting - so how big is the discrepancy? Say, would it be enough to revise the age of the universe by say 200My for the formation process to fall within reasonably expected behaviour, or would it need to be more substantial?

 

[Garth]

There may not be an age-problem after all (although it is close!) Several papers talk about Super Eddington accretion.

SUPER-CRITICAL GROWTH OF MASSIVE BLACK HOLES FROM STELLAR-MASS SEEDS

We consider super-critical accretion with angular momentum onto stellar-mass black holes as a possible mechanism for growing billion-solar-mass black holes from light seeds at early times. We use the radiatively inefficient "slim disk" solution—advective, optically thick flows that generalize the standard geometrically thin disk model—to show how mildly super-Eddington intermittent accretion may significantly ease the problem of assembling the first massive black holes when the universe was less than 0.8 Gyr old. Because of the low radiative efficiencies of slim disks around non-rotating as well as rapidly rotating black holes, the mass e-folding timescale in this regime is nearly independent of the spin parameter. The conditions that may lead to super-critical growth in the early universe are briefly discussed.

X-rays from the redshift 7.1 quasar ULAS J1120+0641.

Super-Eddington accretion would help to reduce the discrepancy between the age of the quasar implied by the small size of the ionized near-zone in which it sits (<10⁷ yr) and the characteristic e-folding time (2.5 × 10⁷ yr if L/LEdd = 2). Such super-Eddington accretion would also alleviate the challenging constraints on the seed black hole mass provided that the quasar has been rapidly accreting throughout its history. The remnant of an individual Population III star is a plausible progenitor if an average L/LEdd > 1.46 has been maintained over the quasar's lifetime.

If a insurmountable age-problem should arise then as I have indicated in my post #6 above a solution might be a modification of a(t) by the presence of another form of DE in the early universe. As we have already added DE to the later universe to make the distant SNe 1a fit, this shouldn't require too great a stretch of the imagination!

For example if we had linear expansion, a(t) = t, then the age at z=7 would be ~2Gyrs and not 770Myrs, more than double the time to 'make things'.

Garth

 

[wabbit]

Thanks ! Indeed I understand if there is an age problem presumably it would be resolved by some changes/tweaks in the model, maybe in the inflation etc... a few 100Mys doesn't sound like that much (I imagine >>1bn years might be another challenge)

 

[wolram]

to show how mildly super-Eddington intermittent accretion may significantly ease the

a lot of things may be.

 

[zoki85]

Let somebody calculate the Schwarzschild radius of it (I'm too lazy)
Here is the formula:

 

[Tanelorn]

List of most distant red shifted events:
http://en.wikipedia.org/wiki/List_of_the_most_distant_astronomical_objects

 

[Garth]

Let somebody calculate the Schwarzschild radius of it (I'm too lazy)
Here is the formula:

The Schwarzschild radius is linearly proportional to M.

The Solar Schwarzschild radius is 2.95 km, so call it roughly 3 km - a 10¹⁰ M_⊙ BH has a Schwarzschild radius of 3x10¹⁰ km.

Garth

 

[wabbit]

a 10¹⁰ M_⊙ BH has a Schwarzschild radius of 3x10¹⁰ km.

So, 200 AU. Respectable.

 

[Tanelorn]

Isn't that bigger than the super massive black hole at the center of the milky way over 12B years later?

These are Radii:

http://en.wikipedia.org/w/index.php?title=Saggitarius_A*_(SMBH)&action=edit&redlink=1 1.27×10^10 meters
http://en.wikipedia.org/w/index.php?title=Andromeda_(SMBH)&action=edit&redlink=1 4.68×10^11 meters
http://en.wikipedia.org/w/index.php?title=NGC_4889_(SMBH)&action=edit&redlink=1 6.2×10^13 meters !http://en.wikipedia.org/wiki/Schwarzschild_radius

Aside: The observable universe's mass has a Schwarzschild radius of approximately 13.7 billion light years!

 

[mfb]

Does the universe expand at the speed of light and speed of gravity?
If yes, then we would have never seen those black holes.
Those black hole are therefore, within our horizon and still growing.
You should be able to see even bigger black hole that are closer to the present time.

Speed is a bad measurement of expansion, because this speed depends on the distance of the object, and there are multiple ways to define "speed" for large distances.
The light emitted there 900 million years needed about 13 billion years to reach us. The light emitted there 1 year later will need 7.3 years more. So we can follow its evolution, but to see how it evolves over millions years we would have to watch for many millions of years. For very long timescales, we cannot neglect the accelerated expansion of the universe any more - this factor of 7.3 will increase more and more, to a point where the quasar redshifts into oblivion. Assuming nothing dramatic changes the future evolution of the universe, we will never see how the black hole looks like today.

 

[Garth]

Isn't that bigger than the super massive black hole at the center of the milky way over 12B years later?

Yes - the Milky Way's BH Sagittarius A has a mass of 4.5x10⁶M_⊙ I was working out the Schwarzschild radius of a 10¹⁰M_⊙ BH.

The Milky Way's SMBH is quite small as far as SMBH's are concerned, and it is also rather quiet - which is probably a good thing for us fragile biological beings here on Earth!

Aside: The observable universe's mass has a Schwarzschild radius of approximately 13.7 billion light years!

That's because the universe is flat - or nearly so - and its average density is the critical density.

Garth

 

[Jorrie]

http://en.wikipedia.org/wiki/Schwarzschild_radius
Aside: The observable universe's mass has a Schwarzschild radius of approximately 13.7 billion light years!

Approximately only if you include dark energy in the "observable universe's mass", in which case it is about 14.4 billion light years. This is rather the Hubble radius, because I do not think a Schwarzschild radius makes much sense on cosmic scales.

 

[Garth]

Yes, let's do the Maths:

Now the cosmological critical density is given by:

And the Schwarzschild radius is given by:

The density of mass in a sphere (Euclidean - flat - geometry) is given by:
\rho = \frac{3m}{4\pi r^3}
So the Schwarzschild density - the average density of a mass within the Schwarzschild radius is given by substituting for m from the formula for r_s :
\rho_s = \frac{3c^2}{8\pi Gr^2}
And as the age of our universe is equal to or almost equal to Hubble time (due to a fortuitous coincidence in the effect of DE - see Age of universe) we can set H = c/r so:
\rho_s = \frac{3H^2}{8\pi G}
The critical density!

But as Jorrie said "I do not think a Schwarzschild radius makes much sense on cosmic scales"

In fact we can go further, the Schwarzschild solution is a solution of the GR One Body Problem embedded in a Minkowski space-time - it is totally inappropriate to apply it to the GR cosmological solution. The similarity of the numbers just gives a feel of how the GR Field Equation works in the two solutions, one the 'static spherically symmetric solution' and the other the 'maximally symmetric space solution' - nothing more.

Garth

 

[Tanelorn]

This wiki page describes all known alternative Cosmologies:
http://en.wikipedia.org/wiki/Non-standard_cosmology

 

[Garth]

This wiki page describes all known alternative Cosmologies:
http://en.wikipedia.org/wiki/Non-standard_cosmology

Not quite all: Gravity

Alternative theories

Recent alternative theories

Brans–Dicke theory of gravity (1961) [31]
Induced gravity (1967), a proposal by Andrei Sakharov according to which general relativity might arise from quantum field theories of matter
ƒ(R) gravity (1970)
Horndeski theory (1974) [32]
Supergravity (1976)
String theory
In the modified Newtonian dynamics (MOND) (1981), Mordehai Milgrom proposes a modification of Newton's Second Law of motion for small accelerations [33]
The self-creation cosmology theory of gravity (1982) by G.A. Barber in which the Brans-Dicke theory is modified to allow mass creation
Loop quantum gravity (1988) by Carlo Rovelli, Lee Smolin, and Abhay Ashtekar
Nonsymmetric gravitational theory (NGT) (1994) by John Moffat
Tensor–vector–scalar gravity (TeVeS) (2004), a relativistic modification of MOND by Jacob Bekenstein
Gravity as an entropic force, gravity arising as an emergent phenomenon from the thermodynamic concept of entropy.
In the superfluid vacuum theory the gravity and curved space-time arise as a collective excitation mode of non-relativistic background superfluid.
Chameleon theory (2004) by Justin Khoury and Amanda Weltman.
Pressuron theory (2013) by Olivier Minazzoli and Aurélien Hees.

(emphasis mine -if I may?)

Garth

 

[Tanelorn]

The most massive structure at a distance of 7.5B Light years:

http://phys.org/news/2011-04-massive-distant.html#nRlv
One of the most interesting results of this discovery is that, if current models of how the universe evolved are accurate, clusters of this size are very rare in the young universe. In fact, this cluster could even be unique.

http://phys.org/news/2010-10-ghosts-future-giant-universe.html#nRlv
Even at that young age, the cluster was almost as massive as the nearby Coma cluster. Since then, it should have grown about four times larger. If we could see it as it appears today, it would be one of the most massive galaxy clusters in the universe.