[timey (OP)]

LIGO...  What are the probabilities?

http://www.nature.com/news/ligo-black-hole-echoes-hint-at-general-relativity-breakdown-1.21135?WT.ec_id=NEWS-20161215&spMailingID=52998738&spUserID=MjgzNDMxNjU2ODIS1&spJobID=1063046368&spReportId=MTA2MzA0NjM2OAS2

In a universe that is not only expanding, but is currently accelerating in this expansion, it strikes me as peculiar that LIGO is detecting these black hole mergers.

It is understood that there is thought to be a black hole in the centre of most galaxies, and it is also understood how there are thought to be rouge black holes that are not associated with galaxies...

Clearly LIGO are detecting the black hole that is not associated with a galaxy.

What I find peculiar under the premise of this accelerated expansion, is the fact that these huge masses that I would have thought, under the premise of accelerated expansion to be far flung apart from each other, are in fact observed to be merging as mass clumping together...

Any thoughts?

[timey (OP)]

These black hole pairs should arise from binary star systems within galaxies. Both stars having enough mass to collapse into a black hole when all their fuel is exhausted. Think of it like a solar system with two suns. The dynamics of the system will be inherently unstable. Which is what ultimately causes the black hole merger.

...this is a very reasonable explanation for the existence of black hole mergers and indeed is the only truly viable explanation for black hole mergers occurring in an expanding universe.

Have you any thoughts on the fact that in such short amount of time LIGO have detected 3 separate mergers?

[jeffreyH]

That there are a lot of binary black hole systems out there.

[Janus]

LIGO...  What are the probabilities?

http://www.nature.com/news/ligo-black-hole-echoes-hint-at-general-relativity-breakdown-1.21135?WT.ec_id=NEWS-20161215&spMailingID=52998738&spUserID=MjgzNDMxNjU2ODIS1&spJobID=1063046368&spReportId=MTA2MzA0NjM2OAS2

In a universe that is not only expanding, but is currently accelerating in this expansion, it strikes me as peculiar that LIGO is detecting these black hole mergers.

It is understood that there is thought to be a black hole in the centre of most galaxies, and it is also understood how there are thought to be rouge black holes that are not associated with galaxies...

Clearly LIGO are detecting the black hole that is not associated with a galaxy.

What I find peculiar under the premise of this accelerated expansion, is the fact that these huge masses that I would have thought, under the premise of accelerated expansion to be far flung apart from each other, are in fact observed to be merging as mass clumping together...

Any thoughts?

The expansion of the universe only applies at at large scales (larger than galaxy clusters), structures smaller than this are bound by gravity. 

There are also black holes that are members of galaxies but not the central black hole.  There is no evidence that the black holes detected in the merger were not such members of a galaxy. Since their masses (30 and 35 solar masses) are in the range expected for stellar black holes (one formed by the collapse of massive stars) is is reasonable to assume that they were formed from a binary star system, and thus a gravitationally bound pair to begin with.  These then spent billions of years shedding orbital energy as gravitational radiation, until 1.3 billion years ago they finally merged creating the spike in gravitational waves we detected.  There is no telling how many of these massive black hole binaries are in the universe.

[timey (OP)]

That there are a lot of binary black hole systems out there.

http://www.space.com/1995-astronomers-wrong-stars-single.html

Maybe there 'were' more binaries, but according to above link only 25% of red dwarfs are binary.  Red dwarfs make up 85% of stars in Milky Way, and the other brighter stars are thought to be a little over half binary.

It's states in the link that although there are theories as to why both singles and binaries may form, there is no theory describing why one type may form more than the other.

On the basis that perhaps both types of system started out equally apportioned, and that binaries will be less stable than singles, could we expect to detect as many missing binary systems that are now at the black hole merger stage?

Or contrarily to your post, did the universe produce, for reasons unfathomable, more singles than binaries?

[timey (OP)]

LIGO...  What are the probabilities?

http://www.nature.com/news/ligo-black-hole-echoes-hint-at-general-relativity-breakdown-1.21135?WT.ec_id=NEWS-20161215&spMailingID=52998738&spUserID=MjgzNDMxNjU2ODIS1&spJobID=1063046368&spReportId=MTA2MzA0NjM2OAS2

In a universe that is not only expanding, but is currently accelerating in this expansion, it strikes me as peculiar that LIGO is detecting these black hole mergers.

It is understood that there is thought to be a black hole in the centre of most galaxies, and it is also understood how there are thought to be rouge black holes that are not associated with galaxies...

Clearly LIGO are detecting the black hole that is not associated with a galaxy.

What I find peculiar under the premise of this accelerated expansion, is the fact that these huge masses that I would have thought, under the premise of accelerated expansion to be far flung apart from each other, are in fact observed to be merging as mass clumping together...

Any thoughts?

The expansion of the universe only applies at at large scales (larger than galaxy clusters), structures smaller than this are bound by gravity. 

There are also black holes that are members of galaxies but not the central black hole.  There is no evidence that the black holes detected in the merger were not such members of a galaxy. Since their masses (30 and 35 solar masses) are in the range expected for stellar black holes (one formed by the collapse of massive stars) is is reasonable to assume that they were formed from a binary star system, and thus a gravitationally bound pair to begin with.  These then spent billions of years shedding orbital energy as gravitational radiation, until 1.3 billion years ago they finally merged creating the spike in gravitational waves we detected.  There is no telling how many of these massive black hole binaries are in the universe.

https://stardate.org/astro-guide/galaxy-formation

Whichever theory one employs as to the formation of galaxies, the above link is suggestive that mass is still clumping on a massive scale.  Yet it is also thought that 'most' galaxies are moving further apart from each other, and that the component stars of galaxies are also slowly drifting further apart.

Observation of outer galaxy orbital speeds have led to the inclusion of Dark Matter to maintain current theory, and observation of accelerated expansion via red shift interpretation has also led to the inclusion of Dark Energy, again to maintain current theory...

...but why would Dark Energy be more energetic between galaxies?
...and given that current physics is saying that Dark Energy is more energetic between galaxies than it is within them, can someone give me some indication as to exactly which direction in space Dark Energy is choosing to push everything away from?
...and explain how this Dark Energy force is supposed to occur as a directional force within the 3 dimensional space that surrounds each galaxy?

Anyway, leaving Dark Energy for the mo... merger black holes under the remit of current theory can only result via the development of unstable non-singular star systems.
The link I posted in my last post stated that there is a theory to support the formation of single star systems, and another theory to support the formation of non-singular star systems, but there is no theory to suggest why one type may form more prolifically than the other, and that previously held theories holding binary systems as more prolific than singles are actually wrong.

I suggested that if both types had started out in equal number, the fact of the instability of binary systems might insure that evolution over time resulted in there being a prolific number of black hole mergers, and a lesser number of binary star systems than singles, as is observed.

However, wouldn't the notion of the discovery of such a prolific number of black hole mergers within a galaxy go on to change the gravitational outlook of how we interpret a galaxy interacting within itself, and if so, then how?

The Milky Way has been merged with several other galaxies over the eons, so binary systems may have resulted from this cause, rather than from being birthed at the same time from a gaseous cloud fragmented by turbulence...
Given that binary systems would evolve as a result of the earlier formation of singular systems, would this result in a less prolific number of black hole mergers overall in the universe, than if binary star systems were birthed from gaseous clouds as singulars are?  This being because the binaries will have had less time in which to evolve into the, until recently undetectable, black hole mergers.  If so, then the number of black hole mergers will not be as prolific.

...and again I ask, how many detections of unknown massive black hole mergers, within 1 galaxy, would it take to significantly change the gravitational outlook as to how that galaxy interacts within itself?

...But it is the fact of galaxies merging at-all that returns me to the initial question as to peculiarity...
Why are galaxies that are forming while being accelerated 'away' directionally by Dark Energy (from a point) actually merging with each other at-all, when distance is proportional to velocity?

[evan_au]

accelerated 'away' directionally by Dark Energy (from a point)

The expansion of the universe has distant galaxies all moving away from each other.
There is no single point they are moving away from - every point is moving away from every other point (on large scales).

Why are galaxies that are forming while being accelerated 'away' directionally by Dark Energy (from a point) actually merging with each other at-all, when distance is proportional to velocity?

Our Milky Galaxy and the "nearby" Andromeda galaxy are all part of our local cluster of galaxies.
They are not distant galaxies, in the context of Dark Energy.

As Janus said, this local cluster is gravitationally bound, with random motion within the cluster.
- At this point in time, Dark Energy has no visible impact on this scale - it applies only on scales much larger than the local cluster
- However, Dark Matter is important, in holding the local cluster together.

The Andromeda galaxy is moving towards our galaxy as part of these random local motions, and these neighbouring galaxies are expected to collide in about 5 billion years, around the same time the Sun turns into a red giant.

Maybe there 'were' more binaries, but according to above link only 25% of red dwarfs are binary.  Red dwarfs make up 85% of stars in Milky Way, and the other brighter stars are thought to be a little over half binary.

Despite their large numbers, Red Dwarfs do not go on to form black holes - they are far too small, being smaller than the Sun.
You need a star that starts with a mass of 10 solar masses or more to have enough mass left at the end of its life to form a black hole.

there is a theory to support the formation of single star systems, and another theory to support the formation of non-singular star systems

In fact, it is thought that stars are formed in groups of dozens to thousands in a stellar nursery consisting of cold, dark gas and dust.

Any system of 3 or more objects is unstable in the long term, with third parties being expelled, leaving two objects which are closely gravitationally bound. And because they are gravitationally bound, they are immune from the effects of Dark Energy.

So this leaves a mix of solo stars and binary stars. It is expected that planets will be more common around solo stars, since in a binary star system, the planets become a "third party", and are more likely to be ejected.

When two massive objects are in a close orbit, gravitational waves slowly radiate away their angular momentum, so they approach each other more closely. Dark Energy has no impact on these scales.

Clearly LIGO are detecting the black hole that is not associated with a galaxy.

I think that this might misrepresent the situation.
In intergalactic space, stars are quite rare; the odds are against two black holes approaching each other and coming into a close orbit (remember, this often requires the presence of a third party, which is even less likely).

However, in a galactic disk, stars (and black holes) are fairly dense - and even denser in the galactic bulge or globular clusters. Black holes are fairly likely to encounter one another in this environment - and to find the third parties that allow them to come into a close orbit. So merging black holes are more likely to occur in a galaxy.

Where the confusion may have occurred is with galaxy-core black holes, which are also associated with galaxies. LIGO does not have enough sensitivity at the very low frequencies that would be generated with mergers of galaxy-core black holes. It can only detect frequencies around 50Hz to 1kHz - the frequencies you expect from the merger of stellar-mass black holes and neutron stars.

In fact, the first detection was of black holes with original mass around 30 solar masses, which were a bit larger than your "typical" stellar-mass black hole (more like 1.5 to 10 solar masses). This frequency was at the low-frequency end of the LIGO frequency response.

[timey (OP)]

I have heard the pumpkin field analogy applied to the current physics inflation period, where one imagines that the field the pumpkin are planted in grows at the same rate as the pumpkins do...
If Dark Energy is pushing outwards in every direction from each and every galaxy, then all this energy will do overall is push the content of galaxies closer together...surely?

*

I am aware of the location of the Milky Way in the local galaxy cluster, Andromeda's blue shifted trajectory, the lacking of the necessity for Dark Energy in such a gravitationally bound cluster, and the necessity for Dark Matter to maintain such gravitational binding.

But why have the galaxies clustered, and where were they before clustering?

*

Ok, so red dwarfs are not big enough to become black holes and only 25% of them (as per the Milky Way) are binary.
It is interesting that you say that more complex binary systems eject third parties, because this cuts the possibility of development of black hole mergers, within a galaxy of the same proportion of red dwarfs to brighter bigger stars as the Milky Way has, down considerably.
Red dwarfs make up 85% of the Milky Way leaving 15% bigger stars of which a little over half are thought to be binary...with most of the bigger of these stars being binary.  But how many of these bigger star binary systems hold stars that are big enough to develop into black holes? ...and how many of these bigger star binary systems that might of previously had stars big enough to develop into black holes have developed into black hole mergers already?

*

Here is the link I posted earlier:

http://www.space.com/1995-astronomers-wrong-stars-single.html

Quote:
""Recent observations show that half a dozen new stars are produced each year in the Milky Way, but many of the details surrounding their births remain unclear. According to the classical theory, stars form when large clouds of dust and gas in space collapse under the force of gravity. If these dense cores of matter reach a critical limit, internal nuclear fires ignite and new stars are born.
However, this theory doesn't explain why most large stars tend to have companions.
"There are theories that can form binary stars and theories that can form single stars, but there none that explain why you form more singles than binaries," Lada told SPACE.com.

Astronomers have some ideas though. Observations have shown that the large clouds that serve as stellar nurseries for massive stars are more turbulent than small clouds where red dwarfs are thought to typically come from. It could be that this turbulence causes massive stars to form in groups of two or more.

"If the [large clouds] have some initial turbulent motions, then as they collapse, they will tend to split up," Lada explained.""

Unquote:

I am discussing the matter in context of how many black hole mergers we can expect to be detected on the basis of differing theories on how stars are formed.  If the turbulent gas cloud theory is not viable, then the alternative is that stars become binary via galaxy mergers rather than being born as binary via turbulent gas cloud.  My point being that if binary systems are the result of mergers rather than gas cloud turbulence, then the probability is that black hole mergers will not be as prolific as they would be if binaries were created at the Stella nursery stage along with singular star systems.

*

What I meant was that LIGO are not detecting a black hole merger associated with the super massive black hole that is supposed to be at the centre of any galaxy.  What they are detecting are mergers of black holes that are within a galaxy.  No I did not imagine black holes roaming between galaxies. .  No confusion there thank you.

If binary systems are created at the gaseous cloud stage rather than, as suggested above, just via merging singular star systems, does this mean that we can expect LIGO to detect a more prolific amount of black hole mergers than they would if binary systems were only created by the merging of already developed singular star systems?

[evan_au]

But why have the galaxies clustered, and where were they before clustering?

Analysis of the Cosmic Microwave Background Radiation shows that the early universe had some small random density variations.
Galaxy clusters would have been more likely to form where matter was denser.

Over time, the areas that were slightly more dense would have attracted matter  out of the less-dense regions. This is a positive feedback process.

Modern studies suggest that the matter in the universe today is distributed like the liquid in soap bubbles, with matter in thin walls separating large voids of apparently little matter. In this analogy, the galaxy clusters are distributed along the joins between the soap bubbles.

See: https://en.wikipedia.org/wiki/Observable_universe#Large-scale_structure

[timey (OP)]

Thanks Evan - that link was an interesting read, especially the comments on differing estimates, or interpretations regarding the size and distance of the unobservable parts of the universe.

I have previously seen the given picture of the observable universe since the redshift mapping was completed, and understand that deviations from an initial uniformity will have gone on to develop into areas that are more clumped with mass than others.
(Of course I can't help but wonder what such mapping would look like under the remit of my models interpretation of redshift observation).

But going back to the discussion of how many black hole mergers we can expect LIGO to go on to detect, in relation to how it is that binary star systems may or may not be caused... Have you any thoughts?