Black holes and dark matter linked?

[SimpleRick]

Am completely new to this, and could only classify myself as a layman in physics terms, but an interesting thought occurred to me recently:

While watching " Cosmos" recently, I started thinking about what was said about the expansion of the universe. If we take as a given that at the centre of each galaxy is a supermassive black hole which is consuming matter and growing as a result of this, why would our galaxy still be expanding? So what if all the matter that is being absorbed by the black hole is being turned from matter into 'dark matter'? The black hole might be an instrument which takes in matter spewing out dark matter, which would be amassing and pressing down on our galaxy. This would explain why our galaxy is expanding faster, the pressure from all the dark matter building up is squeezing the galaxy and therefore the outskirts would be moving faster. This could also help explain our alleged perception that time is moving faster than it used to, time is moving faster because matter is moving faster through the universe. And it could help explain the amount of dark matter in the galaxy.

All this is but a theory, I have no mathematical skills whatsoever, so I can't do the maths, but anyone who could put this into an equation (or similar) is welcome to use this as a basis...

 

Would be interested to hear whether anyone thinks this theory might be plausible, or whether it is complete poppycock...

 

Norman Jones

[Silvestru]

30 minutes ago, SimpleRick said:

If we take as a given that at the centre of each galaxy is a supermassive black hole which is consuming matter and growing as a result of this, why would our galaxy still be expanding?

Hello and welcome to the forum.

It's not just our Galaxy that is expanding, it's the whole universe and it is expanding evenly in all directions.

Here is a graph of kind of how it works but do not imagine that the Universe has any boundaries like the spheres below (it might, we just don't know yet).

 

30 minutes ago, SimpleRick said:

So what if all the matter that is being absorbed by the black hole is being turned from matter into 'dark matter'?

Matter being absorbed is not being turned into dark matter.  Dark matter is something completely different. AFAIK only Hawking radiation leaks from a black hole and nothing else, not even light.

https://en.wikipedia.org/wiki/Dark_matter

https://en.wikipedia.org/wiki/Hawking_radiation

 

Just as an addition the term Dark matter, Dark energy was misleadingly coined to show that we cannot detect this matter or energy, we have no or little observational evidence for them.

The term dark does not describe their colour or composition. We just suspect they might exist  to explain some processes in our Universe, like the rapid expansion that you mentioned (dark energy) or the gravitational "anomalies". (dark matter accounts for about 80% of mass energy in the observable Universe)

Edited April 18, 2018 by Silvestru

[Strange]

28 minutes ago, SimpleRick said:

If we take as a given that at the centre of each galaxy is a supermassive black hole which is consuming matter and growing as a result of this, why would our galaxy still be expanding?

Most black holes are not consuming any significant amount of matter. We know this, because when they do, the matter falling in gets incredibly hot and generates a lot of radiation and even seeds jets of matter out at nearly the speed of light. We see this as the relatively small number of quasars and "active" galaxies.

Also, galaxies are not, in general, expanding. They are pretty stable (apart from occasional collisions).

Expansion only happens at very large scales. It is the space between galaxies that is increasing. Actually, it is the space between clusters of galaxies that is increasing. (Which is why galaxies in clusters can collide with one another!)

31 minutes ago, SimpleRick said:

So what if all the matter that is being absorbed by the black hole is being turned from matter into 'dark matter'? The black hole might be an instrument which takes in matter spewing out dark matter, which would be amassing and pressing down on our galaxy.

There is no evidence that anything can come out of a black hole or that they can convert matter to dark matter. And no theoretical reason to think it might happen.

Welcome to the forum!

[Silvestru]

36 minutes ago, SimpleRick said:

If we take as a given that at the centre of each galaxy is a supermassive black hole

Just as a fun-fact not all galaxies have  super-massive black hole in the centre.

Quote

On September 10, 2012, using Hubble Space Telescope's Wide Field Camera 3, scientists found out that there was no supermassive black hole present in the center.^[2] This may be the likely cause of its diffuse and large core, but it contradicts modern galactic evolutionary theories. A huge cD galaxy like A2261-BCG would be expected to have a supermassive black hole concentrated at its center.

https://en.wikipedia.org/wiki/A2261-BCG

[Strange]

Also, worth noting that these black holes might be "supermassive" but they make up a minute proportion of the mass of the galaxy and so only have a direct effect on the few stars directly orbiting them.

From: http://www.skyandtelescope.com/astronomy-news/milky-ways-central-monster-measured/

[StringJunky]

2 hours ago, Strange said:

Also, worth noting that these black holes might be "supermassive" but they make up a minute proportion of the mass of the galaxy and so only have a direct effect on the few stars directly orbiting them.

From: http://www.skyandtelescope.com/astronomy-news/milky-ways-central-monster-measured/

But aren't all the rotating bodies gravitationally linked by a daisy chain effect, so its presence is crucial?

[Strange]

1 hour ago, StringJunky said:

But aren't all the rotating bodies gravitationally linked by a daisy chain effect, so its presence is crucial?

Not sure what you are thinking of. The orbit of a star (the Sun, for example) around the galaxy is determined (largely) by the total mass inside its orbit. It doesn't matter much where that mass is or what form it takes (assuming it is roughly evenly distributed).

So the black hole contributes some tiny fraction of that mass. But it would be exactly the same as if that same mass were in multiple stars spread out through the galaxy.

[StringJunky]

10 minutes ago, Strange said:

Not sure what you are thinking of. The orbit of a star (the Sun, for example) around the galaxy is determined (largely) by the total mass inside its orbit. It doesn't matter much where that mass is or what form it takes (assuming it is roughly evenly distributed).

So the black hole contributes some tiny fraction of that mass. But it would be exactly the same as if that same mass were in multiple stars spread out through the galaxy.

I'm thinking that the combined gravitational effect of the inner stars progressively attract the adjacent outer ones. Imagine the SMBH in the centre, and there was just one star at a distance of the extreme edge of the Milky way; would that SMBH hold that star in orbit? Or to put it another way: will the SMBH hold a star 50KLYRS away in an orbit?

Edited April 18, 2018 by StringJunky

[Janus]

5 hours ago, SimpleRick said:

Am completely new to this, and could only classify myself as a layman in physics terms, but an interesting thought occurred to me recently:

While watching " Cosmos" recently, I started thinking about what was said about the expansion of the universe. If we take as a given that at the centre of each galaxy is a supermassive black hole which is consuming matter and growing as a result of this, why would our galaxy still be expanding? So what if all the matter that is being absorbed by the black hole is being turned from matter into 'dark matter'? The black hole might be an instrument which takes in matter spewing out dark matter, which would be amassing and pressing down on our galaxy. This would explain why our galaxy is expanding faster, the pressure from all the dark matter building up is squeezing the galaxy and therefore the outskirts would be moving faster. This could also help explain our alleged perception that time is moving faster than it used to, time is moving faster because matter is moving faster through the universe. And it could help explain the amount of dark matter in the galaxy.

All this is but a theory, I have no mathematical skills whatsoever, so I can't do the maths, but anyone who could put this into an equation (or similar) is welcome to use this as a basis...

 

Would be interested to hear whether anyone thinks this theory might be plausible, or whether it is complete poppycock...

 

Norman Jones

A couple of points: The Supermassive BH at the center of the galaxy is is pretty much through absorbing matter.  It cleared out the vast majority of the close-by stuff long ago.  The rest of the material went into orbit around that Black hole. After you get any distance from a black hole, it gravity behaves just like that of any other object.  If we look deep into the universe ( and thus into the past), we see very bright objects originally named Quasars, they turned out to be young galaxies where the Black holes at their centers were still gobbling up matter.  The high speed collisions between the stuff being pulled into the BH caused the region around to to emit a lot of high energy radiation.  If our BH was still actively absorbing matter like this, our galaxy would be presently irradiated to point that life would be impossible.  Even if it was absorbing matter, it could not spew dark matter.  The difference between DM and "normal matter" is that DM does not interact with light or electromagnetically in any way.  It only strong interaction it participates in is gravity.  Since it is gravity that prevents escape from the event horizon of a black hole, DM would be no more capable of escape than normal matter.

Our galaxy is not expanding.  It is be held together by the mutual gravitation attraction of it components. Dark matter comes into play in that the visible matter isn't enough to hold the galaxy together against the rate at which it spins.     Dark matter come into play by providing the additional gravity needed to hold the galaxy together.  To do this job in a way that is consistent with how stars are measured orbiting the galaxy, DM has to have a certain type of distribution, which is pretty evenly spread out through the galaxy. 

If DM were being produced at the center of the galaxy, then it would be much denser there and thin out as you moved outward.  This would produce a much different rotation profile for the galaxy than what we observe.

Another point that should be made is that sometimes people make too much out of the "supermassive" part of supermassive black hole.  Yes, they are massive in terms of a typical star (The SMBH at the center of our galaxy is some 4 million times more massive than our Sun),  but it quite small compared to the mass of the galaxy itself( 5.8 x 10¹¹  times the mass of the sun or 145,000 times more massive than the SMBH at its center). So when it comes to the overall gravitational effect of the galaxy, it is quite a small player.

[Strange]

1 hour ago, StringJunky said:

I'm thinking that the combined gravitational effect of the inner stars progressively attract the adjacent outer ones

That is true. But it is really just the total mass of the matter within a given orbital distance that matters. So, while it is true that the stars further out are held in place by the stars further in, the black hole doesn't really have a special role in this. Any distribution of the same mass would have the same effect.

[StringJunky]

2 minutes ago, Strange said:

That is true. But it is really just the total mass of the matter within a given orbital distance that matters. So, while it is true that the stars further out are held in place by the stars further in, the black hole doesn't really have a special role in this. Any distribution of the same mass would have the same effect.

OK. A bit like gas clouds?

[Strange]

32 minutes ago, StringJunky said:

OK. A bit like gas clouds?

Yes, pretty much. At a rage enough scale, you can treat the galaxy as a fairly homogeneous cloud of "stuff". Although, there are different "layers" - the central bulge is spherical and has a different density distribution that the disk, etc.

[beecee]

2 hours ago, Strange said:

That is true. But it is really just the total mass of the matter within a given orbital distance that matters. So, while it is true that the stars further out are held in place by the stars further in, the black hole doesn't really have a special role in this. Any distribution of the same mass would have the same effect.

While I agree and am fully aware of that situation, could it not be said that the SMBH at the center of most galaxies, does act as a sort of anchor for the rest of the galaxy?

I do remember a few years ago, coming across an article detailing the finding of a galaxy much larger [more disperse] then the MW galaxy, but without any SMBH at the core. The disperse nature of the BH [from memory] was attributed to it lacking any SMBH,

[Strange]

32 minutes ago, beecee said:

While I agree and am fully aware of that situation, could it not be said that the SMBH at the center of most galaxies, does act as a sort of anchor for the rest of the galaxy?

I do remember a few years ago, coming across an article detailing the finding of a galaxy much larger [more disperse] then the MW galaxy, but without any SMBH at the core. The disperse nature of the BH [from memory] was attributed to it lacking any SMBH,

I was just reading an article on direct collapse black holes (https://www.scientificamerican.com/article/the-puzzle-of-the-first-black-holes/). One of the problems with supermassive black holes is how they could form. The idea here is that they form directly from the collapse of large cloud of gas (rather than from supernovae). They are then absorbed by a nearby galaxy. The energy released when the black hole absorbs material could heat up gas and affect star formation throughout the galaxy.

So there may well be effects beyond just the gravity.

 

[Janus]

58 minutes ago, beecee said:

While I agree and am fully aware of that situation, could it not be said that the SMBH at the center of most galaxies, does act as a sort of anchor for the rest of the galaxy?

I do remember a few years ago, coming across an article detailing the finding of a galaxy much larger [more disperse] then the MW galaxy, but without any SMBH at the core. The disperse nature of the BH [from memory] was attributed to it lacking any SMBH,

This is a bit and chicken and the egg question.  Did the galaxy form more dispersed due to the lack of SMBH, or did a SMBH not form because the material forming the galaxy was too diffuse?

[StringJunky]

24 minutes ago, Janus said:

This is a bit and chicken and the egg question.  Did the galaxy form more dispersed due to the lack of SMBH, or did a SMBH not form because the material forming the galaxy was too diffuse?

Is that the state of knowledge at the moment: undetermined?

[SimpleRick]

Well, that about wraps it up for that theory...

Thanks for the feedback, like I said I'm just a layman with a very rudimentary understanding of physics and cosmology. Was just something that came to me one day, just hope that it isn't like the Higgs-boson and in 50 years turns out it was something...

Although to answer Janus: the egg always came first... reptiles were laying eggs many millions of years before chickens had evolved...

Some very interesting notions here, might have to start reading a bit more about physics...

[Janus]

45 minutes ago, SimpleRick said:

Although to answer Janus: the egg always came first... reptiles were laying eggs many millions of years before chickens had evolved...

 

In the spirit of the question, the egg referred to is a chicken egg not just any kind of egg.

In this case, the answer depends on how you define "chicken egg".

We can assume, that somewhere along the chicken's ancestry, there is a bird that isn't yet what we would call a chicken. (where exactly one would draw the line in the genealogy between "chicken" and "non-chicken" is a bit of a grey area and would be pretty much an arbitrary choice). *

So let's say we've chosen our point of divergence between proto-chicken and chicken.   This mean a bird which is not quite a chicken, lays an egg that develops into what we would define as a chicken.   So now the question is:  Is the egg a chicken egg because it grows into a chicken, or is it a proto-chicken egg because it was lain by a proto-chicken?

Be that as it may, the term "chicken and egg question" has become to refer to any situation where we are unsure of the order of cause and effect,   regardless of any real answer there might be to the actual chicken and egg question.

* a creationist, on the other hand, would simply claim that the chicken was created by God first and then went on the lay the first chicken egg.

[J.C.MacSwell]

5 hours ago, Janus said:

In the spirit of the question, the egg referred to is a chicken egg not just any kind of egg.

In this case, the answer depends on how you define "chicken egg".

We can assume, that somewhere along the chicken's ancestry, there is a bird that isn't yet what we would call a chicken. (where exactly one would draw the line in the genealogy between "chicken" and "non-chicken" is a bit of a grey area and would be pretty much an arbitrary choice). *

So let's say we've chosen our point of divergence between proto-chicken and chicken.   This mean a bird which is not quite a chicken, lays an egg that develops into what we would define as a chicken.   So now the question is:  Is the egg a chicken egg because it grows into a chicken, or is it a proto-chicken egg because it was lain by a proto-chicken?

Be that as it may, the term "chicken and egg question" has become to refer to any situation where we are unsure of the order of cause and effect,   regardless of any real answer there might be to the actual chicken and egg question.

* a creationist, on the other hand, would simply claim that the chicken was created by God first and then went on the lay the first chicken egg.

There's gotta be a few that would simply claim He provided a nice nest of fertilized chicken eggs...

[MigL]

Interesting article Strange.
I didn't think it would be possible to have direct gas cloud collapse to a BH because at a certain size/pressure fusion burning would be ignited, stop further collapse, and drive off any more infalling gas.
I was only thinking in spherical terms, and not a rotating disk of gas.

Edited April 20, 2018 by MigL