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Could dark matter consist of the supermassive black holes at the centers of galaxies?
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Inspired by this question about whether dark matter is matter, noting that dark matter tends to be clumped in galaxies near the center and less so on the edges, accepting that many (most?) galaxies have large black holes at their center, and theoretically, black holes have 'infinite' gravity, could black holes actually be the dark matter that holds galaxies together?
Put another way, how do we model the 'infinite' gravity of a black hole when considering the dynamics of a galaxy?
black-holes dark-matter galaxies galaxy-rotation-curve
edited 6 mins ago
Qmechanic♦
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asked 1 hour ago
CramerTV
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up vote
1
down vote
favorite
Inspired by this question about whether dark matter is matter, noting that dark matter tends to be clumped in galaxies near the center and less so on the edges, accepting that many (most?) galaxies have large black holes at their center, and theoretically, black holes have 'infinite' gravity, could black holes actually be the dark matter that holds galaxies together?
Put another way, how do we model the 'infinite' gravity of a black hole when considering the dynamics of a galaxy?
black-holes dark-matter galaxies galaxy-rotation-curve
edited 6 mins ago
Qmechanic♦
98.3k121731069
asked 1 hour ago
CramerTV
420310
Black holes don't have infinite gravity. Besides, the equations formulated for the rotation of the galaxies did not at all match with the force they should have possessed while turning, black holes at the center included.
– Curious Fish
1 hour ago
add a comment |Â
up vote
1
down vote
favorite
up vote
1
down vote
favorite
Inspired by this question about whether dark matter is matter, noting that dark matter tends to be clumped in galaxies near the center and less so on the edges, accepting that many (most?) galaxies have large black holes at their center, and theoretically, black holes have 'infinite' gravity, could black holes actually be the dark matter that holds galaxies together?
Put another way, how do we model the 'infinite' gravity of a black hole when considering the dynamics of a galaxy?
black-holes dark-matter galaxies galaxy-rotation-curve
edited 6 mins ago
Qmechanic♦
98.3k121731069
asked 1 hour ago
CramerTV
420310
Inspired by this question about whether dark matter is matter, noting that dark matter tends to be clumped in galaxies near the center and less so on the edges, accepting that many (most?) galaxies have large black holes at their center, and theoretically, black holes have 'infinite' gravity, could black holes actually be the dark matter that holds galaxies together?
Put another way, how do we model the 'infinite' gravity of a black hole when considering the dynamics of a galaxy?
black-holes dark-matter galaxies galaxy-rotation-curve
black-holes dark-matter galaxies galaxy-rotation-curve
edited 6 mins ago
Qmechanic♦
98.3k121731069
asked 1 hour ago
CramerTV
420310
edited 6 mins ago
Qmechanic♦
98.3k121731069
asked 1 hour ago
CramerTV
420310
edited 6 mins ago
Qmechanic♦
98.3k121731069
edited 6 mins ago
Qmechanic♦
98.3k121731069
edited 6 mins ago
Qmechanic♦
98.3k121731069
98.3k121731069
asked 1 hour ago
CramerTV
420310
asked 1 hour ago
CramerTV
420310
asked 1 hour ago
CramerTV
420310
420310
Black holes don't have infinite gravity. Besides, the equations formulated for the rotation of the galaxies did not at all match with the force they should have possessed while turning, black holes at the center included.
– Curious Fish
1 hour ago
add a comment |Â
Black holes don't have infinite gravity. Besides, the equations formulated for the rotation of the galaxies did not at all match with the force they should have possessed while turning, black holes at the center included.
– Curious Fish
1 hour ago
Black holes don't have infinite gravity. Besides, the equations formulated for the rotation of the galaxies did not at all match with the force they should have possessed while turning, black holes at the center included.
– Curious Fish
1 hour ago
Black holes don't have infinite gravity. Besides, the equations formulated for the rotation of the galaxies did not at all match with the force they should have possessed while turning, black holes at the center included.
– Curious Fish
1 hour ago
add a comment |Â
2 Answers
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Do the black holes at the center of galaxies account for the experimental results that prompted the introduction of dark matter? No
The primary piece of evidence that originally sparked the idea of dark matter is the rotation curve of galaxies. We found that galaxies don't rotate like the luminous matter suggests it should rotate. Specifically, given some estimates of enclosed mass at some radius from the center of a given galaxy, galaxies were found to rotate faster at given radii than expected. In other words, the luminous matter didn't seem to account for all the mass within any given radius. This lead to the idea that galaxies are permeated by a "dark matter" that isn't luminous. For this idea to work though, the dark matter needs to permeate the galaxy, it can't all be concentrated at the center of the galaxy like the central black hole (to really explain why this is one would have to get into a bit more details into rotation curves and how the expectations differ from observations).
Other pieces of evidence, like the dynamics which occurs when two galactic clusters collide also wouldn't be accounted for by galactic central black holes. See e.g. the bullet cluster.
Is it possible that the dark matter is made up of many smaller black holes? Possible, but not likely.
At one point in time, conjecture that the dark matter consisted of (moderate sized) black holes and other compact objects which have low luminosity. This was the MACHO theory (MAssive Compact Halo Objects). But this theory has largely fallen out of favor.
As Ben points out in a comment, another candidate might be primordial black holes, but their abundance appears to be too low to be good candidates at this time.
answered 1 hour ago
enumaris
3,1131419
add a comment |Â
up vote
2
down vote
Black holes don't have "infinite gravity". The only "infinite thing" associated with a black hole is that the value of the Reimann curvature tensor at the center of a (Schwarzschild or Reissner-Nordstrom) black hole is infinity according to general relativity. But we know that general relativity is not supposed to be a reliable theory near the center of the black hole (where the quantum gravity effects presumably take over)--and thus, even this single infinitely large quantity that we can associate with a black hole is also not really reliably infinite.
Anyway, even if the curvature were infinitely large at the center of the black hole, the effects of gravitation of the black hole are always finite at every point (inside and outside of the black hole) except for the center itself. In fact, according to the Birkhoff theorem (for spherically symmetric stationary black holes), the gravitational effects outside the event horizon cannot be identified as any different from the same of an equally massive spherically symmetric non-black object (which would be centered at the center of the black hole)! So, for example, if the Sun collapsed to a black hole, the Earth (or Mercury or anything outside the surface of the Sun) wouldn't feel a thing as far as the gravitational effects are concerned. So, there is no such thing as "an infinite gravity of a black hole".
Now, dark matter is supposed to be distributed throughout the galaxy. There might be some density distribution I suppose but all of dark matter isn't centered at the center of the galaxy. If it were, we wouldn't find anomalies in the galactic rotation curves which led us to postulate dark matter in the first place! So, no, dark matter (at least that we observe throughout the galaxy) cannot be just some effect due to the black hole at the center of the galaxy.
answered 50 mins ago
Dvij Mankad
4,68022364
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
Do the black holes at the center of galaxies account for the experimental results that prompted the introduction of dark matter? No
The primary piece of evidence that originally sparked the idea of dark matter is the rotation curve of galaxies. We found that galaxies don't rotate like the luminous matter suggests it should rotate. Specifically, given some estimates of enclosed mass at some radius from the center of a given galaxy, galaxies were found to rotate faster at given radii than expected. In other words, the luminous matter didn't seem to account for all the mass within any given radius. This lead to the idea that galaxies are permeated by a "dark matter" that isn't luminous. For this idea to work though, the dark matter needs to permeate the galaxy, it can't all be concentrated at the center of the galaxy like the central black hole (to really explain why this is one would have to get into a bit more details into rotation curves and how the expectations differ from observations).
Other pieces of evidence, like the dynamics which occurs when two galactic clusters collide also wouldn't be accounted for by galactic central black holes. See e.g. the bullet cluster.
Is it possible that the dark matter is made up of many smaller black holes? Possible, but not likely.
At one point in time, conjecture that the dark matter consisted of (moderate sized) black holes and other compact objects which have low luminosity. This was the MACHO theory (MAssive Compact Halo Objects). But this theory has largely fallen out of favor.
As Ben points out in a comment, another candidate might be primordial black holes, but their abundance appears to be too low to be good candidates at this time.
answered 1 hour ago
enumaris
3,1131419
add a comment |Â
up vote
3
down vote
Do the black holes at the center of galaxies account for the experimental results that prompted the introduction of dark matter? No
The primary piece of evidence that originally sparked the idea of dark matter is the rotation curve of galaxies. We found that galaxies don't rotate like the luminous matter suggests it should rotate. Specifically, given some estimates of enclosed mass at some radius from the center of a given galaxy, galaxies were found to rotate faster at given radii than expected. In other words, the luminous matter didn't seem to account for all the mass within any given radius. This lead to the idea that galaxies are permeated by a "dark matter" that isn't luminous. For this idea to work though, the dark matter needs to permeate the galaxy, it can't all be concentrated at the center of the galaxy like the central black hole (to really explain why this is one would have to get into a bit more details into rotation curves and how the expectations differ from observations).
Other pieces of evidence, like the dynamics which occurs when two galactic clusters collide also wouldn't be accounted for by galactic central black holes. See e.g. the bullet cluster.
Is it possible that the dark matter is made up of many smaller black holes? Possible, but not likely.
At one point in time, conjecture that the dark matter consisted of (moderate sized) black holes and other compact objects which have low luminosity. This was the MACHO theory (MAssive Compact Halo Objects). But this theory has largely fallen out of favor.
As Ben points out in a comment, another candidate might be primordial black holes, but their abundance appears to be too low to be good candidates at this time.
answered 1 hour ago
enumaris
3,1131419
add a comment |Â
up vote
3
down vote
up vote
3
down vote
Do the black holes at the center of galaxies account for the experimental results that prompted the introduction of dark matter? No
The primary piece of evidence that originally sparked the idea of dark matter is the rotation curve of galaxies. We found that galaxies don't rotate like the luminous matter suggests it should rotate. Specifically, given some estimates of enclosed mass at some radius from the center of a given galaxy, galaxies were found to rotate faster at given radii than expected. In other words, the luminous matter didn't seem to account for all the mass within any given radius. This lead to the idea that galaxies are permeated by a "dark matter" that isn't luminous. For this idea to work though, the dark matter needs to permeate the galaxy, it can't all be concentrated at the center of the galaxy like the central black hole (to really explain why this is one would have to get into a bit more details into rotation curves and how the expectations differ from observations).
Other pieces of evidence, like the dynamics which occurs when two galactic clusters collide also wouldn't be accounted for by galactic central black holes. See e.g. the bullet cluster.
Is it possible that the dark matter is made up of many smaller black holes? Possible, but not likely.
At one point in time, conjecture that the dark matter consisted of (moderate sized) black holes and other compact objects which have low luminosity. This was the MACHO theory (MAssive Compact Halo Objects). But this theory has largely fallen out of favor.
As Ben points out in a comment, another candidate might be primordial black holes, but their abundance appears to be too low to be good candidates at this time.
answered 1 hour ago
enumaris
3,1131419
Do the black holes at the center of galaxies account for the experimental results that prompted the introduction of dark matter? No
The primary piece of evidence that originally sparked the idea of dark matter is the rotation curve of galaxies. We found that galaxies don't rotate like the luminous matter suggests it should rotate. Specifically, given some estimates of enclosed mass at some radius from the center of a given galaxy, galaxies were found to rotate faster at given radii than expected. In other words, the luminous matter didn't seem to account for all the mass within any given radius. This lead to the idea that galaxies are permeated by a "dark matter" that isn't luminous. For this idea to work though, the dark matter needs to permeate the galaxy, it can't all be concentrated at the center of the galaxy like the central black hole (to really explain why this is one would have to get into a bit more details into rotation curves and how the expectations differ from observations).
Other pieces of evidence, like the dynamics which occurs when two galactic clusters collide also wouldn't be accounted for by galactic central black holes. See e.g. the bullet cluster.
Is it possible that the dark matter is made up of many smaller black holes? Possible, but not likely.
At one point in time, conjecture that the dark matter consisted of (moderate sized) black holes and other compact objects which have low luminosity. This was the MACHO theory (MAssive Compact Halo Objects). But this theory has largely fallen out of favor.
As Ben points out in a comment, another candidate might be primordial black holes, but their abundance appears to be too low to be good candidates at this time.
answered 1 hour ago
enumaris
3,1131419
edited 1 hour ago
answered 1 hour ago
enumaris
3,1131419
answered 1 hour ago
enumaris
3,1131419
answered 1 hour ago
enumaris
3,1131419
3,1131419
add a comment |Â
add a comment |Â
up vote
2
down vote
Black holes don't have "infinite gravity". The only "infinite thing" associated with a black hole is that the value of the Reimann curvature tensor at the center of a (Schwarzschild or Reissner-Nordstrom) black hole is infinity according to general relativity. But we know that general relativity is not supposed to be a reliable theory near the center of the black hole (where the quantum gravity effects presumably take over)--and thus, even this single infinitely large quantity that we can associate with a black hole is also not really reliably infinite.
Anyway, even if the curvature were infinitely large at the center of the black hole, the effects of gravitation of the black hole are always finite at every point (inside and outside of the black hole) except for the center itself. In fact, according to the Birkhoff theorem (for spherically symmetric stationary black holes), the gravitational effects outside the event horizon cannot be identified as any different from the same of an equally massive spherically symmetric non-black object (which would be centered at the center of the black hole)! So, for example, if the Sun collapsed to a black hole, the Earth (or Mercury or anything outside the surface of the Sun) wouldn't feel a thing as far as the gravitational effects are concerned. So, there is no such thing as "an infinite gravity of a black hole".
Now, dark matter is supposed to be distributed throughout the galaxy. There might be some density distribution I suppose but all of dark matter isn't centered at the center of the galaxy. If it were, we wouldn't find anomalies in the galactic rotation curves which led us to postulate dark matter in the first place! So, no, dark matter (at least that we observe throughout the galaxy) cannot be just some effect due to the black hole at the center of the galaxy.
answered 50 mins ago
Dvij Mankad
4,68022364
add a comment |Â
up vote
2
down vote
Black holes don't have "infinite gravity". The only "infinite thing" associated with a black hole is that the value of the Reimann curvature tensor at the center of a (Schwarzschild or Reissner-Nordstrom) black hole is infinity according to general relativity. But we know that general relativity is not supposed to be a reliable theory near the center of the black hole (where the quantum gravity effects presumably take over)--and thus, even this single infinitely large quantity that we can associate with a black hole is also not really reliably infinite.
Anyway, even if the curvature were infinitely large at the center of the black hole, the effects of gravitation of the black hole are always finite at every point (inside and outside of the black hole) except for the center itself. In fact, according to the Birkhoff theorem (for spherically symmetric stationary black holes), the gravitational effects outside the event horizon cannot be identified as any different from the same of an equally massive spherically symmetric non-black object (which would be centered at the center of the black hole)! So, for example, if the Sun collapsed to a black hole, the Earth (or Mercury or anything outside the surface of the Sun) wouldn't feel a thing as far as the gravitational effects are concerned. So, there is no such thing as "an infinite gravity of a black hole".
Now, dark matter is supposed to be distributed throughout the galaxy. There might be some density distribution I suppose but all of dark matter isn't centered at the center of the galaxy. If it were, we wouldn't find anomalies in the galactic rotation curves which led us to postulate dark matter in the first place! So, no, dark matter (at least that we observe throughout the galaxy) cannot be just some effect due to the black hole at the center of the galaxy.
answered 50 mins ago
Dvij Mankad
4,68022364
add a comment |Â
up vote
2
down vote
up vote
2
down vote
Black holes don't have "infinite gravity". The only "infinite thing" associated with a black hole is that the value of the Reimann curvature tensor at the center of a (Schwarzschild or Reissner-Nordstrom) black hole is infinity according to general relativity. But we know that general relativity is not supposed to be a reliable theory near the center of the black hole (where the quantum gravity effects presumably take over)--and thus, even this single infinitely large quantity that we can associate with a black hole is also not really reliably infinite.
Anyway, even if the curvature were infinitely large at the center of the black hole, the effects of gravitation of the black hole are always finite at every point (inside and outside of the black hole) except for the center itself. In fact, according to the Birkhoff theorem (for spherically symmetric stationary black holes), the gravitational effects outside the event horizon cannot be identified as any different from the same of an equally massive spherically symmetric non-black object (which would be centered at the center of the black hole)! So, for example, if the Sun collapsed to a black hole, the Earth (or Mercury or anything outside the surface of the Sun) wouldn't feel a thing as far as the gravitational effects are concerned. So, there is no such thing as "an infinite gravity of a black hole".
Now, dark matter is supposed to be distributed throughout the galaxy. There might be some density distribution I suppose but all of dark matter isn't centered at the center of the galaxy. If it were, we wouldn't find anomalies in the galactic rotation curves which led us to postulate dark matter in the first place! So, no, dark matter (at least that we observe throughout the galaxy) cannot be just some effect due to the black hole at the center of the galaxy.
answered 50 mins ago
Dvij Mankad
4,68022364
Black holes don't have "infinite gravity". The only "infinite thing" associated with a black hole is that the value of the Reimann curvature tensor at the center of a (Schwarzschild or Reissner-Nordstrom) black hole is infinity according to general relativity. But we know that general relativity is not supposed to be a reliable theory near the center of the black hole (where the quantum gravity effects presumably take over)--and thus, even this single infinitely large quantity that we can associate with a black hole is also not really reliably infinite.
Anyway, even if the curvature were infinitely large at the center of the black hole, the effects of gravitation of the black hole are always finite at every point (inside and outside of the black hole) except for the center itself. In fact, according to the Birkhoff theorem (for spherically symmetric stationary black holes), the gravitational effects outside the event horizon cannot be identified as any different from the same of an equally massive spherically symmetric non-black object (which would be centered at the center of the black hole)! So, for example, if the Sun collapsed to a black hole, the Earth (or Mercury or anything outside the surface of the Sun) wouldn't feel a thing as far as the gravitational effects are concerned. So, there is no such thing as "an infinite gravity of a black hole".
Now, dark matter is supposed to be distributed throughout the galaxy. There might be some density distribution I suppose but all of dark matter isn't centered at the center of the galaxy. If it were, we wouldn't find anomalies in the galactic rotation curves which led us to postulate dark matter in the first place! So, no, dark matter (at least that we observe throughout the galaxy) cannot be just some effect due to the black hole at the center of the galaxy.
answered 50 mins ago
Dvij Mankad
4,68022364
edited 34 mins ago
answered 50 mins ago
Dvij Mankad
4,68022364
answered 50 mins ago
Dvij Mankad
4,68022364
answered 50 mins ago
Dvij Mankad
4,68022364
4,68022364
add a comment |Â
add a comment |Â
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Black holes don't have infinite gravity. Besides, the equations formulated for the rotation of the galaxies did not at all match with the force they should have possessed while turning, black holes at the center included.
– Curious Fish
1 hour ago