Columbia: Tens of Thousands of Black Holes Exist in Milky Way’s Center

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bystander
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Columbia: Tens of Thousands of Black Holes Exist in Milky Way’s Center

Post by bystander » Wed Apr 18, 2018 2:41 am

New Study Suggests Tens of Thousands of Black Holes Exist in Milky Way’s Center
Columbia University | 2018 Apr 04
A Columbia University-led team of astrophysicists has discovered a dozen black holes gathered around Sagittarius A* (Sgr A*), the supermassive black hole in the center of the Milky Way Galaxy. The finding is the first to support a decades-old prediction, opening up myriad opportunities to better understand the universe.

"Everything you'd ever want to learn about the way big black holes interact with little black holes, you can learn by studying this distribution,” said Columbia Astrophysicist Chuck Hailey, co-director of the Columbia Astrophysics Lab and lead author on the study. “The Milky Way is really the only galaxy we have where we can study how supermassive black holes interact with little ones because we simply can't see their interactions in other galaxies. In a sense, this is the only laboratory we have to study this phenomenon." ...

A density cusp of quiescent X-ray binaries in the central parsec of the Galaxy - Charles J. Hailey et al
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Re: CXC: Black Hole Bounty Captured in the Milky Way Center

Post by bystander » Wed May 09, 2018 7:38 pm

Sgr A* Swarm: Black Hole Bounty Captured in the Milky Way Center
NASA | MSFC | SAO | Chandra X-ray Observatory | 2018 May 09
Click to view full size image 1 or image 2
Credit: NASA/CXC/Columbia Univ./C. Hailey et al.
Astronomers have discovered evidence for thousands of black holes located near the center of our Milky Way galaxy using data from NASA's Chandra X-ray Observatory.

This black hole bounty consists of stellar-mass black holes, which typically weigh between five to 30 times the mass of the Sun. These newly identified black holes were found within three light years — a relatively short distance on cosmic scales — of the supermassive black hole at our Galaxy's center known as Sagittarius A* (Sgr A*).

Theoretical studies of the dynamics of stars in galaxies have indicated that a large population of stellar mass black holes — as many as 20,000 — could drift inward over the eons and collect around Sgr A*. This recent analysis using Chandra data is the first observational evidence for such a black hole bounty.

A black hole by itself is invisible. However, a black hole — or neutron star — locked in close orbit with a star will pull gas from its companion (astronomers call these systems "X-ray binaries"). This material falls into a disk and heats up to millions of degrees and produces X-rays before disappearing into the black hole. Some of these X-ray binaries appear as point-like sources in the Chandra image. ...

A Density Cusp of Quiescent X-ray Binaries in the Central Parsec of the Galaxy - Charles J. Hailey et al
Related paper:

An Overabundance of Black Hole X-Ray Binaries in the Galactic Center from Tidal Captures - A. Generozov et al
Last edited by bystander on Sat May 26, 2018 2:13 pm, edited 1 time in total.
Reason: added MNRAS link
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Re: CXC: Black Hole Bounty Captured in the Milky Way Center

Post by MarkBour » Wed May 09, 2018 8:37 pm


Theoretical studies of the dynamics of stars in galaxies have indicated that a large population of stellar mass black holes — as many as 20,000 — could drift inward over the eons and collect around Sgr A*.

Why would they do that?
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Re: CXC: Black Hole Bounty Captured in the Milky Way Center

Post by Chris Peterson » Wed May 09, 2018 9:19 pm

MarkBour wrote:
Wed May 09, 2018 8:37 pm

Theoretical studies of the dynamics of stars in galaxies have indicated that a large population of stellar mass black holes — as many as 20,000 — could drift inward over the eons and collect around Sgr A*.

Why would they do that?
A process called dynamical friction. Basically, black holes alter the orbits of stars and other matter they encounter, resulting in a sort of wake behind them. This produces an asymmetric gravitational force that removes orbital angular momentum from the black hole, causing its orbit to get smaller.

This is a very slow process, but there's a lot of time for it to happen. Of course, the closer a black hole gets to the center, the greater the surrounding mass density, and the faster the process goes.
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Re: CXC: Black Hole Bounty Captured in the Milky Way Center

Post by MarkBour » Wed May 09, 2018 11:52 pm

Chris Peterson wrote:
Wed May 09, 2018 9:19 pm
MarkBour wrote:
Wed May 09, 2018 8:37 pm

Theoretical studies of the dynamics of stars in galaxies have indicated that a large population of stellar mass black holes — as many as 20,000 — could drift inward over the eons and collect around Sgr A*.

Why would they do that?
A process called dynamical friction. Basically, black holes alter the orbits of stars and other matter they encounter, resulting in a sort of wake behind them. This produces an asymmetric gravitational force that removes orbital angular momentum from the black hole, causing its orbit to get smaller.

This is a very slow process, but there's a lot of time for it to happen. Of course, the closer a black hole gets to the center, the greater the surrounding mass density, and the faster the process goes.
Interesting! If I understand the concept correctly, it is that larger mass bodies will tend to migrate inward if there are lots of bodies present, not that there is anything special about black holes going on here. I was wondering about gravitational waves, but this effect, as you described, seems to be predictable simply by treating the stellar mass black holes as classical point masses and working out the motions with classical gravitational physics.

I wonder if a situation such as Jupiter versus our asteroid belt fits this scenario.
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Re: CXC: Black Hole Bounty Captured in the Milky Way Center

Post by neufer » Thu May 10, 2018 12:08 am

MarkBour wrote:
Wed May 09, 2018 11:52 pm
Chris Peterson wrote:
Wed May 09, 2018 9:19 pm

A process called dynamical friction. Basically, black holes alter the orbits of stars and other matter they encounter, resulting in a sort of wake behind them. This produces an asymmetric gravitational force that removes orbital angular momentum from the black hole, causing its orbit to get smaller.

This is a very slow process, but there's a lot of time for it to happen. Of course, the closer a black hole gets to the center, the greater the surrounding mass density, and the faster the process goes.
Interesting! If I understand the concept correctly, it is that larger mass bodies will tend to migrate inward if there are lots of bodies present, not that there is anything special about black holes going on here. I was wondering about gravitational waves, but this effect, as you described, seems to be predictable simply by treating the stellar mass black holes as classical point masses and working out the motions with classical gravitational physics.

I wonder if a situation such as Jupiter versus our asteroid belt fits this scenario.
The total mass of the asteroid belt would have to be a significant fraction of Jupiter's mass...which it isn't.

[Dynamical friction is simply another example where for entropy to increase (which it must)
kinetic energy must be transferred from the most massive bodies to the least massive bodies.

A thermalized bath of elastically colliding particles will equalize the particle
kinetic energies such that the velocities vary as square root of (E/m).]
Art Neuendorffer