Comments on: Galaxies get fat and weird along with their black holes http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/ Wed, 21 Nov 2012 15:12:45 +0000 hourly 1 http://wordpress.org/?v=3.4.2 By: Torbjörn Larsson, OM http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91848 Torbjörn Larsson, OM Thu, 05 Jun 2008 21:16:37 +0000 http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91848 <blockquote> does anyone know if the blackholes in the center combine or do they orbit each other in the core of the galaxy? </blockquote> I thought they were usually merging as galaxies combine to grow from the big bang on and most galaxies now are thought to have central massive holes, as <a href="http://www.sciencedaily.com/releases/2005/02/050212090148.htm" rel="nofollow">this paper</a> suggests. Also, I believe I have seen simulations (perhaps without dynamic friction) where at least one black hole can be ejected, <a href="http://arxiv.org/abs/0802.2058" rel="nofollow">this paper</a> suggests.

does anyone know if the blackholes in the center combine or do they orbit each other in the core of the galaxy?

I thought they were usually merging as galaxies combine to grow from the big bang on and most galaxies now are thought to have central massive holes, as this paper suggests. Also, I believe I have seen simulations (perhaps without dynamic friction) where at least one black hole can be ejected, this paper suggests.

]]> By: davidlpf http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91847 davidlpf Wed, 04 Jun 2008 23:35:48 +0000 http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91847 Take the Earth and moon, the moon actually does not orbit the center of the Earth but it orbits the center of mass which is just below the the surface of the Earth. If you scale it up to two stars that are about the same mass the center of mass is located more towards the center of the system. Two blackholes out side their event horizons are just massives stars so they would orbit each other their center of mass. Now lets start with a blackhole all alone in space and then another blackhole close so close that it starts orbiting the first blackhole. The second blackhole will start to "tug" at the first blackhole increasing its kinetic energy but since energy most be conserved the energy for the second Blackhole decreases. As time goes by they eventually start orbiting each other. That was my origional thought on it, does anyone know if the blackholes in the center combine or do they orbit each other in the core of the galaxy? Now increase the masses to a billion times as the sun also add in all the stars, and interstellar medium for dynamic drag effect and you get probably what really goes on with the blackholes as the galaxy combine. Take the Earth and moon, the moon actually does not orbit the center of the Earth but it orbits the center of mass which is just below the the surface of the Earth. If you scale it up to two stars that are about the same mass the center of mass is located more towards the center of the system. Two blackholes out side their event horizons are just massives stars so they would orbit each other their center of mass. Now lets start with a blackhole all alone in space and then another blackhole close so close that it starts orbiting the first blackhole. The second blackhole will start to “tug” at the first blackhole increasing its kinetic energy but since energy most be conserved the energy for the second Blackhole decreases.
As time goes by they eventually start orbiting each other. That was my origional thought on it, does anyone know if the blackholes in the center combine or do they orbit each other in the core of the galaxy?
Now increase the masses to a billion times as the sun also add in all the stars, and interstellar medium for dynamic drag effect and you get probably what really goes on with the blackholes as the galaxy combine.

]]> By: davidlpf http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91846 davidlpf Wed, 04 Jun 2008 21:20:23 +0000 http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91846 Irishman sorry, but having Nathan coming in here commenting somthing is Startrek physics because it does not agree with he thinks is more then a little insulting. I may have something else say either tomorrow or next day. As I implied I am not an academic and work 9 to 5 job so it may it take to explain it better. Tom with that info from Mike Brotherton and wikipedia it makes sense to me the kinetic energy would be lost through friction with dust in the ISM. Nathan you really should learn to better deal with people. I think you were here on a earlier post saying that the BA did not how to read a graph and a paper about autism because he did not have degree in biology. Irishman sorry, but having Nathan coming in here commenting somthing is Startrek physics because it does not agree with he thinks is more then a little insulting. I may have something else say either tomorrow or next day. As I implied I am not an academic and work 9 to 5 job so it may it take to explain it better.

Tom with that info from Mike Brotherton and wikipedia it makes sense to me the kinetic energy would be lost through friction with dust in the ISM.

Nathan you really should learn to better deal with people. I think you were here on a earlier post saying that the BA did not how to read a graph and a paper about autism because he did not have degree in biology.

]]> By: Tom Marking http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91845 Tom Marking Wed, 04 Jun 2008 21:01:36 +0000 http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91845 "Dynamical friction is the most likely effect to bring the black holes together." O.K. There's an explanation that's starting to make sense. According to the Wikipedia article the dynamical friction force is proportional to the square of the black hole mass which means it's quite large for supermassive black holes. Mike, thanks for the explanation. Cheers. “Dynamical friction is the most likely effect to bring the black holes together.”

O.K. There’s an explanation that’s starting to make sense. According to the Wikipedia article the dynamical friction force is proportional to the square of the black hole mass which means it’s quite large for supermassive black holes.

Mike, thanks for the explanation. Cheers.

]]> By: Torbjörn Larsson, OM http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91844 Torbjörn Larsson, OM Wed, 04 Jun 2008 19:10:48 +0000 http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91844 D'oh! Sorry about the tag error, as well as the language mistake. Feels like nap time. D’oh! Sorry about the tag error, as well as the language mistake. Feels like nap time.

]]> By: Torbjörn Larsson, OM http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91843 Torbjörn Larsson, OM Wed, 04 Jun 2008 19:04:07 +0000 http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91843 Mike Brotherton, thanks for the explanations. <a href="http://www.eurekalert.org/pub_releases/2008-06/ciot-lop060208.php" rel="nofollow">LIGO set a limit on gravity waves energy loss>/a>: <blockquote> Michael Landry adds, "These results strongly imply that no more than 4 percent of the pulsar's energy loss is due to gravitational radiation. The remainder of the loss must be due to other mechanisms, such as a combination of electromagnetic radiation generated by the rapidly rotating magnetic field of the pulsar and the emission of high-velocity particles into the nebula." </blockquote></a> Mike Brotherton, thanks for the explanations.

LIGO set a limit on gravity waves energy loss>/a>:

Michael Landry adds, “These results strongly imply that no more than 4 percent of the pulsar’s energy loss is due to gravitational radiation. The remainder of the loss must be due to other mechanisms, such as a combination of electromagnetic radiation generated by the rapidly rotating magnetic field of the pulsar and the emission of high-velocity particles into the nebula.”

]]> By: Irishman http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91842 Irishman Wed, 04 Jun 2008 18:26:43 +0000 http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91842 Tom Marking said: > Now, replace the wing with a black hole. Do the air molecules rebound off it? Nope. There is no solid surface to rebound off of. Once they pass the event horizon they get sucked into the singularity. Maybe they cause some change in the linear momentum of the singularity but it would probably be offset by molecules falling into the event horizon on the back side. Why would the front side and back side balance? The black hole clears its path of material, correct? So you have a homogenous (rough approximation) field on three sides and an empty path behind. Now there may be fall in from entrainment or whatever, but is the back going to see and equal amount of matter fall in? No. Ergo, the imbalance in matter added to the front vs the back. So how does this slow the black hole? How about momentum transfer. The totally inelastic collision (black hole absorbs entire momentum) creates a drag. Nathan Meyers said: > I could imagine that extracting a fair bit of energy after a few billion passes, but why didn’t Mike say so? Because astronomical events operate on huge timescales, so that's the default assumption? davidlpf said: > Nathan get thee to some first year physics books. While I appreciate the simplicity of this response, it would perhaps be more productive to either attempt a layman's explanation or find a link to something online related to the topic. If this material is truly as basic as you state, that shouldn't be hard to come up with. > I have better things to waste my time on then you. Fair enough, but there are other people reading the thread who might benefit from at least a cursory explanation. Of course Mike Brotherton has replied. Tom Marking said:
> Now, replace the wing with a black hole. Do the air molecules rebound off it? Nope. There is no solid surface to rebound off of. Once they pass the event horizon they get sucked into the singularity. Maybe they cause some change in the linear momentum of the singularity but it would probably be offset by molecules falling into the event horizon on the back side.

Why would the front side and back side balance? The black hole clears its path of material, correct? So you have a homogenous (rough approximation) field on three sides and an empty path behind. Now there may be fall in from entrainment or whatever, but is the back going to see and equal amount of matter fall in? No. Ergo, the imbalance in matter added to the front vs the back. So how does this slow the black hole? How about momentum transfer. The totally inelastic collision (black hole absorbs entire momentum) creates a drag.

Nathan Meyers said:
> I could imagine that extracting a fair bit of energy after a few billion passes, but why didn’t Mike say so?

Because astronomical events operate on huge timescales, so that’s the default assumption?

davidlpf said:
> Nathan get thee to some first year physics books.

While I appreciate the simplicity of this response, it would perhaps be more productive to either attempt a layman’s explanation or find a link to something online related to the topic. If this material is truly as basic as you state, that shouldn’t be hard to come up with.

> I have better things to waste my time on then you.

Fair enough, but there are other people reading the thread who might benefit from at least a cursory explanation.

Of course Mike Brotherton has replied.

]]> By: Mike Brotherton http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91841 Mike Brotherton Wed, 04 Jun 2008 07:27:00 +0000 http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91841 "BTW, going from left-to-right and then top-to-bottom when I look at the 29 galaxies the only ones which show obvious signs of something weird happening structure-wise are: 4, 5, 7, 12, 14, and 20. The rest look like fairly typical galaxies." It's true that there are a few that are pretty normal looking, but many that don't look too weird still show more subtle signs like asymmetries, faint tidal tails, shell structures, etc., characteristic of mergers or other interactions. We'll be looking to quantify these in the near future. “BTW, going from left-to-right and then top-to-bottom when I look at the 29 galaxies the only ones which show obvious signs of something weird happening structure-wise are: 4, 5, 7, 12, 14, and 20. The rest look like fairly typical galaxies.”

It’s true that there are a few that are pretty normal looking, but many that don’t look too weird still show more subtle signs like asymmetries, faint tidal tails, shell structures, etc., characteristic of mergers or other interactions. We’ll be looking to quantify these in the near future.

]]> By: Mike Brotherton http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91840 Mike Brotherton Wed, 04 Jun 2008 07:25:08 +0000 http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91840 "Mike Brotherton above mentioned the energy dissipation mechanism, “gravitational radiation”. Merging black holes are one of the few phenomena thought to produce sufficient gravitational radiation to be seen by current gravity wave detecting technology, although I haven’t heard that they’ve “seen” anything like that yet." Just before the press conference, Steve Maran announced to everyone that LIGO was going to be announcing a gravitational wave detection from the crab nebula. Haven't seen that story break officially yet, but I haven't looked today. “Mike Brotherton above mentioned the energy dissipation mechanism, “gravitational radiation”. Merging black holes are one of the few phenomena thought to produce sufficient gravitational radiation to be seen by current gravity wave detecting technology, although I haven’t heard that they’ve “seen” anything like that yet.”

Just before the press conference, Steve Maran announced to everyone that LIGO was going to be announcing a gravitational wave detection from the crab nebula. Haven’t seen that story break officially yet, but I haven’t looked today.

]]> By: Mike Brotherton http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91839 Mike Brotherton Wed, 04 Jun 2008 07:23:08 +0000 http://blogs.discovermagazine.com/badastronomy/2008/06/02/galaxies-get-fat-and-weird-along-with-their-black-holes/#comment-91839 "Mike: You started this. What is supposed to strip each black hole of enough energy to get it into a close-enough orbit with the other for gravitational radiation to amount to anything?" I was off visiting local family this evening. Dynamical friction is the most likely effect to bring the black holes together. This is a subtle effect involving how a gravitating mass brings stars closer to it as it passes, and since they are closer when it leaves, they exert an extra retarding force. This dynamical friction can be very effective. Ah, there's actually a wiki article: http://en.wikipedia.org/wiki/Dynamical_friction “Mike: You started this. What is supposed to strip each black hole of enough energy to get it into a close-enough orbit with the other for gravitational radiation to amount to anything?”

I was off visiting local family this evening.

Dynamical friction is the most likely effect to bring the black holes together. This is a subtle effect involving how a gravitating mass brings stars closer to it as it passes, and since they are closer when it leaves, they exert an extra retarding force. This dynamical friction can be very effective.

Ah, there’s actually a wiki article:

http://en.wikipedia.org/wiki/Dynamical_friction

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