Dormant Black Holes

• by bluemagi

  Hi, Could someone please tell me if there are any articles with information on dormant or sleeping blackholes or even books. Cheers, bluemagi

  Posted August 20, 2017 11:56 PM

• by Budgieye moderator

  I suppose when black holes are dormant, all you can do is measure how massive they are, or look for radio lobes or voorwerps showing past activity.

  3.7 Black holes and SMBH (Super Massive Black Holes) https://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ0000wrb?page=3&comment_id=53d8b91b0d43f77bb6000f96

  Posted August 21, 2017 7:53 AM

• by bluemagi

  http://www.abc.net.au/news/science/2017-02-07/nasa-chandra-binge-eating-black-hole-devours-massive-star/8247380. What I am trying to find out is what would happen if a supermassive black hole passes by a galaxy? It a long hypothesis so I won't go into it now. Thanks Budgieye. Cheers , bluemagi

  Posted August 21, 2017 8:20 AM

• by bluemagi

  https://phys.org/news/2016-06-dormant-black-hole-star-x-ray.html. This is another interesting article on dormant black holes.Cheers bluemagi

  Posted August 21, 2017 8:58 AM

• by Budgieye moderator

  Black holes are only a small part of a galaxy, even big ones are only about 1/1000 of the mass of the galaxy.

  Posted August 21, 2017 9:59 AM

• by bluemagi

  Yes I know they are only a small part. Anyway I'll continue my search for answers. Thanks, bluemagi

  Posted August 21, 2017 10:58 AM

• by ccardamone scientist

  That's a great question about a black hole. In essence a black hole is just a gravitational object (very compact), but still just a very small massive object. There are lots of stellar remnant black holes in any normal galaxy, including our own. There are moderately small (several 10s of solar masses) and are the remains of massive stars that lived fast and died in a supernova. There are also intermediate mass black holes (although there is an active debate about how common they might be & how they are formed - http://www.skyandtelescope.com/astronomy-news/best-evidence-yet-for-an-intermediate-mass-black-hole/). And finally the supermassive black holes, that reside in the centers of massive galaxies.

  Black holes without any stars, gas or dust nearby are dormant - have no active accretion because there is nothing around to accrete. When matter comes to close, like when you have a binary system whose partner evolves into a supergiant or you have a star whose orbit takes it too close to the black hole, it 'turns on' and becomes active.

  When 2 galaxies merge, their black holes get stirred up just like their stars, and the massive black holes - being the most massive objects in their gravitational hosts (the galaxies), sink to the center of the newly merged galaxy. The other black holes get new orbits, just like the stars that were part of the two galaxies pre-mergers. (Here's a pretty video of this - https://www.youtube.com/watch?v=_FlGiqPdbx8)

  Now if we did a though experiment of a super massive black hole, let's go crazy and say it's billion times the mass of the sun AND is traveling alone in space (this would be highly unlikely because it would need a very dense region, like the center of a super massive galaxy, probably one residing in a massive cluster, to form). If this black hole happened to wander near a galaxy, it might orbit happily at some distance from the center of the galaxy, and eventually loose some gravitational potential energy (through interactions) and sink to the center of the galaxy. There it would merge with the BH at the galaxy's center. (Pretty simulation of BH merger - https://www.ligo.caltech.edu/video/ligo20160211v3)

  Hope this helps to answer your question...
  Carie

  Posted August 22, 2017 7:35 PM

• by bluemagi

  Excellent ! Thank you very much. Bluemagi

  Posted August 23, 2017 4:31 AM