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Hundreds of Black Holes Roam Loose In Milky Way

Posted by samzenpus on from the Maximilian-and-old-bob dept.

sciencehabit writes "From Science: 'Astronomers suspect that hundreds of medium-sized black holes are roaming loose in the Milky Way. These rogues, according to a new study, are the orphaned central black holes of the many smaller galaxies that the Milky Way has swallowed over its billions of years of existence.'"

8 of 254 comments (clear)

  1. Gamma ray bursts and high energy cosmic rays by MichaelSmith · · Score: 5, Interesting

    I wonder if black holes could account for either of these things? Gamma rays would be released if a large mass hits a black hole. A cosmic ray could be accelerated if it passes too close to a black hole.

    --
    http://michaelsmith.id.au
  2. Nah, I call BS by DavidRawling · · Score: 3, Interesting

    Scenario. The Milky Way swallows a galaxy, and by extension, all the stars around the central black hole. Yet, the same gravity that causes the stars to amalgamate completely misses the biggest mass in that swallowed galaxy? Why would that make sense?

    1. Re:Nah, I call BS by MichaelSmith · · Score: 4, Interesting

      Scenario. The Milky Way swallows a galaxy, and by extension, all the stars around the central black hole. Yet, the same gravity that causes the stars to amalgamate completely misses the biggest mass in that swallowed galaxy? Why would that make sense?

      The only bit which I think is strange is that the black hole from the swallowed galaxy hangs around in our galaxy. It should have enough velocity to pass right through our galaxy and never come back. Most likely the captured stars would die of old age before they passed though our galaxy. Only red dwarfs would keep going because of their long life. Gas clouds in the captured galaxy would interact with our gas clouds. I think that is the only component which would really get captured.

      --
      http://michaelsmith.id.au
    2. Re:Nah, I call BS by Brown · · Score: 3, Interesting

      The Milky Way swallows a galaxy, and the swallowed galaxy's stars get added to the milky way, orbiting the galactic centre in the usual way. Presumably the same happens to the black hole - there's no reason why it should be sucked into the middle. Black holes will happily orbit around each other, as long as they're outside each other's event horizons.

    3. Re:Nah, I call BS by AlecC · · Score: 5, Interesting

      Because the galaxy is not a point mass. Most ordinary star/planet modelling is based on viewing each object as a sphere, which behaves as a point mass at the centre. But when you penetrate inside another body, as two galaxies do when they collide, this simplification no longer applies. Some of the mass of the "other" galaxy moves behind the penetrating galaxy, slowing it down rather than, as the point mass model would suggest, continuing to accelerate into the centre. In the simplest model, of inter-penetrating spheres, gravity no longer has an inverse square law but an inverse linear law. Of course, galaxies are not uniform spheres, and the modelling is much harder. However, it is widely accepted that when two galaxies collide, they merge and the vast majority of the mass forms a single galaxy - though clusters may be flung out. If the galaxies are of broadly similar masses, the distinctive spiral structure is wiped out and the merged result becomes an elliptical galaxy for a few hundred million years before the spiral structure re-establishes.

      Google "andromeda collisions" for simulations of the collision between our galaxy and the Andromeda galaxy in about 3 billion years.

      --
      Consciousness is an illusion caused by an excess of self consciousness.
    4. Re:Nah, I call BS by stonewallred · · Score: 4, Interesting

      What happens when two black holes actually intersect at their event horizons? Inquiring non-astrophysicists would like to know.

    5. Re:Nah, I call BS by beanyk · · Score: 3, Interesting

      Well for one thing, the "time moving slowly" thing is an observer-dependent effect. If you were the one falling into the hole, you wouldn't notice any real time lag at all [depending on the size of the hole -- and your personal oxygen supply, etc -- you might even survive crossing the horizon].

      But to a distant observer, your progress would look more and more gradual. Signals leaving you would also get more and more red-shifted, and eventually pass out of the visible spectrum. So a distant observer would never see you cross the horizon.

  3. Re:First swine flu, now loose-roaming black holes? by Nephrite · · Score: 5, Interesting

    Looks like everyone has already forgot the LHC...