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Milky Way Black Hole Could Reignite

Posted by kdawson on from the tinfoil-umbrellas-might-help dept.

sciencehabit sends us to Sciencemag.org for an account of a survey of nearby galaxies that points to the possibility that once-quiescent galactic nuclei could wake up and become active again. If the Milky Way's dormant black hole should become active, it could be bad news for life on Earth (and elsewhere in the neighborhood). The paper (PDF) is up on the arXiv.

8 of 117 comments (clear)

  1. Eye muss bee knew hear by sm62704 · · Score: 4, Informative

    Darn, and I never EVER rtfa, but the summary made it necessary. So for my fellow slashdotters who hate to RTFA, what they mean by "reignite" is to turn into a quasar. The way the black hole could turn into a quasar is for the galaxy to collide with another galaxy.

    I don't think we have anything to worry about. Nothing to see here (and if it happened, nobody to see it)

    --
    mcgrew's razor: Never attribute to stupidity that which can be explained by greedy self-interest
    1. Re:Eye muss bee knew hear by Dan+East · · Score: 5, Informative

      "The way the black hole could turn into a quasar is for the galaxy to collide with another galaxy."

      That's not what the article says:
      It's not understood what is causing the black holes to become newly active, because in most cases there is no evidence of collisions or mergers.

      --
      Better known as 318230.
    2. Re:Eye muss bee knew hear by DynaSoar · · Score: 2, Informative

      Darn, and I never EVER rtfa, but the summary made it necessary. So for my fellow slashdotters who hate to RTFA, what they mean by "reignite" is to turn into a quasar. The way the black hole could turn into a quasar is for the galaxy to collide with another galaxy.

      I don't think we have anything to worry about. Nothing to see here (and if it happened, nobody to see it) Obviously there is something to see here. Us. Our sun was a member of a galaxy that was absorbed by the Milky Way. The evidence is in the fact that we do not orbit the center of this galaxy in the plane of its arms, but rather perform a wave-like motion alternatively above and below the center plane, passing through the plane in between peaks. A galactic collision could produce the effect noted in TFA, while simultaneously increasing interstellar gas and dust cloud densities, protecting the outer stars from the radiation produced (as well as forcing new star production). So much for "It's not understood what is causing the black holes to become newly active, because in most cases there is no evidence of collisions or mergers." We are the evidence, and our existence is evidence the result need not be as dangerous as stated.

      While we are well out from the center, we'd be in periods of more danger from the radiation than those stars native to this galaxy, due to our cyclic motion going outside the galactic plane. More danger, yes, but whether the danger is significant and whether other side effects might dampen the effects, are factors not addressed.

      In any case, reignition of an active galactic core is due to an increase in infalling matter, and that's obviously not necessarily due to galactic collision. We can't see the details of the matter near the core, so we can't tell whether there's clumps that can fall in en mass, or whether it's relatively smooth and unlikely to cause bursts of activity.
      --
      "I may be synthetic, but I'm not stupid." -- Bishop 341-B
  2. No evidence for "re-ignition" by random+coward · · Score: 4, Informative

    Quick summary of TFA: Scientists observe that the black holes at the center of galaxies were Quasars on far away galaxies. The one at the center of the Milky Way and other nerby galaxies were observed to not be Quasars. So they theorised that the black holes initially are quasars after galaxy formation, and they run out of fuel. New observations show that nearby galaxies do in fact have quasars. A scientist conjectured that it re-ignited. Better conjecture may be that the fuel source of those blackhole-quasars is more variable than previously thought.

  3. Re:Axis of Rotation by Tenebrousedge · · Score: 2, Informative

    Probably we wouldn't see a thing...

    --
    Those who advocate genocide deserve every protection afforded by law, and none afforded by common human decency.
  4. Re:20 to 40%? Reignite? by HTH+NE1 · · Score: 3, Informative

    How could it be verified that despite the lack of a recent collision with another galaxy, these particular phenomenon were at some point dormant like ours, then reignited? By the velocity vectors of surrounding matter affected by the blast? A collision would give the local matter directionality whereas a spontaneous reignition would send matter out in all directions uniformly.

    Haven't you watched CSI: Stellar Cartography Unit?
    --
    Oh, say does that Star-Spangled Banner entwine / The myrtle of Venus with Bacchus's vine?
  5. Feed Me by iamlucky13 · · Score: 3, Informative

    For a black hole to be active, it needs stuff falling into it...gas, dust, stars if you're unlucky. The stuff heats up to an extraordinary temperature due to friction as it falls in. To be hazardous at our distance of 25,000 light-years from the galactic center, it has to be quite a bit of matter falling in for a harmful intensity of radiation.

    Our galaxy's black hole, Sagittarius-A, is not considered active, although it does have some weak emissions, primarily at harmless infrared and radio wavelengths consistent with a very small accretion disc. The nearest star to the black hole is estimated to be about 70 times as far away from it as it would need to be for the gravitational forces to remove significant amounts of material from the star. It also has an orbital period of 15 years, so it would take a long time and a significant perturbance to fall significantly close. It doesn't seem likely at all that it would become active in the foreseeable future.

  6. Re:Still not getting it ... by Stevecrox · · Score: 2, Informative

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

    Quasars are an effect created by the supermassive black holes at the centre of each galaxy, these black holes consume tremendous amounts of mater (something like 10 sun masses a year) the more solar masses they consume the brighter they are. Obviously there is only so much material than can be pulled in by the supermassive black hole, eventually all the material is either ejected as high intensity engery (the quaser pulses we can observe) or consumed by the black hole.

    The article mentions that astronomers have discovered galaxies with quasars which are old enough that the matter orbiting the black hole should have been used up. The current scientific hypothisis for old galaxies with quasars, is that the collision of two galaxies can generate new material which is pulled in by the supermassive black hole (thus supplying the matter to generate a quasar.) These older galaxies don't show any signs of recent collision and so the question of how the black holes in the centre are getting enough matter to generate a quasar needs to be asked. Since scientists don't know why there are quasars on these older galaxies they seem to be assuming that something else is causing new matter to be sucked into a galaxies supermassive black hole. The articles twist is this could potentially happen in our own galaxy, potentially killing us all.