Follow Slashdot stories on Twitter

 


Forgot your password?
Close
typodupeerror
×
Space Science

Black Hole Spewing Energy 16

Posted by timothy from the very-fabric-of-space dept.
dragoness.ai points to this story at space.com about some exciting news for black hole enthusiasts, writing "The scientists had a chance for the first time in history to observe energy coming out of a black hole."
This discussion has been archived. No new comments can be posted.

Black Hole Spewing Energy More

Black Hole Spewing Energy

Comments Filter:
  • "Never before have we seen energy extracted from a black hole," said co-author Christopher Reynolds of the University of Maryland, College Park. "We always see energy going in, not out."

    Except for Hawking radiation [colorado.edu] of course.

    • Re:Hawking (Score:3, Informative)

      by Yazeran ( 313637 )
      You are absolutely right, but Hawking radiation cannot transfer huge energies over short time. The effect of Hawking radiation is also scales inversely with the mass of the black hole, as the gravitational gradient is steeper near a small black hole than near a big one.

      Comparing Hawking radiation and this new magnetically induced energy transfer (if it exsists) is like comparing a candle light to the sun, Both create light but with different effect.

      Having discovered this method of energy transfer in the space close to a black hole might also be the key to explaining the huge energy jets observed from the centers of some galaxies (This is also mentioned in the original NASA article).


      Yours Yazeran


      Plan: To go to Mars one day with a hammer.

    • Re:Hawking (Score:3, Insightful)

      by krlynch ( 158571 )

      Except for Hawking radiation

      Actually, no. The quote was: "Never before have we seen energy extracted from a black hole". Since we have never seen the Hawking radiation emitted by any known black hole, this statement is true (we've also never seen energy extraction occur by the Penrose process); the Hawking temperature of any black hole currently observable would be lower than the cosmic background radiation temperature, and certainly orders of magnitude below the black hole's local thermal environment, that we would never have a prayer to observe the HR.

  • Some people have theorized that advanced civilizations might use black holes as a power source. Technological civilizations are always looking for something hotter to run their toys off of, and few things make as much heat as a massive black hole. Getting energy out of that much heat is easy, except for the problem of the huge gravity gradient and materials that can stand the temperature.
    • One of the cooler ways to get power from a black hole isn't by taking the energy directly. You just need a rapidly spinning hole with a wicked strong magnetic field. Viola, instant generator.
    • You have that backwards - smaller black holes have a steeper gravity gradient near the event horizon and they emit "hotter" radiation.

      But I thought that the real way an advanced civilization would use black holes to produce energy involved putting a matter stream into the "ergosphere," to transfer some of its rotational energy to the matter stream.
  • Rimmer: White-hole-spewing-time-engines-down-oxygen-low-su ggestions-please.

    Holly: What?
    • I hate to be a stickler but..

      RIMMER: (All in one breath) White hole. Spewing time. Engines dead. Air supply low. Advise please.

      HOLLY: Excuse me?

      RIMMER: (Again, as though attempting a world record on the most words spoken in one breath) White hole. Spewing time. Engines dead.--

      HOLLY: I can't understand a word you're saying.

      RIMMER: White.

      HOLLY: Yes.

      RIMMER: Hole.

      HOLLY: Right.

      RIMMER: Spewing.

      HOLLY: Yes.

      RIMMER: Time.

      HOLLY: With you.

      RIMMER: Engines dead.

      HOLLY: Oh.

      RIMMER: Air supply low.

      HOLLY: Ah.

      RIMMER: Advise please.

      HOLLY: Right

  • original NASA press release (Score:4, Informative)

    by rakerman ( 409507 ) on Wednesday October 24, 2001 @03:11AM (#2470940) Homepage Journal
    The original NASA science news release [nasa.gov] has way cooler video and audio about the black hole.
    • Yes, but the wideo is somewhat wrong.

      There should have been some visual red-shift observed at the two sides of the accretion disk.

      Having said that, the video does look cool.. :-)


      Yours Yazeran


      Plan: To go to Mars one day with a hammer.

  • Red Dwarf fans will recognise that this story's title should have been 'Black Hole Spewing Time. Engines Dead. Advice please'

  • My dilettante's knowledge of black holes says nothing comes out except some radiation whose name I forget, but which is generated by the simple expedient of having a pair of virtual particles generated near the event horizon, and one falls in while the other doesn't. Since the two can't then recombine to disappear, we get a spontaneously-generated random particle.

    (This is why one commentator maintains that causality fails near the event horizon. You could just as well get a desk [or a sperm whale] show up as some alpha particles. Of course, this is very roughly of the same probability as all the air molecules in your cube all moving to the left half for a second, leaving you in a vacuum. I wouldn't worry about it myself.)

    Anyway, since photons don't get out of a black hole, how is the alleged magnetism applied from within the dingus? Do space-time geodesics extend across the event horizon? (You know, all those neat graph lines in the diagrams showing how gravity warps space.) Does the spinning hole then drag them around, making it all work?

    I'd appreciate it if Carl Sagan's successor would speak up on this subject; thanks.

    • Black holes have no magnetic fields. If their parent stars had had magnetic fields, they would be radiated away upon formation of the black hole (see the "no hair" theorem).

      The material around a black hole in the accretion disk, however, can have a magnetic field. In fact, odds are pretty good that it will.
    • Maybe desks do tend to appear around a black hole, but tend to get torn apart. We'll need much better telescopes to find out.

      And I don't think I've had my room become a vacuum for a second. But I'm glad that our bodies can withstand vacuum for much longer than that.

Slashdot Top Deals

I tell them to turn to the study of mathematics, for it is only there that they might escape the lusts of the flesh. -- Thomas Mann, "The Magic Mountain"

Close