5 ms·

I know next to nothing on black holes/star formation and astronomy in general, but isn't this a big deal? I thought a pretty big defining factor of black holes

by belval 5y ago

I know next to nothing on black holes/star formation and astronomy in general, but isn't this a big deal? I thought a pretty big defining factor of black holes was that nothing (not even light!) ever escaped it?

uoaei 5y ago
It is definitely an unusual observation, but I don't think it's really that big of a deal. A strong gravitational field would pull matter closer together, possibly kick-starting the fusion process if the energy density gets high enough in a certain region. If you asked an astrophysicist what would happen to a massive dust and gas cloud near a black hole, star formation would be 2 or 3 on the list that they rattle off. > But the gentler outflow of gas from the black hole in Henize 2-10 is compressed just enough to facilitate star formation. It's a Goldilocks thing. Black hole is strong enough to have a significant gravity, but weak enough that the shell of hot dense matter it harbors doesn't completely obliterate everything that falls toward it.
kadoban 5y ago
This is not evidence that anything has escaped the event horizon of a black hole. That _would_ be huge news (also pretty ~impossible, but still). This is just the region _near_ a black hole doing some star formation. Which is cool, but also :shrug:.
davesque 5y ago
I don't think this finding challenges any of those assumptions. I think the explanation was that the relativistic jet for smaller blackholes located at galaxy centers is moving slow enough that the compressive effects of the jet are not overcome by the speed. The compression therefore helps with star formation since the jet isn't moving fast enough to disrupt that process.
tejtm 5y ago
Might help to think of it as more of a reprieve. In that the star itself or its remains will still likely end up inside the black holes Schwarzschild radius never to be seen again except as Hawking radiation till the BH evaporates. That the environment directly outside a BH is energetic enough fling some stuff "up" does not mean the stuff can't/won't fall back "down". In this case the stuff flung "up" happens to have the necessary properties to trigger star formation further away, which is mostly an incoming shock wave and an preexisting cloud of "cold" stuff. The stuff the BH is throwing in its shock wave is not going to be "cold". So to facilitate star formation the shock wave has to be less hot / less dense than and maybe slower than a larger BH hole would produce (which would more typically shred the cold cloud to tatters instead of causing it to collapse in on itself precipitating a star)
- pdonis 5y ago
  > the star itself or its remains will still likely end up inside the black hole Not necessarily. Black holes don't have any more tendency to "suck things in" from a distance than any other object with the same mass.
  - tejtm 5y ago
    space is pretty big, but I would bet eternity wins this one.
    - jonshariat 5y ago
      As a layperson, I always wondered this about gravity. Does it attract over infinite distance or does it have a range?
      - karmakaze 5y ago
        Thinking in continuous terms, it would be infinite and inversely proportional to distance squared. But thinking in terms of a distortion in space-time and also considering that it may be quantized, perhaps there is some limit. Also for points that are separating faster than the speed of light due to inflation gravity couldn't alter that space.
        pdonis 5y ago
        > for points that are separating faster than the speed of light due to inflation gravity couldn't alter that space. This is not correct. The effects of inflation on spacetime geometry are a form of "gravity" as far as GR is concerned. They're just not a form of "gravity" that you could ever get out of the Newtonian approximation.
        karmakaze 5y ago
        I don't see how this could work. Say there's a significant increase in mass at a point in space A. And there's another point B that's where the distance A-B is separating faster than the speed of light. How could any changes in mass at point A alter the spacetime/gravity at point B? Are we presuming a means of propagating changes faster than light via graviton?
jvanderbot 5y ago
You can orbit a black hole like any other object, and most things do, for a long, long time. Hell, the whole milky way is basically orbiting a black hole (and a lot of other mass near the center).
- fennecfoxen 5y ago
  And orbiting a black hole is just like orbiting any other object, except the surface is much closer to the center of mass.
- ben_w 5y ago
  And some of the stars close to the Milky Way’s have completed entire orbits on camera: https://www.eso.org/public/videos/eso1825e/ https://www.eso.org/public/videos/eso1825e/
- thehappypm 5y ago
  I recently learned about delta-V as a concept. Flying directly into the sun, for example, is basically not possible for a spacecraft with today’s technology, without dozens of gravity boosts. You need to basically undo the speed of your initial orbit, which for something in orbit around a star is huge! A black hole would be even more difficult and require more Delta-V to fly into, if you’re in any sort of orbit. So you should definitely expect tons of stuff in orbit around them!
- acomjean 5y ago
  So all matter is doomed to get sucked into one of these things eventually?
  - jvanderbot 5y ago
    AFAIK, all matter is doomed to be torn apart by the expansion of the universe.
  - isomel 5y ago
    No. For the same reason all matter in the solar system is not doomed to get sucked into the sun. A black hole is just a very dense objet things can fall into if they have the right trajectory. But more often than not, the trajectory will be an hyperbola or a parabola around it, and the matter don't reach the event horizon.
pdonis 5y ago
> I thought a pretty big defining factor of black holes was that nothing (not even light!) ever escaped it? Nothing ever escapes from inside the hole's horizon. But there can still be a lot of interesting things happening outside the hole's horizon as matter either falls in, or orbits the hole, or some combination of the two; and we can certainly observe things happening outside the hole. That has been known for decades.
- alex_young 5y ago
  > Nothing ever escapes from inside the hole's horizon. Well, kind of. Hawking radiation [0] causes black holes to eventually evaporate, although no actual information from inside the horizon escapes. [0] https://en.m.wikipedia.org/wiki/Hawking_radiation https://en.m.wikipedia.org/wiki/Hawking_radiation
  - pdonis 5y ago
    I wasn't including Hawking radiation because, however likely it is considered, it's still not a confirmed prediction, and the theoretical basis for it is not rigorous (since we don't have a consistent theory of quantum gravity to back it up, just various heuristic arguments). (Also, even if it does exist, it is negligible by many, many orders of magnitude in the scenarios under discussion here.) Also, if Hawking radiation does turn out to be confirmed, it might end up that the radiation does carry information from inside the hole. The quantum effects that are involved in Hawking radiation, at least as we currently understand them, violate the conditions that ground the "no information can escape from a black hole" theorems in classical GR.
colechristensen 5y ago
No it’s not a big deal, they just mean that far away from the black hole its effect stirs the pot a bit in a way that triggers star formation. Interesting to observe but also a pretty obvious consequence of a black hole being around.

by belval 5y ago

uoaei 5y ago

It is definitely an unusual observation, but I don't think it's really that big of a deal. A strong gravitational field would pull matter closer together, possibly kick-starting the fusion process if the energy density gets high enough in a certain region. If you asked an astrophysicist what would happen to a massive dust and gas cloud near a black hole, star formation would be 2 or 3 on the list that they rattle off. > But the gentler outflow of gas from the black hole in Henize 2-10 is compressed just enough to facilitate star formation. It's a Goldilocks thing. Black hole is strong enough to have a significant gravity, but weak enough that the shell of hot dense matter it harbors doesn't completely obliterate everything that falls toward it.

kadoban 5y ago

This is not evidence that anything has escaped the event horizon of a black hole. That _would_ be huge news (also pretty ~impossible, but still). This is just the region _near_ a black hole doing some star formation. Which is cool, but also :shrug:.

davesque 5y ago

I don't think this finding challenges any of those assumptions. I think the explanation was that the relativistic jet for smaller blackholes located at galaxy centers is moving slow enough that the compressive effects of the jet are not overcome by the speed. The compression therefore helps with star formation since the jet isn't moving fast enough to disrupt that process.

tejtm 5y ago

Might help to think of it as more of a reprieve. In that the star itself or its remains will still likely end up inside the black holes Schwarzschild radius never to be seen again except as Hawking radiation till the BH evaporates. That the environment directly outside a BH is energetic enough fling some stuff "up" does not mean the stuff can't/won't fall back "down". In this case the stuff flung "up" happens to have the necessary properties to trigger star formation further away, which is mostly an incoming shock wave and an preexisting cloud of "cold" stuff. The stuff the BH is throwing in its shock wave is not going to be "cold". So to facilitate star formation the shock wave has to be less hot / less dense than and maybe slower than a larger BH hole would produce (which would more typically shred the cold cloud to tatters instead of causing it to collapse in on itself precipitating a star)

pdonis 5y ago
> the star itself or its remains will still likely end up inside the black hole Not necessarily. Black holes don't have any more tendency to "suck things in" from a distance than any other object with the same mass.
- tejtm 5y ago
  space is pretty big, but I would bet eternity wins this one.
  - jonshariat 5y ago
    As a layperson, I always wondered this about gravity. Does it attract over infinite distance or does it have a range?
    - karmakaze 5y ago
      Thinking in continuous terms, it would be infinite and inversely proportional to distance squared. But thinking in terms of a distortion in space-time and also considering that it may be quantized, perhaps there is some limit. Also for points that are separating faster than the speed of light due to inflation gravity couldn't alter that space.
      - pdonis 5y ago
        > for points that are separating faster than the speed of light due to inflation gravity couldn't alter that space. This is not correct. The effects of inflation on spacetime geometry are a form of "gravity" as far as GR is concerned. They're just not a form of "gravity" that you could ever get out of the Newtonian approximation.
        karmakaze 5y ago
        I don't see how this could work. Say there's a significant increase in mass at a point in space A. And there's another point B that's where the distance A-B is separating faster than the speed of light. How could any changes in mass at point A alter the spacetime/gravity at point B? Are we presuming a means of propagating changes faster than light via graviton?

jvanderbot 5y ago

You can orbit a black hole like any other object, and most things do, for a long, long time. Hell, the whole milky way is basically orbiting a black hole (and a lot of other mass near the center).

fennecfoxen 5y ago
And orbiting a black hole is just like orbiting any other object, except the surface is much closer to the center of mass.
ben_w 5y ago
And some of the stars close to the Milky Way’s have completed entire orbits on camera: https://www.eso.org/public/videos/eso1825e/ https://www.eso.org/public/videos/eso1825e/
thehappypm 5y ago
I recently learned about delta-V as a concept. Flying directly into the sun, for example, is basically not possible for a spacecraft with today’s technology, without dozens of gravity boosts. You need to basically undo the speed of your initial orbit, which for something in orbit around a star is huge! A black hole would be even more difficult and require more Delta-V to fly into, if you’re in any sort of orbit. So you should definitely expect tons of stuff in orbit around them!
acomjean 5y ago
So all matter is doomed to get sucked into one of these things eventually?
- jvanderbot 5y ago
  AFAIK, all matter is doomed to be torn apart by the expansion of the universe.
- isomel 5y ago
  No. For the same reason all matter in the solar system is not doomed to get sucked into the sun. A black hole is just a very dense objet things can fall into if they have the right trajectory. But more often than not, the trajectory will be an hyperbola or a parabola around it, and the matter don't reach the event horizon.

pdonis 5y ago

> I thought a pretty big defining factor of black holes was that nothing (not even light!) ever escaped it? Nothing ever escapes from inside the hole's horizon. But there can still be a lot of interesting things happening outside the hole's horizon as matter either falls in, or orbits the hole, or some combination of the two; and we can certainly observe things happening outside the hole. That has been known for decades.

alex_young 5y ago
> Nothing ever escapes from inside the hole's horizon. Well, kind of. Hawking radiation [0] causes black holes to eventually evaporate, although no actual information from inside the horizon escapes. [0] https://en.m.wikipedia.org/wiki/Hawking_radiation https://en.m.wikipedia.org/wiki/Hawking_radiation
- pdonis 5y ago
  I wasn't including Hawking radiation because, however likely it is considered, it's still not a confirmed prediction, and the theoretical basis for it is not rigorous (since we don't have a consistent theory of quantum gravity to back it up, just various heuristic arguments). (Also, even if it does exist, it is negligible by many, many orders of magnitude in the scenarios under discussion here.) Also, if Hawking radiation does turn out to be confirmed, it might end up that the radiation does carry information from inside the hole. The quantum effects that are involved in Hawking radiation, at least as we currently understand them, violate the conditions that ground the "no information can escape from a black hole" theorems in classical GR.

colechristensen 5y ago

No it’s not a big deal, they just mean that far away from the black hole its effect stirs the pot a bit in a way that triggers star formation. Interesting to observe but also a pretty obvious consequence of a black hole being around.