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?
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.
Well, kind of. Hawking radiation [0] causes black holes to eventually evaporate, although no actual information from inside the horizon escapes.
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.
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!
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.
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)
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.
So thinking of gravity as a Newtonian "attraction over infinite distance" doesn't really work in GR, but neither does thinking of it as a "force" with a finite range. It works differently from either of those.
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.
At some range, any field will decrease to below thermal noise of medium.
Is there some mass-distance(-velocity?) function that defines the alternative fates? Where below some threshold, things are fated to merge and beyond which ...not so much.
I am pretty confident all the mass on the earth would be expected to end up together, and would be comfortable imagining that theoretical planets on opposite sides of the observable universe may never merge but what is the transition point? the solar system? the milky way? the local group?
This is just the region _near_ a black hole doing some star formation. Which is cool, but also :shrug:.
> 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.