Slashdot Mirror
Black Holes May Not Grow Beyond Certain Limit
xyz writes "Do black holes increase in size indefinitely? According to an analysis by astronomers at Yale and the European Southern Observatory, the maximum size a black hole may reach is only few tens of billion of solar masses. The limit was calculated using an analysis of what may happen to the gas surrounding a black hole which has reached few tens of billions of solar masses. It is thought that black holes of such size heat the surrounding gas to a temperature where the radiation pressure begins blowing outer layers into space."
I'm not an astrophysicist either, but as far as I can tell nothing about this hypothesis contradicts the idea that once matter crosses the event horizon it doesn't come out again, except as radiation. They aren't saying that the black hole begins "ejecting" gas, just that at that mass it gives off enough radiation to prevent any more gas from falling in.
I'm not sure I buy that as setting an upper limit on the size of a black hole. It just means the rate of growth would slow, and potentially reach equilibrium with regards to the surrounding gas. If something denser, like a star were to fall in, I doubt that the radiation pressure would push it away.
But who knows. I don't.
If fate makes you a motorcycle, you become a motorcycle.
Side note: makes much more sense then the big bang theory, which reeks of creationism.
So, instead of using rational thought and evidence to decide what theory is correct, you're going to use your "gut" feeling to make the determination? Sounds a little like what the relgionists, that you're so quick to deride, like to do.
Mad Software: Rantings on Developing So
Don't feel bad, the physics is way beyond the string theorists, so they just make up the math as they go along.
All I could think of was that I really wish they called micro black holes that exist for minute fractions of a second something other than "black holes."
Microscopic singularities. Of course, the press wouldn't eat that up; newspapers don't exist to educate the public, they exist to generate revenue.
Free Martian Whores!
OK, read again. You still sound foolish.
Doesn't sound like an afterthought. Sounds like the whole point.
Mad Software: Rantings on Developing So
I came here to post almost the exact same thing. The story is about a limit to the size of black holes with respect to the ways the universe is expected to have developed. This is not a hard limit on the size but more of an equilibrium thing as the parent mentioned.
Think about this thought experiment:
One finds a black hole and shoots energy into it in the form of light in discrete sized packets or quanta. If the packets are put in faster than the natural blackbody radiation of the black whole releases energy through Hawking radiation, it will grow in size. Since the black body temperature of the hole decreases as it gets larger, it can grow in this way indefinitely. The larger it is, the softer it pushes outwards (w.r.t HR)...
The story is only really talking about matter/gas clouds, EM energy is an entirely different beast.
I am a viral sig. Please help me spread.
Lets see if we can clear some of this up for everyone...
When you have a black hole sucking in matter, that matter will start to get denser as it gets closer to the black hole. The larger the black hole the farther its gravitational influence and the more matter it can attract. As the matter falls in and gets denser its rotational momentum causes it to orbit. As this happens it starts to get quite close together and due to friction begins to heat up. Eventually it gets really really hot and expands as well as emitting high energy radiation. Once this reaches a critical point it overpowers the gravity of the black hole attracting said matter and starts blowing it back out.
Eventually this wind will be dissapated and will be inconsequencial on the scale of 100s of light years. Since galaxies are tens of thousands of LY across the intergalactic medium is not affected by this.
Again, this is not due to anything being emitted directly from the black hole, only the superheated matter falling into it.
The energy to blow away the dust and gas from the black hole comes from infalling dust and gas. In the absence of infalling dust and gas the black hole doesn't emit any energy at all. So once it reaches this limit, and clears out the nearby vicinity of the hole, what keeps its neighborhood clear? It's no longer taking in matter, the radiation pressure drops, and the expelled matter eventually returns to start te growth again, no?
This all sounds like the T-Tauri stage in stellar evolution... except that the star continues to radiate, and the black hole doesn't.
It is questionable if it is acceptable to do so if they are end-term on a horrific disease, due to the chance of recovery.
The girl in India thought that she was at the end-term of humanity with zero chance of recovery. According to what she knew, even your definition makes her suicide acceptable.