S-Massive Black Holes Eat Less Than Thought

[cacoseraph]

Why Super Massive Black Holes Consume Less Material Than Expected

Aug. 29, 2013 — Using NASA's super-sensitive Chandra X-ray space telescope, a team of astronomers led by Q. Daniel Wang at the University of Massachusetts Amherst has solved a long-standing mystery about why most super massive black holes (SMBH) at the centers of galaxies have such a low accretion rate -- that is, they swallow very little of the cosmic gases available and instead act as if they are on a severe diet.

http://www.scienceda...30829145131.htm

The article didn't baby talk exactly what the mechanism that prevents the SMBH from eating more. I wonder if it is something like the radiant pressure that helps to keep stars from collapsing in on themselves?

[spacecowboy342]

Why Super Massive Black Holes Consume Less Material Than Expected

http://www.scienceda...30829145131.htm

The article didn't baby talk exactly what the mechanism that prevents the SMBH from eating more. I wonder if it is something like the radiant pressure that helps to keep stars from collapsing in on themselves?

Sounds to me like it is the velocity of the material itself keeping it in orbit around the BH and not being devoured. I wonder if time dilational effects around the singularity affect observation or if this is taken into account(surely it must be)

[Frank Merton]

Well anything that big needs to go on a diet.

[cacoseraph]

Sounds to me like it is the velocity of the material itself keeping it in orbit around the BH and not being devoured. I wonder if time dilational effects around the singularity affect observation or if this is taken into account(surely it must be)

I thought maybe something like that, but it seems that the article made more of a point that it is the heat of the gas rather than velocity preventing crossing the event horizon. That's what made me think maybe it was radiant pressure related.

I could totally see the velocity thing, though... like a gravity sling for fast moving particles that are not directly pointed inside the event horizon. Which leads to another question. Since the mass (and maybe spin? little vague on the physics of it) of a blackhole determines its gravity well and event horizon and I believe gravity slinging transfers the velocity from the more massive object to the smaller object, does that mean that process would diminish the black hole somehow?

[spacecowboy342]

I thought maybe something like that, but it seems that the article made more of a point that it is the heat of the gas rather than velocity preventing crossing the event horizon. That's what made me think maybe it was radiant pressure related.

I could totally see the velocity thing, though... like a gravity sling for fast moving particles that are not directly pointed inside the event horizon. Which leads to another question. Since the mass (and maybe spin? little vague on the physics of it) of a blackhole determines its gravity well and event horizon and I believe gravity slinging transfers the velocity from the more massive object to the smaller object, does that mean that process would diminish the black hole somehow?

Is heat of a gas not a measure of the kinetic energy of the molecules of that gas? Kinetic energy would seem to me to equate to velocity, but I'm not a physicist. I don't think the process you describe would diminish the BH(except in the case of Hawking radiation) other than perhaps to affect it's spin somewhat,but I am guessing here

[cacoseraph]

Is heat of a gas not a measure of the kinetic energy of the molecules of that gas? Kinetic energy would seem to me to equate to velocity, but I'm not a physicist. I don't think the process you describe would diminish the BH(except in the case of Hawking radiation) other than perhaps to affect it's spin somewhat,but I am guessing here

This is past my personal knowledge. I know that temperature is a measure of movement of molecules or something like that. So, in a sense, it seems that you would be correct.

The diminish question could be summed up kind of like, our universe seems to never give something for nothing. If the particles being directed away do gain velocity it seems like their gain requires a loss somewhere else. Since it seems like in a two actor play when one actor gains velocity the other actor must lose... something. Of course, limiting the play to two actors could easily be wrong and such a gross over simplification that the only appropriate response is laughter.

[sepulchrave]

In this circumstances, temperature is a measure of the incoherent, or randomly directed kinetic energy of an collection of particles.

I am not an expert in this field, but I think the mechanism at play here is that as some particles fall towards the black hole (i.e. take on a coherent direction) they greatly increase the scattering of nearby particles, directing them away from the black hole.

Very simply speaking, I would say it is analogous to the case of ``warm air rising''.