Re: How can we 'see' a blackhole?

"Chris L Peterson" <clp@xxxxxxxxxxxxxxxxxx> wrote in message
news:m020t29t60k2aiql7retiaond6ao044497@xxxxxxxxxx
On Mon, 12 Feb 2007 01:07:17 -0500, "Greg Neill"
<gneillREM@xxxxxxxxxxxxxx> wrote:

I need to find some figures on the expected infall time
for matter in an accretion disk (i.e. persistence time
for the disks of a non-accreting black hole). I'll
keep browsing.

Just for fun, I did a back of the envelope calculation. Assuming the
black hole is traveling 20 km/s and sweeps up all the interstellar
matter (1e-21 kg/m^3) across a 10 km cross section, and that it
completely converts the mass to energy, the output will be 1.4e8 J, or
the equivalent of 34 kg TNT per second. In practice, the energy would be
less. I doubt we could detect such an energy source at any appreciable
distance. You'd need a black hole that already had one of these stable
accretion disks before it got launched, and then you'd need it to pump a
lot of its own energy into the disk, but without driving material out of
the disk, which can only collect new material at about 1 microgram per
second. Sounds unlikely to me.

If the disk is in equilibrium it will be a permanent
structure without requiring further accretion. The
radiant energy comes entirely from angular momentum
transfer from the BH itself.

In order to see if such a disk could form around an
initially "naked" BH merely by gathering up interstellar
matter (although presumably it should have been able to
take along quite a bit of stuff from whence the BH was
first created and ejected), we need figures on the decay
rate of the disk vs accretion rate. It's these decay
rate figures that we need to find.


.

Relevant Pages

  • The True Colour of Black Hole Disks (Forwarded)
    ... Max Planck Institute for Radio Astronomy, ... The True Colour of Black Hole Disks ... AGN is a massive accretion disk which is believed to be the source of most ... thought to be sucked into the hole from a surrounding "accretion disk". ...
    (sci.space.news)
  • Dark Matter Discovered in Accretion Disks (Forwarded)
    ... National Optical Astronomy Observatory ... Concepts of Disk Structure and Luminosity ... Observations of the interacting binary star using telescopes at Kitt Peak ... "The much larger size of the infrared-emitting portion of the accretion disk ...
    (sci.space.news)
  • Re: There are no black holes
    ... on the disk. ... That upon approaching the event horizon, dark energy arises that warps ... Mass and light heading straight toward a black hole would not enter the ... gravity is near annihilated by dark energies. ...
    (sci.astro)
  • Re: How can we see a blackhole?
    ... for matter in an accretion disk (i.e. persistence time ... for the disks of a non-accreting black hole). ... In practice, the energy would be ...
    (sci.astro.amateur)
  • Re: How can we see a blackhole?
    ... for matter in an accretion disk (i.e. persistence time ... for the disks of a non-accreting black hole). ... In practice, the energy would be ...
    (sci.astro.amateur)