How can black holes "expell" jets of gas?

I will admit to being a little confused after reading the alt.astronomy
FAQ, and note that Google groups simply lists sci.astronomy as "an
archive" to which I can not pose questions. I have what I think is a
simple question.

In the July 2006 issue of Sky & Telescope, there's an article about how
many galaxies are at one (or more) point(s) in their careers quasars.
This is because they have large black holes at their centers, which
accrete large volumes of gas, stars, and even other galaxies. However,
in this process, they are described as expelling "jets" of gas, some of
which are accelerated close to "the speed of light."

My understanding of black holes is that of a lay person, rather than
mathematical. This seems to contradict the notion of a black hole. One
quote from the article is that as gas approaches the black hole, it
releases energy, which is flung away from the black hole. I'm not sure
how this is possible. After gas (or indeed matter in general) has begun
its "fall" into the black hole, I thought it was inevitable that it
would wind up there?

If I've posted here in error, I apologize.

Alex

wrote in message ups.com...
I will admit to being a little confused after reading the alt.astronomy
FAQ, and note that Google groups simply lists sci.astronomy as "an
archive" to which I can not pose questions. I have what I think is a
simple question.

In the July 2006 issue of Sky & Telescope, there's an article about how
many galaxies are at one (or more) point(s) in their careers quasars.
This is because they have large black holes at their centers, which
accrete large volumes of gas, stars, and even other galaxies. However,
in this process, they are described as expelling "jets" of gas, some of
which are accelerated close to "the speed of light."

My understanding of black holes is that of a lay person, rather than
mathematical. This seems to contradict the notion of a black hole. One
quote from the article is that as gas approaches the black hole, it
releases energy, which is flung away from the black hole. I'm not sure
how this is possible. After gas (or indeed matter in general) has begun
its "fall" into the black hole, I thought it was inevitable that it
would wind up there?

If I've posted here in error, I apologize.

The material comprising the jets was never below
the event horizon of the black hole, it is material
that is forced away from the accretion disk and
"squirted out" along the polar axes. There's
probably some very nifty magnetohydrodynamical
processes involved in entraining the material to
migrate from the equator to the poles and
collimating it into jets.

wrote:
I will admit to being a little confused after reading the alt.astronomy
FAQ,


The alt.astronomy FAQ is a FAKE.

Double-A

On 12 Jun 2006 03:25:05 -0700, "Double-A" wrote:


wrote:
I will admit to being a little confused after reading the alt.astronomy
FAQ,


The alt.astronomy FAQ is a FAKE.

It should have Qs such as:
Is there only one Uranus?

I thought the FAQ was dead on! Has it changed lately?

Saul Levy


On 12 Jun 2006 03:25:05 -0700, "Double-A" wrote:


wrote:
I will admit to being a little confused after reading the alt.astronomy
FAQ,


The alt.astronomy FAQ is a FAKE.

Double-A