Physics behind black hole jets?

Hi all...

saw a show last night on extreme energy astronomy...and even though it was
narrated by "captain kirk"...it was a generally good show about uv, x ray,
gamma etc astronomy...

Anyway...at one point they had this nice animation of a black hole swallowing
gas from an expanding companion star...

so you had this streamer of gas from the star feeding the outer edge of an
accrection disk....then the gas spiraled along the disc until it disappeared
into the black hole...

And then you also had these VERY energetic jets streaming from/near the black
hole and i get the impression that the jets are supposed to be perpendicular to
the disk....

So two questions:

First, why a disk? Now this one doesnt bother me too much as I have some ideas
anyway and at least it doesnt seem counterintuitive....

The second and more bothersome question to me is WHAT is the mechanism for the
EJECTING jets?

take care

Blll

IIRC, it's something to do with magnetic fields, poles, and charged gas.

"BllFs6" wrote in message
...
Hi all...

saw a show last night on extreme energy astronomy...and even though it was
narrated by "captain kirk"...it was a generally good show about uv, x ray,
gamma etc astronomy...

Anyway...at one point they had this nice animation of a black hole
swallowing
gas from an expanding companion star...

so you had this streamer of gas from the star feeding the outer edge of an
accrection disk....then the gas spiraled along the disc until it
disappeared
into the black hole...

And then you also had these VERY energetic jets streaming from/near the
black
hole and i get the impression that the jets are supposed to be
perpendicular to
the disk....

So two questions:

First, why a disk? Now this one doesnt bother me too much as I have some
ideas
anyway and at least it doesnt seem counterintuitive....

The second and more bothersome question to me is WHAT is the mechanism for
the
EJECTING jets?

take care

Blll









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BllFs6 wrote in message
...
Hi all...

saw a show last night on extreme energy astronomy...and even though it was
narrated by "captain kirk"...it was a generally good show about uv, x ray,
gamma etc astronomy...

Anyway...at one point they had this nice animation of a black hole
swallowing gas from an expanding companion star...

so you had this streamer of gas from the star feeding the outer edge of an
accrection disk....then the gas spiraled along the disc until it
disappeared into the black hole...

And then you also had these VERY energetic jets streaming from/near the
black hole and i get the impression that the jets are supposed to be
perpendicular to the disk....

So two questions:

First, why a disk? Now this one doesnt bother me too much as I have some
ideas anyway and at least it doesnt seem counterintuitive....

Accretion disks form around any dense gravitating body. They form around
white dwarfs (which we have directly observed). They form around neutron
stars (which we have directly observed). They would form around a black
hole (which -- by definition -- we cannot directly observe). The central
objects in these cases are all no larger than about the size of the Earth
(white dwarf is largest) and contain masses on the order of the Sun (about
0.1 solar mass and up). The accretion disks typically have sizes that are on
the order of Solar system planetary orbits. So one cannot always tell from
just looking at a disk what type of central mass is inside, causing the
disk.

An accretion disk forms because incoming gas that is even the slightest bit
off-center will tend to go into orbit around the star or hole. But because
gas is not a single body, the dynamics of the interactions of all the
multitudes of gas atoms and dust particles and chunks of rock that enter
into orbit will tend to flatten the orbits into a disk, around the common
center of angular momentum. Similar gravitational processes are thought to
flatten forming disk galaxies and stellar planetary systems.

As the gas particles orbit, collisional 'friction' will tend to cause orbits
of the material in the disk to slowly decay and spiral into the central
mass. The easiest way to visualize this, is to note that if two particles
collide, the one that is closer in will have an orbit that has a higher
speed (individual orbits aren't purely circular). After the collision, the
'inner' particle will have lost energy -- and will therefore move into a
closer orbit. Repeat untold times.

The second and more bothersome question to me is WHAT is the mechanism for
the EJECTING jets?

There is no postulated physical cause for black holes to 'eject' jets that
is generally accepted. The 'black hole is the energy source for jets' is
postulated primarily because cosmologists cannot find any other energy
source sufficient for their theories to match observation. So -- even
though there is no known mechanism -- the 'black hole' explanation is quite
common.

There are other known sources of jets (i.e. magnetic fields). But none of
these can drive jets of the magnitude calculated by the cosmologists of many
sources. Of course, this could simply mean that some prior distance
calculation was in error, and the object is closer than the cosmologists
think it is.

--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}

"greywolf42" wrote in message ...
BllFs6 wrote in message
...
Hi all...

saw a show last night on extreme energy astronomy...and even though it was
narrated by "captain kirk"...it was a generally good show about uv, x ray,
gamma etc astronomy...

Anyway...at one point they had this nice animation of a black hole
swallowing gas from an expanding companion star...

so you had this streamer of gas from the star feeding the outer edge of an
accrection disk....then the gas spiraled along the disc until it
disappeared into the black hole...

And then you also had these VERY energetic jets streaming from/near the
black hole and i get the impression that the jets are supposed to be
perpendicular to the disk....

So two questions:

First, why a disk? Now this one doesnt bother me too much as I have some
ideas anyway and at least it doesnt seem counterintuitive....

Accretion disks form around any dense gravitating body. They form around
white dwarfs (which we have directly observed). They form around neutron
stars (which we have directly observed). They would form around a black
hole (which -- by definition -- we cannot directly observe). The central
objects in these cases are all no larger than about the size of the Earth
(white dwarf is largest) and contain masses on the order of the Sun (about
0.1 solar mass and up). The accretion disks typically have sizes that are on
the order of Solar system planetary orbits. So one cannot always tell from
just looking at a disk what type of central mass is inside, causing the
disk.

An accretion disk forms because incoming gas that is even the slightest bit
off-center will tend to go into orbit around the star or hole. But because
gas is not a single body, the dynamics of the interactions of all the
multitudes of gas atoms and dust particles and chunks of rock that enter
into orbit will tend to flatten the orbits into a disk, around the common
center of angular momentum. Similar gravitational processes are thought to
flatten forming disk galaxies and stellar planetary systems.

As the gas particles orbit, collisional 'friction' will tend to cause orbits
of the material in the disk to slowly decay and spiral into the central
mass. The easiest way to visualize this, is to note that if two particles
collide, the one that is closer in will have an orbit that has a higher
speed (individual orbits aren't purely circular). After the collision, the
'inner' particle will have lost energy -- and will therefore move into a
closer orbit. Repeat untold times.

The second and more bothersome question to me is WHAT is the mechanism for
the EJECTING jets?

There is no postulated physical cause for black holes to 'eject' jets that
is generally accepted. The 'black hole is the energy source for jets' is
postulated primarily because cosmologists cannot find any other energy
source sufficient for their theories to match observation. So -- even
though there is no known mechanism -- the 'black hole' explanation is quite
common.

There are other known sources of jets (i.e. magnetic fields). But none of
these can drive jets of the magnitude calculated by the cosmologists of many
sources. Of course, this could simply mean that some prior distance
calculation was in error, and the object is closer than the cosmologists
think it is.

And these jets (gas bodies) are observed to be travelling at 99.8%c .
SR says therefore they should appear very shortened (almost
disappeared), but there they are thousands of light years long!
(Isn't SR funny?)

Jim G

"greywolf42" bravely wrote to "All" (30 Jan 04 10:28:02)
--- on the heady topic of " Physics behind black hole jets?"

gr From: "greywolf42"

gr BllFs6 wrote in message
gr ...
Hi all...

saw a show last night on extreme energy astronomy...and even though it was
narrated by "captain kirk"...it was a generally good show about uv, x ray,
gamma etc astronomy...

Anyway...at one point they had this nice animation of a black hole
swallowing gas from an expanding companion star...

so you had this streamer of gas from the star feeding the outer edge of an
accrection disk....then the gas spiraled along the disc until it
disappeared into the black hole...

And then you also had these VERY energetic jets streaming from/near the
black hole and i get the impression that the jets are supposed to be
perpendicular to the disk....

So two questions:

First, why a disk? Now this one doesnt bother me too much as I have some
ideas anyway and at least it doesnt seem counterintuitive....

gr Accretion disks form around any dense gravitating body. They form
gr around white dwarfs (which we have directly observed). They form
gr around neutron stars (which we have directly observed). They would
gr form around a black hole (which -- by definition -- we cannot directly
gr observe). The central objects in these cases are all no larger than
gr about the size of the Earth (white dwarf is largest) and contain masses
gr on the order of the Sun (about 0.1 solar mass and up). The accretion
gr disks typically have sizes that are on the order of Solar system
gr planetary orbits. So one cannot always tell from just looking at a
gr disk what type of central mass is inside, causing the disk.

gr An accretion disk forms because incoming gas that is even the
gr slightest bit off-center will tend to go into orbit around the star or
gr hole. But because gas is not a single body, the dynamics of the
gr interactions of all the multitudes of gas atoms and dust particles and
gr chunks of rock that enter into orbit will tend to flatten the orbits
gr into a disk, around the common center of angular momentum. Similar
gr gravitational processes are thought to flatten forming disk galaxies
gr and stellar planetary systems.
gr As the gas particles orbit, collisional 'friction' will tend to cause
gr orbits of the material in the disk to slowly decay and spiral into the
gr central mass. The easiest way to visualize this, is to note that if
gr two particles collide, the one that is closer in will have an orbit
gr that has a higher speed (individual orbits aren't purely circular).
gr After the collision, the 'inner' particle will have lost energy -- and
gr will therefore move into a closer orbit. Repeat untold times.

I think there is a possibility because of the very powerful tidal
forces in really massive objects such as neutron stars and black holes
that they don't have disks but rather have bands or arcs on either
side of the object. The openings inbetween would be swept free of
material by extremely powerful particle winds thus the spiralling disk
idea doesn't feel right to me. Such exotic massive objects are not
likely to be explained with simple mechanisms but may even require new
science to do so adequately.

.... And on the 8th day God said, "Murphy, you're in charge."

In message , Jim
Greenfield writes
"greywolf42" wrote in message
...

There are other known sources of jets (i.e. magnetic fields). But none of
these can drive jets of the magnitude calculated by the cosmologists of many
sources. Of course, this could simply mean that some prior distance
calculation was in error, and the object is closer than the cosmologists
think it is.

And these jets (gas bodies) are observed to be travelling at 99.8%c .
SR says therefore they should appear very shortened (almost
disappeared), but there they are thousands of light years long!
(Isn't SR funny?)

How do you work that out? If something ejects matter moving at the speed
of light (or 99.8% of it) for a thousand years you're going to get a jet
a thousand light years long.
--
Save the Hubble Space Telescope!
Remove spam and invalid from address to reply.

greywolf42 wrote:

BllFs6 wrote in message
...
Hi all...

saw a show last night on extreme energy astronomy...and even though it was
narrated by "captain kirk"...it was a generally good show about uv, x ray,
gamma etc astronomy...

Anyway...at one point they had this nice animation of a black hole
swallowing gas from an expanding companion star...

so you had this streamer of gas from the star feeding the outer edge of an
accrection disk....then the gas spiraled along the disc until it
disappeared into the black hole...

And then you also had these VERY energetic jets streaming from/near the
black hole and i get the impression that the jets are supposed to be
perpendicular to the disk....

So two questions:

First, why a disk? Now this one doesnt bother me too much as I have some
ideas anyway and at least it doesnt seem counterintuitive....

Accretion disks form around any dense gravitating body. They form around
white dwarfs (which we have directly observed). They form around neutron
stars (which we have directly observed). They would form around a black
hole (which -- by definition -- we cannot directly observe).

Why not?
As long as the disk is *outside* of the (event horizon of the) black hole,
radiation from the disk can escape.

db

db wrote in message ...
greywolf42 wrote:

BllFs6 wrote in message
...
Hi all...

saw a show last night on extreme energy astronomy...and even though it
was
narrated by "captain kirk"...it was a generally good show about uv, x
ray,
gamma etc astronomy...

Anyway...at one point they had this nice animation of a black hole
swallowing gas from an expanding companion star...

so you had this streamer of gas from the star feeding the outer edge
of an
accrection disk....then the gas spiraled along the disc until it
disappeared into the black hole...

And then you also had these VERY energetic jets streaming from/near
the
black hole and i get the impression that the jets are supposed to be
perpendicular to the disk....

So two questions:

First, why a disk? Now this one doesnt bother me too much as I have
some
ideas anyway and at least it doesnt seem counterintuitive....

Accretion disks form around any dense gravitating body. They form
around
white dwarfs (which we have directly observed). They form around
neutron
stars (which we have directly observed). They would form around a black
hole (which -- by definition -- we cannot directly observe).

Why not?
As long as the disk is *outside* of the (event horizon of the) black hole,
radiation from the disk can escape.

It is the black hole is itself not observable. The disk is observable.

We have direct images of white dwarfs and (at least one) neutron stars.

Black holes theoretically can only be inferred.

--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}

Jonathan Silverlight wrote in message ...
In message , Jim
Greenfield writes
"greywolf42" wrote in message
...

There are other known sources of jets (i.e. magnetic fields). But none of
these can drive jets of the magnitude calculated by the cosmologists of many
sources. Of course, this could simply mean that some prior distance
calculation was in error, and the object is closer than the cosmologists
think it is.

And these jets (gas bodies) are observed to be travelling at 99.8%c .
SR says therefore they should appear very shortened (almost
disappeared), but there they are thousands of light years long!
(Isn't SR funny?)

How do you work that out? If something ejects matter moving at the speed
of light (or 99.8% of it) for a thousand years you're going to get a jet
a thousand light years long.

The '1000s of light years' isn't a "time" though, when discussing the
length of the jet- it is a length "measure". The body of gas is moving
as one entity (although being added to at source), and therefore,
since it is moving at such high speed, should appear much shortened if
SR is correct. If it appears this large at that velocity, it must be
REALLY long!
(Sorry- I couldn't resist this opportunity for a shot at SR. I'd
better get out of this thread, before my off topic earns me a severe
reprimand/abuse/naughty words)

Jim G

In message , Jim
Greenfield writes
Jonathan Silverlight
wrote in message ...

How do you work that out? If something ejects matter moving at the speed
of light (or 99.8% of it) for a thousand years you're going to get a jet
a thousand light years long.

The '1000s of light years' isn't a "time" though, when discussing the
length of the jet- it is a length "measure". The body of gas is moving
as one entity (although being added to at source), and therefore,
since it is moving at such high speed, should appear much shortened if
SR is correct. If it appears this large at that velocity, it must be
REALLY long!

But it isn't a single entity, it's a stream of individual particles,
each of which is subject to Lorentz contraction. By your reasoning, a
beam of light would never get anywhere because it would be reduced to
zero length.
--
Save the Hubble Space Telescope!
Remove spam and invalid from address to reply.