Science > Physics > Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate
| Topic: |
Science > Physics |
| User: |
"Chris ORiordan" |
| Date: |
24 Feb 2005 04:16:40 AM |
| Object: |
Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
The conventional explanantion for the superluminal motions observed in
many quasar-type jets is that it is an optical illusion due to the jets
being oriented at a fairly narrow angle to our line of sight.
Some salient question marks over this are:-
As early as 1983, for the relatively few superluminal objects then
known, the jets did not seem to be in general oriented close to the
line of sight;
In 1993 Mackay et al suggested, based on Hubble Telescope observations,
that the jet of the quasar 3C273 was nearly perpendicular, rather than
nearly parallel, to the line of sight (superluminal motion of up to
~9.6c has been observed in the inner jet);
The jet of the galaxy M87 does not seem to have a narrow-enough angle
with our line of sight to explain motion of up to ~6c observed in it.
(I summed up the material at
http://uk.geocities.com/chrisori2000/superjet.htm )
Various technical tricks, such as multiple jet-beams and twisting jets,
or precessing jets, have been proposed, as ways out. Devices which
seem increasingly convoluted in more senses than one, and perhaps as
artificial as that spectrum of tricks proposed to save the "ether" at
the turn of the 19th/20th centuries.
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| User: "Sam Wormley" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" AppearsInadequate |
24 Feb 2005 07:58:13 AM |
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Chris O'Riordan wrote:
The conventional explanantion for the superluminal motions observed in
many quasar-type jets is that it is an optical illusion due to the jets
being oriented at a fairly narrow angle to our line of sight.
http://www.mhhe.com/physsci/astronomy/fix/student/chapter24/24f09.html
http://www.mhhe.com/physsci/astronomy/fix/student/chapter24/24f10.html
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| User: "DavidBowman" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
24 Feb 2005 05:01:35 PM |
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If anyone wants background on this problem, here is a very
good, concise article from astrophysical journal. It includes
fascinating pix of the "superluminal" features over time, too:
http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v520n2/39787/39787.html
=[ d
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| User: "Sam Wormley" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" AppearsInadequate |
24 Feb 2005 06:02:13 PM |
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DavidBowman wrote:
If anyone wants background on this problem, here is a very
good, concise article from astrophysical journal. It includes
fascinating pix of the "superluminal" features over time, too:
http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v520n2/39787/39787.html
Thanks David.
-Sam
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
24 Feb 2005 07:40:54 AM |
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Dear Chris O'Riordan:
"Chris O'Riordan" <coranto@hotmail.com> wrote in message
news:1109240200.587669.118790@z14g2000cwz.googlegroups.com...
The conventional explanantion for the superluminal motions observed in
many quasar-type jets is that it is an optical illusion due to the jets
being oriented at a fairly narrow angle to our line of sight.
....
If the jets are truly superlumenal, how is it that we can see light from
them? Since we *do* see light from them, and their spectra are
"reasonable", the rest is "tricks of geometry". If they were superlumenal,
the light could never leave...
David A. Smith
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| User: "christie.jones" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
24 Feb 2005 09:24:59 AM |
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"N:dlzc D:aol T:com (dlzc)" <N: dlzc1 D:cox T:net@nospam.com> wrote in
message news:kPkTd.81133$Yu.56373@fed1read01...
Dear Chris O'Riordan:
"Chris O'Riordan" <coranto@hotmail.com> wrote in message
news:1109240200.587669.118790@z14g2000cwz.googlegroups.com...
The conventional explanantion for the superluminal motions observed in
many quasar-type jets is that it is an optical illusion due to the jets
being oriented at a fairly narrow angle to our line of sight.
...
If the jets are truly superlumenal, how is it that we can see light from
them? Since we *do* see light from them, and their spectra are
"reasonable", the rest is "tricks of geometry". If they were
superlumenal, the light could never leave...
David A. Smith
Why? If the velocity of light isn't source dependent then what does the
sources velocity have to do with the amount of time it takes for the light
to reach us? BTW I am just asking a question. I'm not saying the source is
going >c.
---
Thomas
"The idea of God is the sole wrong for which I cannot forgive mankind."
--Le Marquis de Sade
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| User: "christie.jones" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
24 Feb 2005 09:29:00 AM |
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"christie.jones" <christie.jones@insightbb.com> wrote in message
news:flmTd.994$r55.269@attbi_s52...
"N:dlzc D:aol T:com (dlzc)" <N: dlzc1 D:cox T:net@nospam.com> wrote in
message news:kPkTd.81133$Yu.56373@fed1read01...
Dear Chris O'Riordan:
"Chris O'Riordan" <coranto@hotmail.com> wrote in message
news:1109240200.587669.118790@z14g2000cwz.googlegroups.com...
The conventional explanantion for the superluminal motions observed in
many quasar-type jets is that it is an optical illusion due to the jets
being oriented at a fairly narrow angle to our line of sight.
...
If the jets are truly superlumenal, how is it that we can see light from
them? Since we *do* see light from them, and their spectra are
"reasonable", the rest is "tricks of geometry". If they were
superlumenal, the light could never leave...
David A. Smith
Why? If the velocity of light isn't source dependent then what does the
sources velocity have to do with the amount of time it takes for the light
to reach us? BTW I am just asking a question. I'm not saying the source
is going >c.
---
Thomas
"The idea of God is the sole wrong for which I cannot forgive mankind."
--Le Marquis de Sade
Nevermind. For some reason I skipped the part about the spectra being
"reasonable". I understand now.
Thomas
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| User: "Jonathan Silverlight" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
24 Feb 2005 02:05:19 PM |
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In message <kPkTd.81133$Yu.56373@fed1read01>, "N:dlzc D:aol T:com
(dlzc)" <N@?.D.invalid> writes
Dear Chris O'Riordan:
"Chris O'Riordan" <coranto@hotmail.com> wrote in message
news:1109240200.587669.118790@z14g2000cwz.googlegroups.com...
The conventional explanantion for the superluminal motions observed in
many quasar-type jets is that it is an optical illusion due to the jets
being oriented at a fairly narrow angle to our line of sight.
...
If the jets are truly superlumenal, how is it that we can see light from
them? Since we *do* see light from them, and their spectra are
"reasonable", the rest is "tricks of geometry". If they were superlumenal,
the light could never leave...
We could see Cerenkov radiation (it's been looked for in searches for
tachyons) but presumably the spectrum from a jet doesn't match what's
expected for Cerenkov radiation, so that's not the answer.
--
Support the DEC Tsunami Appeal http://www.dec.org.uk/.
Remove spam and invalid from address to reply.
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
24 Feb 2005 02:22:59 PM |
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Dear Jonathan Silverlight:
"Jonathan Silverlight" <jsilverlight@spam.merseia.fsnet.co.uk.invalid>
wrote in message news:Y2GSMuv$NjHCFwaX@merseia.fsnet.co.uk...
In message <kPkTd.81133$Yu.56373@fed1read01>, "N:dlzc D:aol T:com (dlzc)"
<N@?.D.invalid> writes
Dear Chris O'Riordan:
"Chris O'Riordan" <coranto@hotmail.com> wrote in message
news:1109240200.587669.118790@z14g2000cwz.googlegroups.com...
The conventional explanantion for the superluminal motions observed in
many quasar-type jets is that it is an optical illusion due to the jets
being oriented at a fairly narrow angle to our line of sight.
...
If the jets are truly superlumenal, how is it that we can see light from
them? Since we *do* see light from them, and their spectra are
"reasonable", the rest is "tricks of geometry". If they were
superlumenal,
the light could never leave...
We could see Cerenkov radiation (it's been looked for in searches for
tachyons) but presumably the spectrum from a jet doesn't match what's
expected for Cerenkov radiation, so that's not the answer.
My point was, if they are moving towards us in any sense, faster than c,
then the particle/body/object will outrun the light. We could *see*
nothing coming towards us. And the faster it is, the closer it would have
to be to "motion at 90 deg to line of sight" to keep from outrunning light
that leaves towards us.
I agree, Cerenkov radiation places limits on ions, and even on sources of
thermally-based light emission (which liberates charges).
David A. Smith
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| User: "Joseph Lazio" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
26 Feb 2005 08:58:21 AM |
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"NDT" == N:dlzc D:aol T:com \(dlzc\) <N> writes:
NDT> My point was, if they are moving towards us in any sense, faster
NDT> than c, then the particle/body/object will outrun the light. We
NDT> could *see* nothing coming towards us. And the faster it is,
NDT> the closer it would have to be to "motion at 90 deg to line of
NDT> sight" to keep from outrunning light that leaves towards us.
Yes, but the model isn't that the ejecta is moving faster than the
speed of light. Consider ejecta moving at 0.999c and moving toward
you.
--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
26 Feb 2005 09:10:05 AM |
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Dear Joseph Lazio:
"Joseph Lazio" <jlazio@adams.patriot.net> wrote in message
news:llbra7mkqa.fsf@adams.patriot.net...
"NDT" == N:dlzc D:aol T:com \(dlzc\) <N> writes:
NDT> My point was, if they are moving towards us in any sense, faster
NDT> than c, then the particle/body/object will outrun the light. We
NDT> could *see* nothing coming towards us. And the faster it is,
NDT> the closer it would have to be to "motion at 90 deg to line of
NDT> sight" to keep from outrunning light that leaves towards us.
Yes, but the model isn't that the ejecta is moving faster than the
speed of light. Consider ejecta moving at 0.999c and moving toward
you.
The concern appears to be "what if they are superlumenal". The standard
model doesn't have the problem I described. He has so far ignored the
"normal spectrum", which also limits the jet to sublumenal speed.
Maxwell provides the conundrum I describe, since light travels at c for all
observers, yet light leaves "forward" from an object travelling at c. He
seems to be running towards Fizeau next...
David A. Smith
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| User: "" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
26 Feb 2005 05:36:44 PM |
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N:dlzc D:aol T:com (dlzc) wrote:
Dear Joseph Lazio:
"Joseph Lazio" <jlazio@adams.patriot.net> wrote in message
news:llbra7mkqa.fsf@adams.patriot.net...
"NDT" == N:dlzc D:aol T:com \(dlzc\) <N> writes:
NDT> My point was, if they are moving towards us in any sense,
faster
NDT> than c, then the particle/body/object will outrun the light.
We
NDT> could *see* nothing coming towards us. And the faster it is,
NDT> the closer it would have to be to "motion at 90 deg to line of
NDT> sight" to keep from outrunning light that leaves towards us.
Yes, but the model isn't that the ejecta is moving faster than the
speed of light. Consider ejecta moving at 0.999c and moving toward
you.
The concern appears to be "what if they are superlumenal". The
standard
model doesn't have the problem I described. He has so far ignored
the
"normal spectrum", which also limits the jet to sublumenal speed.
Maxwell provides the conundrum I describe, since light travels at c
for all
observers, yet light leaves "forward" from an object travelling at c.
He
seems to be running towards Fizeau next...
Then wasn't Maxwell saying c'=c+v , and thus in direct conflict with
AE?
How is the increasing length per time (velocity) of these jets
measured?
SR believers might claim that the only legitimate measurement would be
that of a traveller on the jet! Otherwise, SR is decapitated right
here, with the obvious and trivial observation that velocity has NOT
shrunken the moving body!
Jim G
c'=c+v
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| User: "George Dishman" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
27 Feb 2005 04:56:06 AM |
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<jgreen@seol.net.au> wrote in message
news:1109461004.939277.271580@f14g2000cwb.googlegroups.com...
N:dlzc D:aol T:com (dlzc) wrote:
Maxwell provides the conundrum I describe, since light travels at c for
all
observers, yet light leaves "forward" from an object travelling at c. He
seems to be running towards Fizeau next...
Then wasn't Maxwell saying c'=c+v
David said "light travels at c for all observers"
hence c'=c.
http://www.fnal.gov/pub/inquiring/more/light/light_page9.html
, and thus in direct conflict with AE?
See section 6 of Einstein's original paper:
http://www.fnal.gov/pub/inquiring/more/light/light_page9.html
How is the increasing length per time (velocity) of these jets measured?
Length isn't too meaningful as the jets are a
continuous flow so there is no clear end to the
jet. Measuring the speed depends on non-uniformity
in the flow by following the progress of 'knots'
of matter. For example:
http://www.stsci.edu/ftp/science/m87/m87.html
and in particular this set of frames:
http://www.stsci.edu/ftp/science/m87/bw3.gif
Or look at the attached radio map here:
http://www.phy.duke.edu/~kolena/superluminalmotion.html
You might also practice your maths by trying
to answer the questions on that page ;-)
SR believers might claim that the only legitimate measurement would be
that of a traveller on the jet!
SR provides a set of rules for converting
measurements in one frame into another frame.
Both measurements are "legitimate" in their
respective frames.
Otherwise, SR is decapitated right
here, with the obvious and trivial observation that velocity has NOT
shrunken the moving body!
It has. Someone riding on the jet would measure
a greater distance between the same knots than
an observer at rest wrt the source and viewing
the jet perpendicular to its motion.
George
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| User: "" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
27 Feb 2005 05:04:43 PM |
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George Dishman wrote:
<jgreen@seol.net.au> wrote in message
news:1109461004.939277.271580@f14g2000cwb.googlegroups.com...
N:dlzc D:aol T:com (dlzc) wrote:
Maxwell provides the conundrum I describe, since light travels at
c for
all
observers, yet light leaves "forward" from an object travelling at
c. He
seems to be running towards Fizeau next...
Then wasn't Maxwell saying c'=c+v
David said "light travels at c for all observers"
hence c'=c.
If c'=c for ALL observers, does not l'=l for those SAME observers?
http://www.fnal.gov/pub/inquiring/more/light/light_page9.html
, and thus in direct conflict with AE?
See section 6 of Einstein's original paper:
http://www.fnal.gov/pub/inquiring/more/light/light_page9.html
How is the increasing length per time (velocity) of these jets
measured?
Length isn't too meaningful as the jets are a
continuous flow so there is no clear end to the
jet. Measuring the speed depends on non-uniformity
in the flow by following the progress of 'knots'
of matter. For example:
The view is of a train coming out of a tunnel; select a carriage (=
knot)
and measure to engine. Length is carriage -> engine velocity is
carriage
-> tunnel mouth / time
http://www.stsci.edu/ftp/science/m87/m87.html
and in particular this set of frames:
http://www.stsci.edu/ftp/science/m87/bw3.gif
Or look at the attached radio map here:
http://www.phy.duke.edu/~kolena/superluminalmotion.html
You might also practice your maths by trying
to answer the questions on that page ;-)
SR believers might claim that the only legitimate measurement would
be
that of a traveller on the jet!
SR provides a set of rules for converting
measurements in one frame into another frame.
Both measurements are "legitimate" in their
respective frames.
If we applied SR to the observed velocity length which we are seeing,
then the jet would vanish! (Travelling at c it reduces to nil)
We can see the speed of the jet by way of the increasing angle between
the source and the "top", if we have a fair idea of the distance from
here.
The passenger on the jet has NO angle to observe, and so he continues
to be mistaken in his belief that he is closer to the top than he
measures. :-)
Otherwise, SR is decapitated right
here, with the obvious and trivial observation that velocity has
NOT
shrunken the moving body!
It has. Someone riding on the jet would measure
a greater distance between the same knots than
an observer at rest wrt the source and viewing
the jet perpendicular to its motion.
similar to above
Cheers
Jim G
c'=c+v
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| User: "George Dishman" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
27 Feb 2005 06:14:57 PM |
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<jgreen@seol.net.au> wrote in message
news:1109545483.934581.52550@l41g2000cwc.googlegroups.com...
George Dishman wrote:
<jgreen@seol.net.au> wrote in message
news:1109461004.939277.271580@f14g2000cwb.googlegroups.com...
Then wasn't Maxwell saying c'=c+v
David said "light travels at c for all observers"
hence c'=c.
If c'=c for ALL observers, does not l'=l for those SAME observers?
You know better than that Jim. Remember our email
discussions
IF
speed = c
THEN
....
ENDIF
http://www.fnal.gov/pub/inquiring/more/light/light_page9.html
, and thus in direct conflict with AE?
See section 6 of Einstein's original paper:
http://www.fnal.gov/pub/inquiring/more/light/light_page9.html
How is the increasing length per time (velocity) of these
jets measured?
Length isn't too meaningful as the jets are a
continuous flow so there is no clear end to the
jet. Measuring the speed depends on non-uniformity
in the flow by following the progress of 'knots'
of matter. For example:
The view is of a train coming out of a tunnel; select a
carriage (= knot) and measure to engine. Length is
carriage -> engine velocity is carriage -> tunnel
mouth / time
The engine passed long ago and is now out of sight
but you can choose any two carriages to get the
same effect.
http://www.stsci.edu/ftp/science/m87/m87.html
and in particular this set of frames:
http://www.stsci.edu/ftp/science/m87/bw3.gif
Or look at the attached radio map here:
http://www.phy.duke.edu/~kolena/superluminalmotion.html
You might also practice your maths by trying
to answer the questions on that page ;-)
SR believers might claim that the only legitimate measurement
would be that of a traveller on the jet!
SR provides a set of rules for converting
measurements in one frame into another frame.
Both measurements are "legitimate" in their
respective frames.
If we applied SR to the observed velocity length which we are seeing,
then the jet would vanish! (Travelling at c it reduces to nil)
The jet is travelling at less than c, and what
we see is the reduced length, if measured on the
jet it would be longer.
We can see the speed of the jet by way of the increasing angle between
the source and the "top", if we have a fair idea of the distance from
here.
The passenger on the jet has NO angle to observe, and so he continues
to be mistaken in his belief that he is closer to the top than he
measures. :-)
Otherwise, SR is decapitated right
here, with the obvious and trivial observation that velocity has NOT
shrunken the moving body!
It has. Someone riding on the jet would measure
a greater distance between the same knots than
an observer at rest wrt the source and viewing
the jet perpendicular to its motion.
similar to above
Similar but the other way round.
George
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| User: "Bjoern Feuerbacher" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" AppearsInadequate |
28 Feb 2005 05:43:05 AM |
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wrote:
[snip]
If c'=c for ALL observers, does not l'=l for those SAME observers?
If you mean "length" here, then no. Why should it?
[snip]
Bye,
Bjoern
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| User: "Joseph Lazio" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
02 Mar 2005 05:46:35 PM |
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"j" == jgreen <jgreen@seol.net.au> writes:
j> The view is of a train coming out of a tunnel; select a carriage (=
j> knot) and measure to engine. Length is carriage -> engine velocity
j> is carriage tunnel mouth / time
O.k., suppose you make this measurement. Say you get 2
milliarcseconds. Suppose you also know the distance to the quasar, so
that you can convert the angular distance (in milliarcseconds) to a
linear distance (in parsecs).
Now what? You have one measurement. We don't know the velocity of
the material in the jet (other than it is probably close to c), and
you cannot necessarily use the motion of the knots, because they might
be shock waves within the jets and not reflecting the actual motion of
the material in the jet.
--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html
.
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
02 Mar 2005 06:00:48 PM |
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Dear Joseph Lazio:
"Joseph Lazio" <jlazio@adams.patriot.net> wrote in message
news:ll8y55obl0.fsf@adams.patriot.net...
"j" == jgreen <jgreen@seol.net.au> writes:
j> The view is of a train coming out of a tunnel; select a
carriage (=
j> knot) and measure to engine. Length is carriage -> engine
velocity
j> is carriage tunnel mouth / time
O.k., suppose you make this measurement. Say you get 2
milliarcseconds. Suppose you also know the distance to the
quasar, so
that you can convert the angular distance (in milliarcseconds)
to a
linear distance (in parsecs).
Now what? You have one measurement. We don't know the
velocity of
the material in the jet (other than it is probably close to c),
and
you cannot necessarily use the motion of the knots, because
they might
be shock waves within the jets and not reflecting the actual
motion of
the material in the jet.
A shock wave *would be* the momentary motion of the material of
the jet. Not saying it is bulk jet velocity, but the knot, *if
it is pressure driven*, is motion of the material at some point.
Now if it is simply excitation due to some EM pulse... exciting a
plasma...
And if it is simply superlumenal scissors...
David A. Smith
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| User: "Martin Brown" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" AppearsInadequate |
03 Mar 2005 03:00:04 AM |
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N:dlzc D:aol T:com (dlzc) wrote:
Dear Joseph Lazio:
"Joseph Lazio" <jlazio@adams.patriot.net> wrote in message
news:ll8y55obl0.fsf@adams.patriot.net...
"j" == jgreen <jgreen@seol.net.au> writes:
j> The view is of a train coming out of a tunnel; select a
carriage (=
j> knot) and measure to engine. Length is carriage -> engine
velocity
j> is carriage tunnel mouth / time
O.k., suppose you make this measurement. Say you get 2
milliarcseconds. Suppose you also know the distance to the
quasar, so
that you can convert the angular distance (in milliarcseconds)
to a
linear distance (in parsecs).
Now what? You have one measurement. We don't know the
velocity of
the material in the jet (other than it is probably close to c),
and
you cannot necessarily use the motion of the knots, because
they might
be shock waves within the jets and not reflecting the actual
motion of
the material in the jet.
A shock wave *would be* the momentary motion of the material of
the jet. Not saying it is bulk jet velocity, but the knot, *if
it is pressure driven*, is motion of the material at some point.
Not at all. The shock wave represents a position in the plasma where
there is a sudden change in flow speed and hence of pressure. This might
be due to a reflected density pulse going back down the beam from an
encounter further up with denser material.
A pretty good analogue for understanding shock waves is to watch how
traffic bunches on a busy motorway or turnpike when someone makes a
mistake, hits the breaks and all their tailgaters do the same. Traffic
may slow from 80mph to 60mph abruptly. And the shockwave pulse then
usually runs backwards against the flow of the traffic whilst a gap
opens up ahead of the instigators of the instability. The speed of the
knot tells you little or nothing about the bulk traffic speed.
There is also the possibility that the bright knots represent only the
position where the relativistic beam impinges upon denser gas/dust. In
this scenario nothing physical is moving faster than c even though the
point where the beam lights up the IGM can be. Precessing beams are a
distinct possibility and hints have been seen in some objects. eg
http://www.mpa-garching.mpg.de/HIGHLIGHT/2001/highlight0101_e.html
http://www.bu.edu/blazars/3c120.html
Regards,
Martin Brown
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
03 Mar 2005 08:19:28 AM |
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Dear Martin Brown:
"Martin Brown" <|||newspam|||@nezumi.demon.co.uk> wrote in
message news:d06jmf$kqs$1@newsg3.svr.pol.co.uk...
N:dlzc D:aol T:com (dlzc) wrote:
Dear Joseph Lazio:
"Joseph Lazio" <jlazio@adams.patriot.net> wrote in message
news:ll8y55obl0.fsf@adams.patriot.net...
"j" == jgreen <jgreen@seol.net.au> writes:
j> The view is of a train coming out of a tunnel; select
j> a carriage (= knot) and measure to engine. Length
j> is carriage -> engine velocity is carriage tunnel
j> mouth / time
O.k., suppose you make this measurement. Say you
get 2 milliarcseconds. Suppose you also know the
distance to the quasar, so that you can convert the
angular distance (in milliarcseconds) to a
linear distance (in parsecs).
Now what? You have one measurement. We don't
know the velocity of the material in the jet (other than
it is probably close to c), and you cannot necessarily
use the motion of the knots, because they might
be shock waves within the jets and not reflecting the
actual motion of the material in the jet.
A shock wave *would be* the momentary motion of the
material of the jet. Not saying it is bulk jet velocity, but
the knot, *if it is pressure driven*, is motion of the
material at some point.
Not at all. The shock wave represents a position in the
plasma where there is a sudden change in flow speed
and hence of pressure. This might be due to a reflected
density pulse going back down the beam from an encounter
further up with denser material.
A pretty good analogue for understanding shock waves
is to watch how traffic bunches on a busy motorway or
turnpike when someone makes a mistake, hits the
breaks and all their tailgaters do the same. Traffic may slow
from 80mph to 60mph abruptly. And the
shockwave pulse then usually runs backwards against
the flow of the traffic whilst a gap opens up ahead of the
instigators of the instability. The speed of the knot tells
you little or nothing about the bulk traffic speed.
I see a lot of problems with this. Communications based on a
plasma-version of a traffic jam, occurs at light speed (seeing
the brake lights). Communications based on pressure requires the
plasma to travel as fast as the knot, *at the knot*, and its
speed of sound to be altered to match the necessary velocity.
And the speed of the knot is less than the speed of traffic.
Physical alterations of the plasma stream will be speed-limited
to c or less. Granted Fizeau might extend this some (but probably
not).
There is also the possibility that the bright knots represent
only the position where the relativistic beam impinges upon
denser gas/dust. In this scenario nothing physical is moving
faster than c even though the point where the beam lights up
the IGM can be. Precessing beams are a distinct possibility and
hints have been seen in some objects. eg
http://www.mpa-garching.mpg.de/HIGHLIGHT/2001/highlight0101_e.html
http://www.bu.edu/blazars/3c120.html
I think this is superior. Superlumenal scissors, or the
incidence of two streams of matter, can be made to appear FTL.
David A. Smith
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| User: "" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
03 Mar 2005 12:04:56 AM |
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Joseph Lazio wrote:
"j" == jgreen <jgreen@seol.net.au> writes:
j> The view is of a train coming out of a tunnel; select a carriage
(=
j> knot) and measure to engine. Length is carriage -> engine velocity
j> is carriage tunnel mouth / time
O.k., suppose you make this measurement. Say you get 2
milliarcseconds. Suppose you also know the distance to the quasar,
so
that you can convert the angular distance (in milliarcseconds) to a
linear distance (in parsecs).
Now what? You have one measurement. We don't know the velocity of
the material in the jet (other than it is probably close to c), and
you cannot necessarily use the motion of the knots, because they
might
be shock waves within the jets and not reflecting the actual motion
of
the material in the jet.
At a later time, see how much the angle has increased. Trig will
calculate the velocity of the "top" as it has moved per time ref its
origin.
Jim G
c'=c+v
--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html
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| User: "Sam Wormley" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" AppearsInadequate |
27 Feb 2005 06:07:16 PM |
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Special Relativity applies.
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| User: "Bjoern Feuerbacher" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" AppearsInadequate |
28 Feb 2005 05:42:03 AM |
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wrote:
[snip]
Then wasn't Maxwell saying c'=c+v ,
No, he indeed was not saying that.
Why do you think he was?
[snip]
Bye,
Bjoern
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| User: "Chris ORiordan" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
26 Feb 2005 03:48:40 AM |
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N:dlzc D:aol T:com (dlzc) wrote:
Dear Chris O'Riordan:
"Chris O'Riordan" <coranto@hotmail.com> wrote in message
news:1109240200.587669.118790@z14g2000cwz.googlegroups.com...
The conventional explanantion for the superluminal motions observed
in
many quasar-type jets is that it is an optical illusion due to the
jets
being oriented at a fairly narrow angle to our line of sight.
...
If the jets are truly superlumenal, how is it that we can see light
from
them? Since we *do* see light from them, and their spectra are
"reasonable", the rest is "tricks of geometry". If they were
superlumenal,
the light could never leave...
David A. Smith
I had in mind a VSL (variable light speed) possible explanation, where
the jet knots would not exceed the *local* value of c. The latter
would need to be ~3 X 10^9 m/s at least in the case of quasar 3C273,
for example.
This is just a speculation, of course. I don't know why c would
increase significantly outward along the axis of a (rotating,
supermassive) black hole. Something to do with twizzled-up spacetime,
mayhap?!
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| User: "Martin Brown" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" AppearsInadequate |
24 Feb 2005 04:31:53 PM |
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N:dlzc D:aol T:com (dlzc) wrote:
Dear Chris O'Riordan:
"Chris O'Riordan" <coranto@hotmail.com> wrote in message
news:1109240200.587669.118790@z14g2000cwz.googlegroups.com...
The conventional explanantion for the superluminal motions observed in
many quasar-type jets is that it is an optical illusion due to the jets
being oriented at a fairly narrow angle to our line of sight.
And it is a very good explanation that fits the observations nicely.
...
If the jets are truly superlumenal, how is it that we can see light from
them? Since we *do* see light from them, and their spectra are
"reasonable", the rest is "tricks of geometry". If they were superlumenal,
the light could never leave...
Not quite. Provided that the beam is pointing roughly towards us and/or
not receding faster than the speed of light we can still see it easily.
If a truly superluminal jet were pointed at us the material in the jet
would arrive marginally before the light emitted from it (assuming that
it continued to emit light and stayed superluminal all the way).
But even if it were truly receding faster than the speed of light we
would still see the turbulent backwash it created in the intergalactic
medium. The high resolution 5GHz image of the radio galaxy Cygnus A
shows one relativistic jet very clearly most of the way out into the lobe.
But by far the simplest explanation of apparent superluminal motion in
quasar jets is that it is a purely geometrical line of sight effect of
beaming with standard relativistic physics.
Regards,
Martin Brown
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
24 Feb 2005 04:46:12 PM |
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Dear Martin Brown:
"Martin Brown" <|||newspam|||@nezumi.demon.co.uk> wrote in message
news:cvlkkp$2th$1@news7.svr.pol.co.uk...
N:dlzc D:aol T:com (dlzc) wrote:
....
The conventional explanantion for the superluminal motions observed in
many quasar-type jets is that it is an optical illusion due to the jets
being oriented at a fairly narrow angle to our line of sight.
And it is a very good explanation that fits the observations nicely.
...
If the jets are truly superlumenal, how is it that we can see light from
them? Since we *do* see light from them, and their spectra are
"reasonable", the rest is "tricks of geometry". If they were
superlumenal, the light could never leave...
Not quite. Provided that the beam is pointing roughly towards us and/or
not receding faster than the speed of light we can still see it easily.
If a truly superluminal jet were pointed at us the material in the jet
would arrive marginally before
We are going to pick nits here, I guess. At 6c, without "Cerenkov braking"
(my apologies to purists), "marginally before" would be 5000 years before,
for a 6000 year trip at c.
Classical Cerenkov radiation involves a medium and a moving charge.
Uncharged matter would theoretically not be subject to Cerenkov radiation
(I don't know if neutron streams are faster than c/1.4, but it would be
hard to separate them from the other particles in the mix that *are*
charged).
the light emitted from it (assuming that it continued to emit light and
stayed superluminal all the way).
And the intensity and spectrum received would be... blueshifted beyond
what? Gamma, cosmic, what? Light could not leave the surface of the face
coming at us, if it were superlumenal. 1/2 wavelength out, and the
emitting object "crashes" into the photon stream.
But even if it were truly receding faster than the speed of light we
would still see the turbulent backwash it created in the intergalactic
medium. The high resolution 5GHz image of the radio galaxy Cygnus A shows
one relativistic jet very clearly most of the way out into the lobe.
But by far the simplest explanation of apparent superluminal motion in
quasar jets is that it is a purely geometrical line of sight effect of
beaming with standard relativistic physics.
Absolutely correct.
David A. Smith
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| User: "Chris ORiordan" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
26 Feb 2005 04:05:49 AM |
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Martin Brown wrote:
N:dlzc D:aol T:com (dlzc) wrote:
Dear Chris O'Riordan:
"Chris O'Riordan" <coranto@hotmail.com> wrote in message
news:1109240200.587669.118790@z14g2000cwz.googlegroups.com...
The conventional explanantion for the superluminal motions observed
in
many quasar-type jets is that it is an optical illusion due to the
jets
being oriented at a fairly narrow angle to our line of sight.
And it is a very good explanation that fits the observations nicely.
There are key cases where it emphatically DOESN'T appear to fit, as I
mentioned in
http://www.geocities.com/chrisori2000/superjet.htm
To recap:-
(For the 7 known superluminals in 1983,) the structures did NOT in
general appear to be oriented close to the line-of-sight;
Mackay, Thompson et al suggested in 1993 that the (outer) jet of quasar
3C273 was nearly PERPENDICULAR, rather than nearly parallel, to the
line-of-sight. Superluminal motion of up to ~9.6c has been observed
along the (inner) jet;
The jet of the galaxy M87 needs to be at ~19 degrees to the
line-of-sight to explain by beaming superluminal motion of up to ~6c in
it -- but independent evidence on the jet's orientation suggests it is
at ~43 degrees to our line-of-sight.
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| User: "Joseph Lazio" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
26 Feb 2005 08:56:20 AM |
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"CO" == Chris O'Riordan <coranto@hotmail.com> writes:
CO> There are key cases where it emphatically DOESN'T appear to fit,
CO> as I mentioned in
CO> http://www.geocities.com/chrisori2000/superjet.htm
There appears to be some link rot here.
CO> To recap:-
CO> (For the 7 known superluminals in 1983,) the structures did NOT in
CO> general appear to be oriented close to the line-of-sight;
CO> Mackay, Thompson et al suggested in 1993 that the (outer) jet of
CO> quasar 3C273 was nearly PERPENDICULAR, rather than nearly
CO> parallel, to the line-of-sight. Superluminal motion of up to
CO> ~9.6c has been observed along the (inner) jet;
I can find no paper in ADS with the authors "Mackay" and "Thompson."
Perhaps you could post a reference?
CO> The jet of the galaxy M87 needs to be at ~19 degrees to the
CO> line-of-sight to explain by beaming superluminal motion of up to
CO> ~6c in it -- but independent evidence on the jet's orientation
CO> suggests it is at ~43 degrees to our line-of-sight.
Doesn't this require independent knowledge of the speed of the ejecta?
Reference?
--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html
.
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| User: "Jonathan Silverlight" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
26 Feb 2005 06:12:09 PM |
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In message <llfyzjmktn.fsf@adams.patriot.net>, Joseph Lazio
<jlazio@adams.patriot.net> writes
"CO" == Chris O'Riordan <coranto@hotmail.com> writes:
CO> There are key cases where it emphatically DOESN'T appear to fit,
CO> as I mentioned in
CO> http://www.geocities.com/chrisori2000/superjet.htm
There appears to be some link rot here.
CO> To recap:-
CO> (For the 7 known superluminals in 1983,) the structures did NOT in
CO> general appear to be oriented close to the line-of-sight;
CO> Mackay, Thompson et al suggested in 1993 that the (outer) jet of
CO> quasar 3C273 was nearly PERPENDICULAR, rather than nearly
CO> parallel, to the line-of-sight. Superluminal motion of up to
CO> ~9.6c has been observed along the (inner) jet;
I can find no paper in ADS with the authors "Mackay" and "Thompson."
Perhaps you could post a reference?
There's a paper in Nature 9 September 1993, vol 365 no 6442
"Internal structure and polarisation of the optical jet of the quasar
3C273" RC Thomson CD MacKay and AE Wright, but I don't have access
online.
--
Support the DEC Tsunami Appeal http://www.dec.org.uk/.
Remove spam and invalid from address to reply.
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| User: "Martin Brown" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" AppearsInadequate |
28 Feb 2005 05:31:47 AM |
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Joseph Lazio wrote:
"CO" == Chris O'Riordan <coranto@hotmail.com> writes:
CO> There are key cases where it emphatically DOESN'T appear to fit,
CO> as I mentioned in
CO> http://www.geocities.com/chrisori2000/superjet.htm
There appears to be some link rot here.
CO> To recap:-
CO> (For the 7 known superluminals in 1983,) the structures did NOT in
CO> general appear to be oriented close to the line-of-sight;
CO> Mackay, Thompson et al suggested in 1993 that the (outer) jet of
CO> quasar 3C273 was nearly PERPENDICULAR, rather than nearly
CO> parallel, to the line-of-sight. Superluminal motion of up to
CO> ~9.6c has been observed along the (inner) jet;
I can find no paper in ADS with the authors "Mackay" and "Thompson."
Perhaps you could post a reference?
All the ADS links I can find for 3c273 since 1995 say that the
observations are entirely consistent with a precessing relativistic jet.
There are oblique references to the discrepancy between what is seen in
VLBI at near the core out way out in the optical. eg.
http://searcht.netscape.com/ns/boomframe.jsp?query=%2BADS+%2Babstracts&page=1&offset=0&result_url=redir%3Fsrc%3Dwebsearch%26requestId%3D6b5238c53e22f25e%26clickedItemRank%3D1%26userQuery%3D%252BADS%2B%252Babstracts%26clickedItemURN%3Dhttp%253A%252F%252Fadsabs.harvard.edu%252Fabstract_service.html%26invocationType%3D-%26fromPage%3DNSCPToolbarNS%26amp%3BampTest%3D1&remove_url=http%3A%2F%2Fadsabs.harvard.edu%2Fabstract_service.html
CO> The jet of the galaxy M87 needs to be at ~19 degrees to the
CO> line-of-sight to explain by beaming superluminal motion of up to
CO> ~6c in it -- but independent evidence on the jet's orientation
CO> suggests it is at ~43 degrees to our line-of-sight.
Doesn't this require independent knowledge of the speed of the ejecta?
Reference?
Again the modellers seem to have things under control. eg
http://searcht.netscape.com/ns/boomframe.jsp?query=%2BADS+%2Babstracts&page=1&offset=0&result_url=redir%3Fsrc%3Dwebsearch%26requestId%3D6b5238c53e22f25e%26clickedItemRank%3D1%26userQuery%3D%252BADS%2B%252Babstracts%26clickedItemURN%3Dhttp%253A%252F%252Fadsabs.harvard.edu%252Fabstract_service.html%26invocationType%3D-%26fromPage%3DNSCPToolbarNS%26amp%3BampTest%3D1&remove_url=http%3A%2F%2Fadsabs.harvard.edu%2Fabstract_service.html
And being close to us it is well studied at high resolution eg
http://searcht.netscape.com/ns/boomframe.jsp?query=%2BADS+%2Babstracts&page=1&offset=0&result_url=redir%3Fsrc%3Dwebsearch%26requestId%3D6b5238c53e22f25e%26clickedItemRank%3D1%26userQuery%3D%252BADS%2B%252Babstracts%26clickedItemURN%3Dhttp%253A%252F%252Fadsabs.harvard.edu%252Fabstract_service.html%26invocationType%3D-%26fromPage%3DNSCPToolbarNS%26amp%3BampTest%3D1&remove_url=http%3A%2F%2Fadsabs.harvard.edu%2Fabstract_service.html
Regards,
Martin Brown
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| User: "Chris ORiordan" |
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| Title: Re: Superluminal Quasar Jets : The Beaming "Explanation" Appears Inadequate |
28 Feb 2005 04:40:43 AM |
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Sorry, the correct link is
http://uk.geocities.com/chrisori2000/superjet.htm , which has links to
*some* of the references.
As Jonathan Silverlight below remarks, the Nature article by Thompson,
Mackay and Wright isn't online. It appeared in 1993, and Nature hasn't
got round to putting these online yet. But, basically, the authors say
that the (outer) jet appears to be nearly parallel to the line of sight
because of the way it apparently intersects the surface of a gaseous
halo around the quasar. (Brightening of the jet coincides with
apparent edge-brightening of the halo.)
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