A Space & astronomy forum. SpaceBanter.com

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » SpaceBanter.com forum » Astronomy and Astrophysics » Research
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

What does it mean in astrophysics for X-rays to be reflected?



 
 
Thread Tools Display Modes
  #1  
Old January 14th 19, 06:14 PM posted to sci.astro.research
Thomas Womack
external usenet poster
 
Posts: 206
Default What does it mean in astrophysics for X-rays to be reflected?

Various articles about black holes talk about X-rays emitted near the
event horizon 'reflecting off the accretion disc'.

What kind of material is it that can *reflect* X-rays? I've worked in
X-ray crystallography, and we needed grazing incidence off very
precisely figured monocrystalline silicon to get something that
reflected X-rays at 12.7keV (selenium K line); astrophysical X-rays
seem to be more at iron K which is about half that energy, but still
generally-occuring materials either absorb or transmit them.

Is this in fact more like the process around a nuclear detonation,
where things absorb X-rays and are themselves heated to X-ray-emitting
temperatures?

Tom

[[Mod. note -- Yes, thermal re-emission is one possibility.
Compton scattering is another possibility. As you note, coherent
reflection seems unlikely.
-- jt]]
Ads
  #2  
Old January 15th 19, 07:59 PM posted to sci.astro.research
Martin Hardcastle
external usenet poster
 
Posts: 63
Default What does it mean in astrophysics for X-rays to be reflected?

In article ,
Thomas Womack wrote:
Is this in fact more like the process around a nuclear detonation,
where things absorb X-rays and are themselves heated to X-ray-emitting
temperatures?


The emission lines people talk about are X-ray fluorescence from
(relatively) cold material.

Martin
--
Martin Hardcastle
School of Physics, Astronomy and Mathematics, University of Hertfordshire, UK
Please replace the xxx.xxx.xxx in the header with herts.ac.uk to mail me

  #3  
Old January 16th 19, 03:15 AM posted to sci.astro.research
Eric Flesch
external usenet poster
 
Posts: 312
Default What does it mean in astrophysics for X-rays to be reflected?

On Mon, 14 Jan 2019, Thomas Womack wrote:
generally-occuring materials either absorb or transmit them.
[[Mod. note -- ... As you note, coherent reflection seems unlikely.


Does not radiation reflection *always* consist of absorption &
re-transmission? By "coherent reflection", JT seems to imply
preservation of the original photons. But photons don't "bounce" in
the rubber-ball sense, right?

I'm reminded of transferring money in the banking system -- it's not
the same dollar that moves around, money is "fungible" in the sense
that a dollar has no individual identity as such. I am suspecting
that photons are fungible in the same way, but that that element is
not built into the model of light as we know it.

[[Mod. note -- My apologies for being unclear. What I was trying to
get at with the phrase "coherent reflection" (which in hindsight was
a poor choice of words on my part) was "reflecting like a beam of
optical light from a mirror, with angle-of-reflection =
angle-of-incidence".

As to whether elastic scattering of any sort yields the "same" photon,
I suspect that you're right and that photons don't have an individual
identify. In fact, I suspect that "the same photon" isn't even a
meaningful concept in quantum optics. But my knowledge of quantum
optics is alas very small, so I can't speak with any authority on
this....
-- jt]]
  #4  
Old February 5th 19, 03:50 PM posted to sci.astro.research
Steve Willner
external usenet poster
 
Posts: 1,157
Default What does it mean in astrophysics for X-rays to be reflected?

In article ,
Eric Flesch writes:
As to whether elastic scattering of any sort yields the "same" photon,
I suspect that you're right and that photons don't have an individual
identify.


Doesn't this have to be true? Wouldn't the Planck law have a
different form if photons were distinguishable? When I studied
thermodynamics, there were four cases: particles could be
distinguishable or indistinguishable, and they could or could not
occupy the same state. (Distinguishable particles that can occupy
the same state are rare.)

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Possible Origin of Cosmic Rays Revealed with Gamma Rays (Forwarded) Andrew Yee News 0 November 5th 04 05:54 AM
Possible Origin of Cosmic Rays Revealed with Gamma Rays (Forwarded) Andrew Yee Astronomy Misc 0 November 5th 04 05:53 AM
Galactic Center X-Rays and Gamma Rays Confounds Astrophysicists Imperishable Stars Misc 2 September 25th 04 11:48 PM
Spectral Analysis of Reflected Light ?? G=EMC^2 Glazier Misc 8 August 18th 04 03:16 PM
Moon as reflected light G. Carlson Amateur Astronomy 60 February 16th 04 09:41 AM


All times are GMT +1. The time now is 09:28 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright 2004-2019 SpaceBanter.com.
The comments are property of their posters.