Results 1 to 10 of 10

Thread: X-ray Types

  1. #1
    Join Date
    Sep 2003
    Posts
    2,608
    Hi there,

    There are to my knowledge 2 different ways of generating X-rays. Thermal (by millions of K) and non-thermal (by electric fields). How can we measure the difference between these types (is there even a difference) and are there other ways to measure million degree temperatures?


    Cheers.

  2. #2
    Join Date
    Jul 2005
    Location
    Massachusetts, USA
    Posts
    22,082
    Originally posted by VanderL@Jun 12 2004, 10:37 AM
    There are to my knowledge 2 different ways of generating X-rays. Thermal (by millions of K) and non-thermal (by electric fields). How can we measure the difference between these types (is there even a difference) and are there other ways to measure million degree temperatures?
    For an individual photon, there is no way to know. If there is a source of many photons you can tell a lot.

    - Thermal X-rays can be identified by the roughly blackbody shape to the spectrum of photons.
    - X-rays generated by the flourescence of materials exposed to gamma rays [or other ionizing radiation] have distinct emision energies [this is the photons given off after the fact as electrons drop back down to their lowest energy states in heavy atoms.
    - The X-rays that come from the sudden slowing down [or changing directions] of electrons [or other charged paticles] at a given energy has a characteristic spectrum with a peak at the highest energy, and a tail as the energy decreases.
    - There are other effects that can cause X-rays, they each have a different characteristic spectrum.
    Forming opinions as we speak

  3. #3
    StarLab Guest
    I believe there is a conversion factor between electronVolts and Kelvins, but I'm not sure what it is...

  4. #4
    Guest Guest
    Hi Antoniseb, thanks for the quick reply.
    Now I'm quite confused, apparently there are many ways to generate X-rays. How can we tell the difference when the processes that generate them are diverse and acting at the same time. For instance, the X-ray glow that can be found in galaxies are interpreted as thermal. So the gas is said to be millions of degrees. Suppose these X-rays are non-thermal and caused by electric fields, but the fields are not simple and the characteristic spectrum is therefore absent. Is it possible to mistake non-thermal X-rays for thermal X-rays?


    Cheers.

  5. #5
    Join Date
    Jul 2005
    Location
    Massachusetts, USA
    Posts
    22,082
    Originally posted by Guest@Jun 12 2004, 03:29 PM
    Is it possible to mistake non-thermal X-rays for thermal X-rays?
    Suppose that there were some thermal source of electrons, and that they were hitting heavy atoms and stopping suddenly, giving off X-rays. These X-rays would have a spectrum that is pretty close to a blackbody spectrum for X-rays. But then, that would basically be a thermal source.

    If you have an explicit physical situation that you can describe, we can discuss whether the X-rays can be identified as coming from one source or another.
    Forming opinions as we speak

  6. #6
    Join Date
    Sep 2003
    Posts
    2,608
    Thanks Antoniseb,

    Ok, examples. Well, electrons accelerated in an electric field hit atoms and the atoms emit X-rays. If this is happening how do you distinguish this X-ray signal from thermally accelerated atoms smashing into each other? In effect you can't "see" the electric field, so how do you know it's not there?
    What we hear about are a lot of X-ray sources from all over the Universe. Chandra shows them in detail. Almost always they are assigned "thermal", hence the "million degree temperatures" that are often cited. I wonder if this is always the case, and I'm curious where the non-thermal X-rays can be found.
    I know comets emit them, Jupiter is active, lightning can produce X-rays (presumably non-thermal).
    So, where else do I look for non-thermal X-rays.

    Cheers.

  7. #7
    Join Date
    Jul 2005
    Location
    Massachusetts, USA
    Posts
    22,082
    Originally posted by VanderL@Jun 13 2004, 10:14 AM
    Ok, examples. Well, electrons accelerated in an electric field hit atoms and the atoms emit X-rays. If this is happening how do you distinguish this X-ray signal from thermally accelerated atoms smashing into each other?
    If you have electrons accelerated across an electric field, either the electric field is short-lived or you have some kind of charge imbalance with some unknown mechanism keeping the charge out of balance while electrons are drawn into it.

    In either case you are most likely going to have a fairly constant potential from electron source to target atoms, and the X-rays will be emitted at relatively discrete energies. This is very different from the thermal spectrum. In the case of electro-magnetic oscilations, you'll get some obvious variability.

    Do you have an idea what natural phenomena could cause such an electric field? I can't picture one yet.
    Forming opinions as we speak

  8. #8
    Join Date
    Sep 2003
    Posts
    2,608
    Do you have an idea what natural phenomena could cause such an electric field? I can't picture one yet.
    Wherever magnetic fields can be seen moving around there are currents and electric fields. The Sun's surface is a good example. There is lots of activity there. We can see the +ions accelerated away from the Sun (their speed is increased, the further away they are), so I see a field acting there, because there's no other way those particles are accelerated. And Jupiter and comets are also emitting X-rays, can't be enough heat there, I imagine.

    Cheers.

  9. #9
    Join Date
    Jul 2005
    Location
    Massachusetts, USA
    Posts
    22,082
    Originally posted by VanderL@Jun 13 2004, 12:22 PM
    Jupiter and comets are also emitting X-rays, can't be enough heat there
    Jupiter's X-rays come at specific energies, indicating that they are from electrons rejoining highly ionized atoms such as Oxygen VI. These ions are occuring because of Jupiter's magnetic field and aurora capturing solar wind and driving it into the atmosphere at the poles. There is also so X-ray coming from Jupiter because of lightning and electrical storms, but these are mostly absorbed by the Jovian atmosphere.

    These X-rays can easily be distinguished from thermal ones. If the X-rays from the hot gas in dense galactic structures was caused by a similar phenomenon, it would be more localized, and it would have distinct lines in its spectrum, but it is neither of these things.
    Forming opinions as we speak

  10. #10
    Join Date
    Sep 2003
    Posts
    2,405
    Do you have an idea what natural phenomena could cause such an electric field? I can't picture one yet.
    The accretion disk around a black hole or a star about to go to a SN1A state is expected (at least by me) to be highly ionized thereby setting in motion feedback loops leading to ever increasing ionization and stronger electric and magnetic fields and synchrotron radiation across the spectrum (including the the X- and gamma ray portions of the spectrum). Would these sources transmit continuous spectra with the peak energy equivalent to very high tempratures. Is the temperature signature of a source relatable to the mean kinetic energy of the plasma particles that caused them to lose the electrons for which their recapture is the actual emitter of the photons or are we discussing a more continuous emission phenomenon?

Similar Threads

  1. Four Types of People - Which are You?
    By mugaliens in forum Off-Topic Babbling
    Replies: 4
    Last Post: 2008-Nov-02, 03:58 PM
  2. SC2 Planet types
    By m1omg in forum Space/Astronomy Questions and Answers
    Replies: 0
    Last Post: 2008-Oct-15, 04:35 PM
  3. For you Aeronautical types...
    By Mister Earl in forum Off-Topic Babbling
    Replies: 3
    Last Post: 2008-Feb-26, 09:10 PM
  4. Types of mass
    By TheBlackCat in forum Space/Astronomy Questions and Answers
    Replies: 27
    Last Post: 2006-Jul-02, 01:50 AM
  5. Types Of Planets
    By imported_Ziggy in forum Space/Astronomy Questions and Answers
    Replies: 3
    Last Post: 2004-Jun-05, 08:28 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •