Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Highest known blue shift

  1. Nov 4, 2005 #1
    What is the highest known blue shift?
     
  2. jcsd
  3. Nov 4, 2005 #2

    SpaceTiger

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The largest blueshift that I could find that wasn't listed as a probable error:

    KISSBx 08

    I would still interpret it with caution, however. Other heavily blue-shifted objects are listed here:

    NED search
     
  4. Nov 5, 2005 #3
    thanks these are pretty large blue shifts. Would a jet from a black hole have a higher blue shift? Is there more than one way to create a blue shift, like what if light is comming in from an area that is more "stretched" than our area?
     
  5. Nov 5, 2005 #4

    SpaceTiger

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Interesting question. Yes, in theory, a jet could exhibit a large blueshift, even at very large distances, but they're never actually measured that way. When you're looking down a jet from a quasar or active galactic nucleus, the object is called a "blazar". These blazars can have high gamma factors (i.e. velocities very near c), but their spectra are completely featureless. The lack of features in the jet spectrum means that when we measure the redshift of the blazar, the only spectral features that might be available would be from the host galaxy or quasar. Neither of these things is moving towards us with relativistic velocities, however, so the blazar is given a net redshift.

    Anyway, the short answer is yes, there are probably jets whose radiation is blueshifted, but it doesn't go into the catalogs as a "blue-shifted" object.


    I'm not quite sure what you mean by more "stretched". The only other blueshifting method that I can think of would be a "gravitational blueshift". This could occur if the object were very nearby and in a shallower potential well than we are (like from a satellite to the earth's surface). This effect would be pretty much irrelevant for astronomical purposes, though.
     
  6. Nov 5, 2005 #5
    huh, wierd stuff. I didn't know what the spectrum is like for jets. I suppose that there is no matter in the form of an atom when it's comming out of a black hole, quasar, or galactic center because of the violent nature of the environment there, but I thought there would be a point far out enough from the source where matter starts to condense into atoms... I guess if it does, it probably doesn't emit light? Then again if it did, we could see absorbtion lines from it, so I guess thats not the case. Thats interesting.

    I was thinking along the lines of the stretchability of space-time and how it's "stretched" in the middle of two masses, and "compacted" close to each mass. So I can use the term potential well when speaking of gravity? cool! this makes more sense. Is the space in a void between galactic clusters at a higher potential than the space inside a galactic cluster? meaning, when light traverses into a void from a cluster, it goes "uphill" and when it goes into another cluster it goes back "downhill" into that cluster, so the redshift from going up is canceled by the blue shift from going down, assuming the two galactic clusters have the same "depth" of a potential well? (leaving out the redshift from expansion)
     
    Last edited: Nov 5, 2005
  7. Nov 5, 2005 #6

    SpaceTiger

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The jet will certainly shock the intergalactic medium, but any such line emission would be swamped by synchrotron radiation from the relativistic jet.


    Well, the spectra might show absorption lines, but with this alone, there's no way to be sure if the absorption is local or intervening. Since blazars are observed at cosmological distances, they often show absorption lines from gas along the line of sight.


    The appropriateness of the term "potential" in GR is being debated in this thread:

    relativity potentials

    Locally, there doesn't seem to be much disagreement that we can have a meaningful definition of "potential". At cosmological distances (such as to voids), the redshift from expansion would swamp any other gravitational effects, so it's not really a concern here.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Highest known blue shift
  1. Blue-shifted Galaxies (Replies: 19)

  2. Red and Blue shift (Replies: 11)

Loading...