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Is a black hole a quasar or blazar?

  1. Aug 8, 2012 #1
    Hi,

    Is Sagittarius A* the black hole a quasar or a blazar? As far as I've understood, AGNs are quasars, blazars or seyfert galaxies.

    Can someone please explain how the shockwaves/knots in the jets emitted by blackholes can be detected??


    Thanks :)
     
  2. jcsd
  3. Aug 8, 2012 #2

    mathman

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    A black hole is neither a quasar or a blazar.

    Black holes do not emit anything (ignore Hawking radiation, which is undetectable for a black hole of any significant size). You might be thinking of the radiation of the accretion disc.

    http://en.wikipedia.org/wiki/Black_hole
     
  4. Aug 8, 2012 #3

    Chronos

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    Both AGN's and quasars are believed to be powered by black holes. Blazars are a type of AGN with their jets pointed at us, making them unusually bright. Black holes, of course, emit nothing. It is the material they feast upon that produces the light show.
     
  5. Aug 8, 2012 #4
    Thanks!! :)

    What method is used to study the jets of black holes??
     
  6. Aug 11, 2012 #5
    Hi, I am new of the website. How can I post the following question to the forum?

    The velocity of the gas in M87 was measured using the emission lines of various atoms. Would the orbital motion of gas about the central black hole in M87 affect its spectrum when observed from the Earth? Can anyone answer this to me, explaining the reason of your answer? Thanks
     
  7. Aug 11, 2012 #6
    first of all, if you think your question is pertinent enough to the topic of an existing thread, you can post the question in that thread, so long as it does not "hijack" the thread (change the subject, derail it, etc.). if you think your question warrants its own thread, then simply enter the appropriate sub-forum and click on the "new topic" link near the top of the page. it'll take you to a page where you can post your message along with a title.

    as far as your question is concerned, the answer is yes. at some point in its orbit around M87, the gas in the accretion disk is traveling away from us. 180° later in its orbit, that same gas is traveling toward us. considering that the gas on the inner edge of the accretion disk (the gas closest to the black hole) is traveling at an appreciable fraction of the speed of light, the light emitted by said gas will be substantially red-shifted for the portion of its orbit during which it is traveling away from us. likewise, the light emitted by that gas will be substantially blue-shifted for the portion of its orbit during which it is traveling toward us. therefore we see an oscillation of the emission/absorption lines in the gas' spectrum between lower frequencies (longer wavelengths) and higher frequencies (shorter wavelengths).
     
  8. Aug 11, 2012 #7
    Thanks 94JZA80 for your help.
    About my question, I agree with you that the answer is yes, but if we exclude the fact that a part of the orbit of the gas is traveling away from us and another part of the orbit of the gas is traveling towards us, I mean, let pretend we don't have this specific information. If we only know that the the supermassive black hole that form the active core of M87 is a strong source of radiation made from at many wavelengths and emits a jet of energetic plasma extending at least 5000 light years and that astronomers have measured the velocity of gas which surrounds and orbits the central black hole of galaxy M87 using the emission lines of various atoms, how the orbital motion of gas about the central black hole in M87 affect its spectrum when observed from the Earth? How therefore could we see an oscillation of the emission/absorption lines in the gas' spectrum between lower frequencies (longer wavelengths) and higher frequencies (shorter wavelengths)? Might have something to do with the fact that the gas are not still but are rotating around the black hole?
    Is there another observations we could make or consider in order to answer yes to the question? Thanks!
     
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