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B Is blue shift as common as red shift?

  1. Jun 25, 2017 #1
    A somewhat trivial question, but I hear of redshift a lot more than blue.

    And is possible to get a list of galaxies that display these attributes? I would like to use the data for a project.

    Thanks guys.
     
  2. jcsd
  3. Jun 25, 2017 #2

    davenn

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    well considering pretty much everything outside of our local group of galaxies is moving away from us .... yes red shift is more common

    blue shift is measured with some of our local group eg M31 that is coming towards us

    within any particular galaxy red and blue shift can be observed for the parts moving away and towards us as the galaxy rotates

    cannot find a decent graphic

    edit
    the best I could find

    m33doppler.jpg

    This image from the Very Large Baseline Array (VLBA) shows what the galaxy M33 would look like if you could see in radio waves.
     
    Last edited: Jun 25, 2017
  4. Jun 25, 2017 #3

    davenn

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    OK
    another one ......

    Capture%20d’écran%202012-09-01%20à%2003_37_55.png

    couldn't find a credit for this one
     
    Last edited: Jun 25, 2017
  5. Jun 25, 2017 #4
  6. Jun 25, 2017 #5

    fresh_42

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    Never, ever. The universe is just one thing, but do you have any idea how many radar based speed controls they have over here?
     
  7. Jun 25, 2017 #6

    Bandersnatch

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    You can query the NED database for galaxies with redshift < 0.
    https://ned.ipac.caltech.edu/ui/?q=byparams
     
  8. Jun 25, 2017 #7
  9. Jun 25, 2017 #8

    davenn

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    what are you talking about ??
     
  10. Jun 25, 2017 #9

    fresh_42

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  11. Jun 25, 2017 #10

    Vanadium 50

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    Do they? Do they catch you coming or going?
     
  12. Jun 25, 2017 #11

    fresh_42

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    Coming, they need a photo of the plate and the driver.
     
  13. Jun 25, 2017 #12

    Vanadium 50

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    Good point. But in a dozen or so states, front plates are not required.
     
  14. Jun 26, 2017 #13
    Did i miss something?

    I'm rather confused.
     
  15. Jun 26, 2017 #14

    davenn

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    it's OK
    those guys veered off-course :rolleyes:

    was there anything else relating to your original query that can be discussed
    or did it get answered well enough ?


    cheers
    Dave
     
  16. Jun 26, 2017 #15
    I think thats it. Thanks.
     
  17. Jun 26, 2017 #16
  18. Jul 8, 2017 #17
    In terms of galaxies, no. The Andromeda Galaxy is approaching us, but Galaxies not in our local group are generally receding from us.
    In terms of stars in our own galaxy, blue shift is quite common. In fact, that's how scientists figured out in which direction our sun is orbiting and rougly
    how fast the period of rotation around the center of the galaxy is.

    Stars closer to the center of the galaxy and ahead of us in thier orbits generally show a red shift- they're rotating faster than the sun and receding from us.
    Stars closer to the center of the galay and behind us in their orbits generally show a blue shift- they're rotating faster than the sun and getting closer to us.
    th?id=OIP.s5ailsyACM18sbsLpbbx6QEsC9&pid=15.jpg

    Conversely, stars in the opposite quadrants, farther from us are the opposite. Depending on your orientation, stars in Quadrants I and III may show a red shift,
    stars in Quadrants II and IV a blue shift.
     
  19. Aug 16, 2017 #18
    Sorry to revive a dead post...

    Should you have enough data, would it not be possible to create a map of galaxies that are going away or coming towards us and the direction they are moving,in order to get a rough position of the original point of expansion?

    It could also be used for universal reference points for navigation, similar to the use if pulsars.
     
  20. Aug 16, 2017 #19

    russ_watters

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    We have our relative motion with respect to the CMB we can correct for, but that doesn't give us a center of expansion, because there isn't one.

    And again: outside our local group of galaxies, all of them are moving away from us -- just not quite all at the same speed vs distance ratio.
     
    Last edited: Aug 16, 2017
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