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Roser Pello's galaxy is receding at 2.3 times the speed of light

  1. Mar 2, 2004 #1


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    Roser Pello and her colleagues at the MidiPyrenees observatory
    have reported finding a z=10 galaxy

    this galaxy is currently 31.5 billion light years from us
    and is receding from us at 2.3 times the speed of light

    for more details see "the most distant object thread"
    especially links supplied by Meteor, GedankenDonuts and Nereid.
    Also a recent post in the AstronomyCosmology reference shelf sticky.

    here is a picture of Roser
    http://webast.ast.obs-mip.fr/people/roser/ [Broken]

    here is the scientific journal article she co-authored about
    this z=10 galaxy

    http://www.edpsciences.org/papers/aa/pdf/press-releases/aaga201.pdf [Broken]
    Last edited by a moderator: May 1, 2017
  2. jcsd
  3. Mar 3, 2004 #2
    Marcus there is also a very relevant QSO team that have placed their findings here:http://uk.arxiv.org/abs/astro-ph/0403040

    Contained within is, Quote:For a flat, Omega_m=0.3 and Omega_lam=0.7, Universe, we find that a double power law with luminosity evolution that is exponential in look-back time, t, of the form L*(z) exp(6.15t), equivalent to an e-folding time of 2Gyr, provides an acceptable fit to the redshift dependence of the QSO luminosity function over the range 0.4 < z < 2.1 and M_bJ<-22.5. Evolution described by a quadratic in redshift is also an acceptable fit, with L*(z)~10^(1.39z-0.29z^2).
  4. Mar 3, 2004 #3
    marcus, I have seen that in Ned Wright's page he also gives the cipher of 31.5 billion light years, but do not think that this is correct, given that before the discovery of this galaxy, our particle horizon was believed to be of 47 billion light years!
    Last edited: Mar 3, 2004
  5. Mar 3, 2004 #4


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    Hi meteor,
    I got the number 31.5 just by plugging in concordance parameters to
    Siobahn Morgan's calculator, so it is not really my number and merely
    the usual guesswork. But it is nice to know that Ned Wright posted the same estimate!

    I am not clear about how this contradicts the particle horizon being 47 or anyway something around 50 billion LY. What should be wrong?
    I would like to know your reason because it may contain an interesting idea.

    I got the 31.5 estimate by putting into Morgan's calculator the numbers
    H = 71
    Lambda = .73
    Omega (for ordinary and dark matter density) = .27
    z = 10

    then it said something like 31.48 which I rounded to 31.5

    Let us put the same numbers in the calculator and then change z to make it larger and larger, and see what happens
    (it may destroy the accuracy of the calculator! or it might converge
    to something like the particle horizon, a priori I dont know which is more likely)
    Last edited: Mar 3, 2004
  6. Mar 3, 2004 #5


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    a tough little calculator
    when I put in z=10 000 it did not blow up
    it said current distance is 46.0 billion

    so I put in z = 100 000 and it said 46.1 billion LY

    maybe it converges to something around 47
    which is what you said

    this is with H = 71
    and (0.27, 0.73)

    in some sense it seems that the number 31.5 is consistent
    with the particle horizon being around 47, or?

    URL for online cosmology calculator:
    http://www.earth.uni.edu/~morgan/ajjar/Cosmology/cosmos.html [Broken]
    Last edited by a moderator: May 1, 2017
  7. Mar 3, 2004 #6
    2.3 times? Damn, so what does this mean, time travel is possible? Maybe its a galaxy from the future instead of looking into the past
  8. Mar 3, 2004 #7


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    fortunately for everyone's sanity the recession speed associated with the expansion of space is a different kind of speed from that of local relative motion

    there are two kinds of speed and the well-known universal speed limit only applies to one type

    different people around this forum have explained and discussed it in various threads.

    as I recall the article called "Expanding Confusion" by Tamara Davis and Charles Lineweaver wasnt bad---it talked about the confusion difficulties that we all have (lay and expert alike) because of these different notions of speed---ordinary speed versus recession speed: the rate that distant objects are receding

    here's the Davis and Lineweaver article, in case it works for you:

    Maybe one way to remember it is this: nothing can ever overtake and pass a speeding photon, so in that sense nothing can go faster than light. but a distant object merely by sitting still can be getting farther from us at a rate greater than c simply due to the expansion of space (the fact that distances are increasing at a rate proportional to distance)

    all that stuff that is receding faster than c is very far away from us
    nothing ever comes whipping past the earth at some outrageous
    faster-than-c speed because that is physically impossible
    Last edited: Mar 3, 2004
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