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I Number of galaxies in the Universe

  1. Oct 19, 2017 #21

    kimbyd

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    My understanding is that at the time, observational astronomy was not yet equipped to measure the number of galaxies to any significant degree of accuracy, so it was largely a guess. One informed by observation, but that could have been much further off than it was.

    I'm pretty sure the first solid evidence of a lower bound of around 100 billion galaxies really did come from Hubble (though with the Deep Field in 1992, not the later Ultra Deep Field, as I mistakenly said earlier).
     
  2. Oct 19, 2017 #22

    phyzguy

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    If you ask, "How many galaxies are in the observable universe?" you need to be more precise about what you are asking. If you read the link that phinds provided, the reason the estimate went up is that they decided that there were many very faint galaxies in the early universe that have since merged into larger galaxies. So if you are asking, "How many galaxies can we see?" then the proposed increase makes sense. If instead you are asking, "How many galaxies are in the observable universe now?" you will probably come up with a smaller number. Of course, you then get into issues of how you define "now" in an expanding universe.
     
  3. Oct 19, 2017 #23

    Thuring

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    Wilipedia:

    In 2016, a study published in The Astrophysical Journal and led by Christopher Conselice of the University of Nottingham using 3D modeling of images collected over 20 years by the Hubble Space Telescope concluded that there are over 2 trillion (2×1012) galaxies in the observable universe.
     
  4. Oct 19, 2017 #24

    phinds

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    And that statement in no way addresses the issues pointed out to you by phyzguy in post #22
     
  5. Oct 19, 2017 #25

    Thuring

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    It provided the recent source for the 2 trillion estimate.
     
  6. Oct 19, 2017 #26

    phinds

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    Right. Estimate of WHAT, is my point and that of @phyzguy
     
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