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Thread: Aging galaxies

  1. #1
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    Aging galaxies

    Do galaxies look different halfway to the Hubble Horizon? Are they bluer in color, for example? Or are they more/less likely to be barred spirals? Or changing in size? Anything besides likelihood of quasar activity declining?

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    The article below is from last Nov when news came out about the oldest galaxy yet discovered, at 12.8 Billion Years. Half way down it has pics of this galaxy which to me resembles a reddish yellow rose. The pics are fuzzy due to the optical "magic" of gravity bending light at mind boggling distances.

    https://www.usatoday.com/story/tech/...rse/836445001/

  3. #3
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    Quote Originally Posted by Spacedude View Post
    The article below is from last Nov when news came out about the oldest galaxy yet discovered, at 12.8 Billion Years. Half way down it has pics of this galaxy which to me resembles a reddish yellow rose. The pics are fuzzy due to the optical "magic" of gravity bending light at mind boggling distances.

    https://www.usatoday.com/story/tech/...rse/836445001/
    Remember it is strongly redshifted. If there are a lot of O and B stars lighting it up, they will resemble M stars in this one.

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    Quote Originally Posted by Tom Mazanec View Post
    Do galaxies look different halfway to the Hubble Horizon? Are they bluer in color, for example? Or are they more/less likely to be barred spirals? Or changing in size? Anything besides likelihood of quasar activity declining?
    Halfway? Not as different as you'd expect, but as you note, some minor differences in the populations. The object spacedude pointed to is 90-something percent of the way to the Hubble horizon. At THAT time galaxies looked very different, with lots more splotchy irregular galaxies illuminated brightly by giant star-forming regions and lots of blue stars. By halfway (z~1) galaxies had pretty much settled down, and the period of rapid star formation and frequent galactic mergers was mostly done.
    Forming opinions as we speak

  5. #5
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    Quote Originally Posted by antoniseb View Post
    By halfway (z~1) galaxies had pretty much settled down, and the period of rapid star formation and frequent galactic mergers was mostly done.
    Specifically, the rate of star formation peaked some 8 billion years ago, and then declined by a factor of around ten to its present value.
    Everyone is entitled to his own opinion, but not his own facts.

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