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I Why do galaxy and galaxy clusters look so colorful?

  1. Jun 24, 2017 #1
    Why do galaxy and galaxy clusters look so colorful?
     
  2. jcsd
  3. Jun 24, 2017 #2

    phinds

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    And what makes you think they are? Internet photos? Most of those are color enhanced with a combination of overlays from varying frequency ranges shifted to the visible.
     
  4. Jun 24, 2017 #3
    Yes. Are the colours in these pictures completely unreal? I thought there must be some 'atomic physics and spectroscopy theory' behind these beautiful pictures.
     
  5. Jun 24, 2017 #4

    phinds

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    We've had several posts here on PF on exactly this issue. As I recall, there are more true color pics out there than I had expeced but I have no idea how to tell which is which. I suggest a forum search.
     
  6. Jun 24, 2017 #5
    A lot of the photography has to be adjusted to make a meaningful image to a human.
    X ray images and radio images are not comprehensible to us without that, other than just as numerical data.
     
  7. Jun 24, 2017 #6

    davenn

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    Many in that set are accurate colours ......

    ad6a7af4ec2b041d0b9a74f72cd33507.jpg

    06be2886d972b643faa6b54ae196d273.jpg

    eea0b03ac7107a9b35630e9deba92a99--planes-group.jpg


    many have been severely enhanced and no longer look like reality

    2ef6f797d38c9f8e2afef17753304a60--phone-wallpapers-space-iphone-wallpaper.jpg

    7ed86a288e4940a29d21981c7d664f68.jpg

    74481d2c7ea93431887797e2fe7e42bb--galaxy-universe-the-universe.jpg


    and there are also a number of pure artist's impressions there too .... that is, not actual astro images

    There is a lot of colour out there with the variety in composition of the gasses in the nebula
    the colour/temperature of the star illuminating that gas

    Dave
     
  8. Jun 24, 2017 #7

    Drakkith

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    I would say that most pictures of galaxies and galaxy clusters are decent approximations of what they would look like if your eye could gather enough light to make them bright enough to see the colors. We don't usually image galaxies with narrowband filters, but with broadband filters, producing images similar to what a normal DSLR camera creates. Still, many of these pictures have had their colors enhanced, so the color contrast wouldn't be as high as you usually see in pictures.

    Pictures of nebulas are far more likely to be false color. This is because nebulas often emit light predominantly in a handful of specific wavelengths instead of over a broad spectrum like stars (and galaxies) do. A popular set of narrowband filters used to image nebulas consists of Hydrogen-Alpha (HA), Oxygen-3 (OIII), and Sulfur-2 (SII) filters. HA and SII both pass light in the red part of the visible spectrum, while OIII passes light in the blue-green part. During processing, we often assign these narrowband images a different color than that which they imaged. The so called "Hubble palette" makes SII = red, HA = green, and OIII = blue to produce full color pictures.
     
    Last edited: Oct 15, 2017
  9. Jun 25, 2017 #8

    sophiecentaur

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    Cor! I wish my telescope was as good as yours. :-p
     
    Last edited: Jun 25, 2017
  10. Jun 25, 2017 #9

    phinds

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    davenn cheats ... he knows stuff.
     
  11. Jun 25, 2017 #10

    davenn

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    hahaha :biggrin:

    but I tell you something .... It doesn't take being on PF for very long to realise there are a lot of people that know a lot more stuff ! :smile:
     
  12. Jun 25, 2017 #11

    sophiecentaur

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    All those clever clogs who actually KNOW Maths! V humbling.
     
  13. Jun 25, 2017 #12

    davenn

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    Uh huh .... maths and I do not have a good relationship ...
    not being able to do the required two first year maths papers at uni is what stopped me finishing my BSc in geology :frown:
     
  14. Jun 25, 2017 #13

    Drakkith

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    Don't worry. I hear people going into geology usually have a 'rocky' start.
     
  15. Jun 25, 2017 #14

    sophiecentaur

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    Followed by in depth study?

    DON"T START!!!!
     
  16. Jun 25, 2017 #15

    phinds

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    Well, of course, since they are striving for cavernous knowledge
     
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