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I Why don't any stars "look" red? red shift

  1. Oct 14, 2016 #1
    Universe is expanding/galaxies moving away from each other and far away galaxies are moving away from us faster. so the light is redshifted. .."at very large redshifts, much of the ultraviolet and visible light from distant sources is shifted into the infrared part of the spectrum. This means that infrared studies can give us much information about the ultraviolet and visible spectra of very young, distant galaxies" If some stars/galaxies are so red shifted that viewing infrared shows more -- why do some stars not "look red"? When my kids look at sky at night - stars all look cosmic latte. this question came up.... I can't figure this out, so I'm posting. thx!!
     
  2. jcsd
  3. Oct 14, 2016 #2
    The stars you see at night are the ones in our own galaxy. These stars are not expanding away from us.
    If you had good enough eyes to see stars in other galaxies, you'd see them as more red.
     
  4. Oct 14, 2016 #3
    oh! thank you! that was easy. what a great forum - my first post. I should have probably thought of that ..... but how nice to get a such a quick answer to something. :)
     
  5. Oct 14, 2016 #4

    Vanadium 50

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    Also, before trying to figure out why something is true, it is important to figure out if it is true. Many stars look reddish. Betelgeuse and Antares are two that are relatively easy to find in the sky. Betelgeuse is particularly nice because it is in Orion, which also has Rigel as a bright star of a different color. Betelgeuse is reddish and Rigel is blueish.
     
  6. Oct 15, 2016 #5

    Ken G

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    And if your kids ask you why some stars are indeed red, you can tell them it is because their surface temperature is only red-hot, rather than white-hot (the latter being a higher surface temperature, like the filament in a light bulb compared to an element on an electric stove). And if your kids ask you why hotter things look whiter, tell them it is because light comes in tiny bundles of energy called photons, and the bluer ones have more energy per photon and require a higher temperature to make. Having curious kids will lead you into all kinds of interesting discoveries!
     
  7. Oct 15, 2016 #6
    Isnt the redshift of anything an amateur telescope can see too small to notice anyway?

    Wouldn't even fast moving galaxies still appear white to our eyes? Galaxies aren't just putting off visible light, it's putting out UV too. The entire spectrum just shifts over, but we'd still perceive it as white until it got to such a speed where you hit a lull in the frequency. The hydrogen line is used to identify the exact redshift, not visual cues. Personally, I think Andromeda looks blueish.

    Google Andromeda is UV, it's both really gorgeous and shows my point. It's not quite as bright, but if we were shifted into that spectrum a little, our eyes and brains would still see mostly white.
     
  8. Oct 15, 2016 #7

    Ken G

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    Indeed Andromeda is moving toward us anyway, but more to the point, you are correct that only distant quasars have enough redshift to appear red to our eye, if we could even see one peering through an extremely powerful telescope at a perfect site.
     
  9. Oct 15, 2016 #8

    Chronos

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    A reddish tint to distant galaxies is evident in some of the HST deep field photos. The HST is, of course, the finest known available imaging platform, being of fairly large aperature and operating far beyond earth's atmosphere. You may wish to show some of those images to the little ones to reinforce the concept of redshift. You can simulate the effect by overlaying images of nearby galaxies with a reddened transparency.
     
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