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How blue are blue stars?

  1. Apr 20, 2013 #1
    Obviously if you looked at one it would appear white as it's so bright and stars are black bodies so emit all over the spectrum (correct me if I'm wrong). But as the sun is a yellow star, it looks yellow around it (unless that's the atmosphere of Earth getting rid of blue?) and has a yellow tinge.

    If you were placed in space at a distance in the range of a few AU, would it literally appear blue?

    If the sun were blue, and Earth's orbit were adjusted so that the new (blue) sun would appear as big as the current (yellow) sun does now, would everything have a blueish tinge?
  2. jcsd
  3. Apr 20, 2013 #2
    The direct approach is to go out at night and look at a blue star. There is an obvious difference.
  4. Apr 22, 2013 #3
  5. Apr 23, 2013 #4
    Thanks. Both good ideas. I never trust google image searching because perhaps the images are often not true colour. As for looking at stars at night, I'm sure so many of the stars seem to appear bluish, but then again I've never looked up at the sky with a telescope. Having said that, I've definitely noticed Betelgeuse looking redder from the naked eye.
  6. May 23, 2013 #5
    Our sun is actually white to our eyes. Yes stars emit in all wavelengths, but they have a peak (actually, I believe our own star has a peak in the green wavelength - but a quick look at the Planck curve explains why we don't see green stars). You are right, it's the effect of the atmosphere removing the bluer wavelegnths from our view of the sun. If you looked up at it during the day, when it is directly above you (i.e. has the least amount of atmosphere to pass through) it would seem white. But we can only really look at the sun when it is rising or setting, that is when it is easiest on our eyes. Nearer the horizon the light from the sun has more atmosphere to travel through before photons register in our eyes, meaning the bluer wavelengths are removed more, so you see it as red/orange. The reason our clouds appear white is because the light from the sun is white If the light from it were primarily purple, we'd have purple clouds!

    Stars like Betelgeuse though would appear red to you in the absence of an atmosphere.

    Great question though. Colour really is all relative to us because of our optical system.
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