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B Light produced by stars

  1. Jul 8, 2016 #1
    I've been recently watching videos about white light and the double slit experiment and how it creates a rainbow. It let me to some confusion and I would like some clarification.
    My questions are: Do all stars like ours produce white light? Would red giants only emit red light and blue giants only emit blue light? Why does our sun produce white light and not all the types of visible light separately?
    Some clarification would be amazing.
  2. jcsd
  3. Jul 8, 2016 #2


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    These might help:
  4. Jul 8, 2016 #3


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    The basic reason stars emit light in the first place is because they are hot. Both the intensity and peak frequency increase with increasing temperature. Hotter stars emit more light and the intensity of that light peaks at a higher frequency than cooler stars. Note that in the top graph in Dave's post, the intensity has been normalized, meaning that each star's graph is scaled so that they peak at the same vertical distance. Spica actually puts out MUCH more light than the Sun does at all frequencies, as the bottom graph shows.

    See this article: https://en.wikipedia.org/wiki/Thermal_radiation
  5. Jul 9, 2016 #4
    So is the first graph indicating that our sun emits light from all types of wavelengths because of it's temperature?
  6. Jul 9, 2016 #5


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    All stars emit light in all "types" of wavelengths

    It so happens that the sun emits light with a quite even distribution among the so called visible wavelengths.

    A star with surface temperature of 15 000 Kelvin will appear blue to us, because its spectrum contains a much larger fraction of blue wavelengths.

    In fact, when one studies stars, the opposite is done. One obtains a spectrum and thus calculate the temperature of the star

    (white light is also a biological effect, we think the sun is white because our eyes and brains have evolved on earth... the concept of color is subjective)
  7. Jul 9, 2016 #6


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    We are very subjective and a 'white' or grey surface will look white or grey to us under many different lighting conditions. It's quite amazing really. We can be looking at a 'red' sunset and things may have a reddish tinge to them but we can still recognise a grey as grey. Or brain is working overtime to be as consistent as possible with our colour perception. A vital evolutionary advantage (obviously).
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