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Spectrograph to measure the Sun's light

  1. Dec 15, 2014 #1
    Hi, everyone. I am researching on a variety of different Physics topics to conduct my Extended Essay on.

    I was thinking, what if I made a spectrograph to measure the sun's light? Surely I'd be able to get emission and absorption lines which will more or less portray something about the sun's characteristics.

    The things is, I'm not really sure what I could get out of it once I decide to push through with the experiment. What research question could I formulate?

    Much thanks,
    (Grade 11)
  2. jcsd
  3. Dec 15, 2014 #2


    Staff: Mentor

    I don't know of anything new that you might discover. However confirming what is known is a useful exercise.

    I found this writeup that might provide you with some ideas:


    Any experiment you do, you could estimate the range of error in your equipment. take numerous measurements...
  4. Dec 15, 2014 #3


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    Composition of the Sun's atmosphere?
  5. Dec 15, 2014 #4

    Vanadium 50

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    Speed of the rotation of the sun.
  6. Dec 15, 2014 #5
    How do i measure the speed of the rotation of the sun using that experimental set-up?
  7. Dec 15, 2014 #6


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    If you have the angular resolution to do so with your equipment, compare the doppler shifts of the spectra from opposite sides of the sun.
  8. Dec 15, 2014 #7


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    You could use it to estimate the temperature of the Sun by looking at the amplitude of the spectral components. You could compare it with the spectrum of some of the brightest stars if your measuring equipment is sensitive enough (Digital camera?)
    How about the scattering effect of the Earth's atmosphere? Looking at the sky at different elevations and at different times of day.
    The sky's the limit har har!
  9. Dec 15, 2014 #8
    If i remember correctly, you could estimate the temperature on the sun by watching the bordering of the spectral line. But is just a "crude" measurement ...
  10. Dec 15, 2014 #9


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    Oh yes. You need to do some measurements with some instrument if you want to improve on what you eyes tell you. The handiest instrument for most people is a digital camera. If you can turn the exposure control to Manual and turn off the auto colour balance then the Pixel (RGB) values from picture to picture can be more validly compared. Iy would be relatively easy to see the peak of the spectral curve of sunlight (roughly) and compare it with the curves of bright stars, tungsten lights, halogen lights.
    But a camera has three sensor arrays and what you really need is a light sensor that has equal sensitivity to all visible wavelengths. But it could be a start for a useful bit of work.
    I have just re-read your quote. Did you mean 'broadening', rather than bordering? I think you would need good resolution for your spectrograph and that is unlikely. If it were that good it would probably be a spectrometer.
    Last edited: Dec 15, 2014
  11. Dec 16, 2014 #10
    :s Damn auto-correction! yhea, broadening of the spectral line. By the way, indeed she would need a spectrometer, i think it's quite impossible to measure the width of a spectral line with a spectrograph.
  12. Dec 17, 2014 #11


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    Maybe you could compare your results to those of a space telescope, and spectrographs from other parts of the world (I'm guessing these are available on line), to see what absorption lines are added, and therefore what elements are present, in the atmosphere at your location at the time of your measurement?
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