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The Science of Light
Stellar Spectra
IntroductionLight in ColorLaws of Light
 
  background

When light passes through a prism, it separates into the colors that make it up. White light changes to a swath of colors. This rainbow is called a spectrum. You can make spectra (the plural of spectrum) in many ways: with a prism, with drops of water (as in a real rainbow), or with gratings (like in the glasses you can get). Scientists build special instruments to separate light, usually with gratings. These instruments are called spectrographs.

When astronomers pass the light of a star through a spectrograph, they get a spectrum of the star. The spectrum looks like a regular rainbow of colors—except that there are dark lines in it. Here is a spectrum of our sun:

What's going on?

It turns out that each element absorbs light of a particular frequency—a particular color. If that element is in the cool atmosphere of the star, those atoms will absorb the light at that color and produce the line. Each element has a specific "signature"—a specific set of line.

On the next page, you will figure out the composition of some stars made specifically for this study.

Go!

 
 
 

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