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How do we know what stars are composed of?
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Now you can see how the light from stars and clouds of matter and gas in space tells us what elements they contain. The detailed study of the wavelengths of light emitted or absorbed by a substance or object is called spectroscopy. It is a fundamental tool, not only in astronomy, but in chemistry, where it can tell us not only what elements are present, but can help us figure the composition and structure of molecules. Click Molecules in the right-hand column to learn more.
The next video discusses spectroscopy but goes further, into what else we can learn from light about the movements of objects in space. The video comes from Crash Course Astronomy, with Phil Plait. Phil talks rapidly, so don't hesitate to pause the video to look longer at figures, or the hit your left cursor key to go back and hear something again -- each stroke takes you back about five seconds without pausing, so it's a great way to say to fast-talking Phil, "Hey, say that again!"
If you like to learn about astronomy, Crash Course Astronomy is a good place to go.
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