Light and Astronomy

1. A hot object or hot dense gas (like a star) produces a continuous spectrum -- the complete "rainbow" of colors without any dark lines in it.

2. A hot rarefied gas produces an emission line spectrum -- a series of
bright lines on a dark background.                    

3. Light passing through a cool gas (like the cool gas in a star's atmosphere) produces an absorption line spectrum -- dark lines along certain colors of the rainbow.

(the above is courtesy Terry Herter's website)

The Sun's absorption line spectrum

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