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Spectroscopy: and stars Most of what is known about stars comes from spectroscopy (or the study of spectra). Spectra (rainbows of diffracted light) can come from a (hot) glowing solid, a glowing liquid or a glowing gas (star). 2 astronomical purposes: 1. Tells us the elements that make up galaxies and stars (Every element has its own unique line spectrum, like a fingerprint) 2. Tells us if galaxies and stars are moving away from us or toward us (called?) There are 3 kinds of visible spectra: Continuous, bright-line and dark-line. Continuous – unbroken band of colors from a hot source. Bright-line spectrum – also called an emission spectrum, is seen when light comes through a hot gas. Hydrogen emission spectrum Helium emission spectrum Dark-line spectrum – seen when light comes through a cold gas. (absorption spectrum) Helium absorption spectrum The dark lines are in the exact same place as the bright lines would be for the same element in a bright-line spectrum. The dark lines are formed when light The lines tell us what gases are in the atmospheres of stars. Dark-line spectrum Bright-line spectrum Hydrogen emission spectrum Stars’ (dark-line) spectra. Blueshift Redshift Red shift: when the colors of the bright line spectrum shift toward the red. ?Why important?: This means that the star or galaxy is moving away from you. Blue shift: when the colors of the bright line spectrum shift toward the blue. ?Why important?: This means that the star or galaxy is moving toward you. What does the bumper sticker mean? If the background on this bumper-sticker appears blue, you’re going way too fast! What you will see with spectroscope