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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 2. Tells us if galaxies and stars are moving away from us or toward us There are 3 kinds of visible spectra: Continuous, bright-line and dark-line. Continuous – unbroken band of colors from a source sending out all visible wavelengths. Bright-line spectrum – also called an emission spectrum, is a series of unevenly spaced lines of different colors and brightness. Hydrogen emission spectrum Every element has its own unique bright-line spectrum, like a fingerprint. Helium emission spectrum Dark-line spectrum – a continuous spectrum with dark lines where light has been absorbed. (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