An instrument that disperses light from celestial objects into its component wavelengths and records the resulting spectrum, revealing information about temperature, composition, motion, and other physical properties. Unlike a spectroscope for visual observation, a spectrograph permanently records spectra for detailed analysis.
From Latin 'spectrum' (appearance, image) and Greek 'graphein' (to write, record). The term emerged in the late 19th century as astronomers developed photographic methods to record stellar spectra, distinguishing these recording instruments from earlier visual spectroscopes used for direct observation.
A spectrograph is like a cosmic DNA analyzer - it breaks starlight into its rainbow components to reveal what stars are made of, how hot they are, and how fast they're moving! The dark lines in stellar spectra are like fingerprints of different chemical elements, and this technique discovered that the universe is made of the same stuff as Earth, just in different proportions.
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