Spectrographs

Spectrographs and spectrometers are used to separate light into its component colors. By studying these component colors (a science called spectroscopy), we can learn a great deal about an object — the source of light — far more than what we could glean from a photograph alone.

For instance, if a gas or some other highly absorbent component is placed in front of the light path, the rainbow pattern is interrupted by a set of dark lines characteristic of the gas. In addition, hot clouds of gas in space emit distinctive patterns of bright lines. In both cases, these bright or dark spectral lines — like signatures or fingerprints — reveal the presence of the source and its temperature, chemical composition, density, and motion. Spectrographs are fundamental to tracing how an object's composition changes as the universe evolves.