Laser Frequency Comb
Ultra-broadband laser frequency comb observed on the spectrograph of the Southern African Large Telescope. The regular comb lines act like a ruler in optical frequency, providing a calibration scale for high-resolution astronomical spectrographs of the kind used for exoplanet hunting and fundamental cosmology. The image is rendered in false color, but with the colors representative of the actual wavelength coverage, which extends from 555 nm to 890 nm.
—Derryck T. Reid, Heriot-Watt Univ.