Credit: ESO

The light of a star was dispersed according to its colours, or wavelengths, in a very long strip. The optical elements in the spectrograph chop this long spectrum in a series of shorter ones which are positioned one after the other on the two detectors of the instrument. In order to measure the wavelength with a very high accuracy, the light from a laser comb (eso0826) is also dispersed by the spectrograph, and forms a second series of lines just next to the spectrum of the star. The light from the laser comb appears as a series of dots, whose position is well known and serve as reference.

Provider: European Southern Observatory

Image Source: https://www.eso.org/public/images/harps_cc/

Curator: European Southern Observatory, Garching bei München, Germany

Image Use Policy: Creative Commons Attribution 4.0 International License