This picture shows the spectrum of light. You may have seen similar images in the past, but this one is something special — because it’s made of star light.
In April 2015, two so-called laser frequency combs were installed at the High Accuracy Radial velocity Planet Searcher (HARPS) planet-finding instrument of the European Southern Observatory’s 3.6m telescope at the La Silla Observatory in Chile. ESO explains what these devices and the spectra they produce are good for:
A laser frequency comb can be used as a ruler with which spectra from astronomical objects can be measured with unprecedented precision. They will allow the tiny changes in stellar velocity induced by an Earth-like planet as it orbits a star to be detected. […] The increase in accuracy made possible by this new installation should in future allow HARPS to be able to detect Earth-mass planets in Earth-like orbits around other stars for the first time.