Comb modes of the ESPRESSO-AstroComb are projected onto a screen by means of an echelle spectrograph. Source: Menlo Systems
Light reaching the four main astronomical telescopes that form the Very Large Telescope (VLT) operated by the European Southern Observatory (ESO) on top of the Cerro Paranal in Chile, has been combined in a single spectrograph for the first time. This feat was facilitated by an AstroComb developed by Germany’s Menlo Systems, which allowed merging the light captured by all four 8.2-m mirrors into a single image.
The frequency comb — a collection of tens of thousands of equidistantly spaced laser lines — was generated and fed into the newly developed ESPRESSO spectrograph in parallel with the collected starlight. Both the starlight and the frequency comb are then separated into their spectral components by passage through a large diffraction grating and projected onto a CCD imaging sensor. The individual teeth of the comb are then revealed and can then be used like a ruler to assign precise frequencies to the starlight's spectral absorption lines.
Astrophysicists plan to use the ESPRESSO spectrograph to search for and characterize Earth-like exoplanets. Minimal shifts in the spectral lines of stars can now be detected with the AstroComb. Such dynamic changes can disclose whether or not a given star actually hosts planets, and they can be used to determine the orbital periods of exoplanets, their distances from their parent star and their sizes.
