For the first time, starlight from one of the Unit Telescopes (UT) that make up ESO’s Very Large Telescope (VLT) has been successfully channelled 60 metres along a tunnel leading to a new focus in the underground laboratory beneath the VLT platform. When the system is fully operational, light from all four UTs will be brought to this “convergence point”, where the ESPRESSO (Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations) high resolution spectrograph will be placed in 2017, collecting and analysing the combined light from the individual telescopes. In this way, the UTs, each of which has a diameter of 8 metres, will together equal the light collecting power of a telescope with a diameter of 16 metres. It will also be possible to use ESPRESSO with just one of the UTs, whenever all four are not needed.
To get the light from the telescope to the new focus, a new and very complex optical system was designed and installed by the Portuguese partner of the ESPRESSO Consortium. The quality of the images collected at the “convergence point” was excellent, satisfying the very challenging requirements imposed by the ambitious scientific goals of the instrument.
This is a very significant and encouraging first step in the development of ESPRESSO, a hugely sophisticated instrument, and it represents a major success for the team of engineers and astronomers working on the instrument. This early result gives the team great confidence about the performance that will eventually be achieved by ESPRESSO. In the coming months, the remaining three UTs will be connected to the focal point, after which the ESPRESSO instrument itself will be installed and observations will begin in earnest.
ESPRESSO has been under development by the ESPRESSO Consortium for the last six years. It builds on the success of the HARPS instrument on ESO’s 3.6-metre telescope at its La Silla Observatory, bringing high-resolution spectrometry to the VLT. ESPRESSO’s sensitivity means it will be invaluable in the search for rocky, Earth-like planets in distant star systems. It will also be able to undertake sensitive measurements of the fundamental physical constants of the Universe, looking in particular for any changes in them with time, and it will study in detail the chemical compositions of stars in distant galaxies.
The ESPRESSO consortium consists of: Université de Genève, Switzerland; Universität Bern, Switzerland; INAF-Trieste, Italy; INAF – Osservatorio Astronomico di Brera, Italy; Instituto de Astrofísica de Canarias, Spain; Universidade do Porto, Portugal; Universidade do Lisboa, Portugal; and ESO.