The European Southern Observatory (ESO) has signed an agreement with a consortium led by the Leibniz Institute for Astrophysics Potsdam (AIP) to build 4MOST, a unique, next-generation spectroscopic instrument, which will be mounted on the Visible and Infrared Survey Telescope for Astronomy (VISTA) at ESO's Paranal Observatory in northern Chile. 4MOST, the 4-metre Multi-Object Spectroscopic Telescope, is expected to collect approximately 75 million spectra over its planned fifteen-year lifetime.

The agreement was signed in Potsdam, Germany, by ESO Director General Tim de Zeeuw, and by Matthias Steinmetz and Matthias Winker on behalf of the AIP. Professor Dr. Johanna Wanka, German Federal Minister of Education and Research, and Dr. Martina Munch, State Minister of Science, Research and Culture for the Land Brandenburg, were present at the signing. The German Federal Ministry of Education and Research (BMBF) supports the AIP in its work on 4MOST in the framework of "Verbundforschung" (collaborative research).

Matthias Steinmetz, scientific chairman of the AIP and director of the research branch "Extragalactic Astrophysics," stated that: "Today's agreement marks a new milestone for our institute.

For the first time, the AIP takes the lead of a consortium to execute an ESO large-scale project. This success has only been possible thanks to the scientific expertise accumulated in our institute and thanks to the tremendous engagement of our scientists, engineers and employees."

Roelof de Jong, Principal Investigator of 4MOST, added: "Exciting years are ahead of us: 4MOST is being designed to address a broad range of hot topic science cases, ranging from the assembly history of our Milky Way to the evolution of supermassive black holes in the centres of galaxies."

4MOST
4MOST, the 4-metre Multi-Object Spectroscopic Telescope, will be installed on the VISTA telescope in the position occupied by the VISTA Infrared Camera, the current workhorse instrument on VISTA, where it will provide the telescope with unique new capabilities.

The instrument is expected to start operation in 2022, when it will begin to shed light on some of today's most pressing astronomical questions, contributing to studies of the dynamics and chemical evolution of the Milky Way, measuring large numbers of active galaxies and galaxy clusters, and helping to constrain models of the accelerating universe.

4MOST will allow astronomers to study the spectral light distribution from approximately 2,400 objects simultaneously over a field of view of four square degrees - an area equivalent to 20 full Moons. 4MOST will spend the majority of its time performing spectroscopic surveys of the southern sky, collecting 25 million spectra every five years from an area of over 17,000 square degrees - more than 40 percent of the entire sky. During its planned fifteen-year lifetime it is therefore expected to provide the astronomical community with an unprecedented 75 million spectra.

Observing over the full visible light wavelength regime, 4MOST will measure the velocities of extragalactic objects on extended redshift scales hence being able to nail down the evolution of galaxies and large-scale structures in the universe.

4MOST will not only answer many outstanding astronomical questions, but it is specifically designed to complement three all-sky, space-based observatories of key European interest - Gaia, EUCLID, and eROSITA. It will additionally provide a spectroscopic complement to many other large-area surveys, including, VST, Pan-STARRS, the Dark Energy Survey, LSST, ASKAP, WISE, and PLATO.

The 4MOST consortium consists of 15 institutes in Germany, the UK, France, Sweden, Switzerland, and the Netherlands, under leadership of the Leibniz Institute for Astrophysics Potsdam (AIP).