The 4MOST consortium has been selected by the European Southern Observatory (ESO) to provide the ESO community with a fibre-fed spectroscopic survey facility on the VISTA telescope with a large enough field-of-view to survey a large frac­tion of the southern sky in a few years. The facility will be able to simultaneously obtain spectra of ~2400 objects distributed over an hexagonal field-of-view of 4 square degrees. This high multiplex of 4MOST, combined with its high spectral resolution, will enable detection of chemical and kinematic substructure in the stellar halo, bulge and thin and thick discs of the Milky Way, thus help unravel the origin of our home galaxy. The instrument will also have enough wavelength coverage to secure velocities of extra-galactic objects over a large range in red­shift, thus enabling measurements of the evolution of galaxies and the structure of the cosmos.

This exceptional instrument enables many science goals, but the design is especially intended to complement three key all­-sky, space­-based ob­servatories of prime European interest: Gaia, Euclid, and eROSITA. Such a facility has been identified as of critical importance in a number of recent European strategic documents (Bode et al., 2008; de Zeeuw & Molster, 2007; Drew et al., 2010; Turon et al., 2008) and forms the perfect com­plement to the many all­-sky survey pro­jects around the world.

4MOST is currently in its Manufacturing Phase with an expected start of science operations in 2022. The ESO community will be able to express their interest to use the 4MOST Facility for Public Surveys through a Call for Letters of Intent expected to be released in the summer of 2019.



4MOST enables many science goals, but our design is especially intended to complement a number of key large-area, space­-based ob­servatories of prime European interest: Gaia, eROSITA, Euclid, and PLATO, and future ground-based, wide-area survey facilities like LSST and SKA.

Read more about the 4MOST science capabilities


To reach maximum impact, 4MOST will operate continuously for an initial five-year Public Survey delivering spectra for ≥25 million object over ≥15 000 square degrees.

Read more…


The 4MOST facility will be running spectroscopic Public Surveys on VISTA all the time, and consists next to the instrument also of all the software to schedule and observe many surveys in parallel and the data management system to reduce, analyze, validate and publish all the data including higher-level data products (radial velocities/redshifts, stellar parameters, abundances, etc.).

More information about the facility


The 4MOST consortium consists of 15 institutes in Germany, Australia, France, the Netherlands, Sweden, Switzerland, and the UK, under leadership of the Leibniz-Institut für Astrophysik, Potsdam (AIP).

See all consortium partners and their roles