4-metre Multi-Object Spectrograph Telescope

The 4-metre Multi-Object Spectrograph Telescope, or 4MOST, is a second-generation instrument built for ESO’s 4.1-metre Visible and Infrared Survey Telescope for Astronomy (VISTA) telescope based at the Paranal Observatory in northern Chile. 4MOST will occupy the VISTA Infrared Camera (VIRCAM) position which has conducted numerous surveys in the near-infrared since 2008.

The new instrument will provide VISTA with the ability to perform large spectroscopic surveys, capturing the spectra of 2400 objects simultaneously, over an area on the sky equivalent to 20 full Moons.

According to the team behind the design and construction of 4MOST, the instrument will provide ESO and the community with a world-class optical spectroscopic survey facility that will make major contributions to many of the science areas laid out in the ASTRONET.

In particular, 4MOST will execute ten key astronomical surveys in its first five years of operation. Four of them will focus on Galactic Science Surveys to complement the work of ESA's Gaia spacecraft. The main goal of Gaia is “to make the largest, most precise three-dimensional map of our Galaxy (the Milky Way)”, and 4MOST will contribute to studies of the stellar halo and the bulge of the Milky Way.

There will also be four Extragalactic Science Surveys: 4MOST will survey Active Galactic Nuclei and galaxy clusters, and will study the evolution of galaxies and the Dark Universe (Dark Energy, Dark Matter & Black holes).

Last but not least, 4MOST will perform a deep survey of the Magellanic Clouds: given that there isn't any similar instrument in the Southern Hemisphere, this study will be unique.

Observations by 4MOST will complement several space­-based ob­servatories of prime European interest including Gaia, eROSITA, EUCLID, and PLATO, and future ground-based, wide-area survey facilities like LSST and SKA.


The authoritative technical specifications as offered for astronomical observations are available from the Science Operation page.

Site: Paranal
Telescope: Visible and Infrared Survey Telescope for Astronomy (VISTA)
Focus: Cassegrain
Type: Multi-object spectrograph
Wavelength coverage: 370–950 nm
Spatial resolution:
Spectral resolution: 4000-21000
First light date: Expected in 2023
Images taken with the instrument: No images
Images of the instrument: Link
Press Releases with the instrument: Link
Science goals: Active Galactic Nuclei, galaxy clusters, evolution of galaxies and the Dark Universe (Dark Energy, Dark Matter & Black holes) and Structure and evolution of the Milky Way.


Leibniz Institut für Astrophysik Potsdam (AIP), Germany
Australian Astronomical Observatory (AAO), Australia
Centre de Recherche Astrophysique de Lyon (CRAL), France
Institute of Astronomy, Cambridge (IoA), UK 
Max-Planck-Institut für Astronomie, Heidelberg (MPIA), Germany
Zentrum für Astronomie der Universität Heidelberg / Landessternwarte (ZAH/LSW), Germany  
Max-Planck-Institut für extraterrestrische Physik (MPE), Germany
European Southern Observatory (ESO)  
Nederlandse Onderzoekschool Voor Astronomie (NOVA), the Netherlands  
Laboratoire d’Etudes des Galaxies, Etoiles, Physique et Instrumentation (GEPI), France  
Rijksunversiteit Groningen (RuG), the Netherlands 
Uppsala universitet (UU), Sweden 
Universität Hamburg (UHH), Germany