4-metre Multi-Object Spectrograph Telescope

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. 4MOST will go well beyond the abilities of VIRCAM, allowing higher-resolution spectroscopic observations over a wider field of view, 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 nine key astronomical surveys in the first 5 years of operation. Four of them will focus on Galactic Science Surveys to complement the work of the Gaia spacecraft. The main goal of this mission 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 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: 390–950 nm
Spatial resolution:
Spectral resolution: from 300 to 1000
First light date: Expected in 2021
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).


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