Revolution in astronomy: 4MOST launches large-scale sky survey!

Revolution in astronomy: 4MOST launches large-scale sky survey!

On May 23, 2025, the 4MOST (4-Meter Multi-Object Spectroscopic Telescope) will officially go into operation. This innovative instrument is a survey facility capable of observing thousands of astronomical objects simultaneously. It will be installed on the VISTA telescope at the Paranal Observatory in Chile and aims to provide rich spectroscopic data for sky surveys and various scientific programs. Pro physics reports that 4MOST will be used in particular to study galactic archaeology, map the large-scale structure of the universe and chemical enrichment of the Milky Way.

The telescope also enables the detection of short-lived astrophysical phenomena, such as changes in the brightness of stars, supernovae, gamma-ray bursts and quasars. It has the special ability to perform both low and high resolution spectroscopy, making it a unique state-of-the-art instrument.

Technical characteristics and team

Construction of 4MOST began in 2015 and brought together the expertise of over 300 scientists and engineers from more than 15 different institutions worldwide. Important partners are the Leibniz Institute for Astrophysics Potsdam (AIP) as well as several Max Planck Institutes and universities from Germany, Australia, France, the Netherlands, Sweden, Switzerland and Great Britain. 4MOST was selected by the European Southern Observatory (ESO) to provide a modern, fiber-powered facility for spectroscopic surveys.

The telescope can simultaneously capture spectra of up to 2,400 objects over a hexagonal field of view of 4.2 square degrees. Upon commissioning, the instrument's components will be shipped to Chile, with the high-resolution spectrograph (HRS) on site as early as June 10, 2025. This is supported by the AESOP fiber positioning system, a robotic system for precise positioning of 2436 optical fibers.

Scientific significance

Not only will 4MOST provide significant data for projects such as Gaia, eROSITA and Euclid, but it will also complement existing and upcoming ground-based facilities, including the Vera Rubin Observatory and SKA. The spectroscopic magnitude limits of 4MOST are aligned with the astrometric limits of Gaia. This will make it possible to acquire spectra for Gaia's faintest astrometric targets and detect high-quality radial velocities up to 100 kpc.

Additionally, 4MOST will enable detailed chemical abundance patterns and age determinations for millions of stars. The telescope is also expected to make significant contributions to galaxy evolution and cosmology by tracking the assembly of stellar mass and dark matter over time.

Overall, 4MOST's observation strategy is ambitious. The VISTA telescope will be used exclusively for observations with 4MOST for at least five years, with 70% of the observing time allocated to the 4MOST consortium. This time is used for ten different, interconnected surveys, known as consortium surveys. In addition, 30% of the observation time is available to the ESO community. A selection of 15 community surveys were already approved by ESO in January 2022.

The official launch and a special media event are scheduled for June 10, 2025, where interested parties will have the opportunity to learn more about the telescope's scientific goals, survey strategies and operations in Chile. 4MOST is thus expected to have a revolutionary impact on many key areas of contemporary astrophysics.