4MOST marks first light at ESO's Paranal Observatory
Unlike conventional telescopes that capture single images, 4MOST records the spectrum of each observed object - splitting its light into 18,000 colour components to reveal its chemical composition, motion, and physical properties. Using 2,436 optical fibres - each thinner than a human hair - the instrument can simultaneously observe thousands of celestial targets across a 2.5-degree-wide field of view, five times the apparent diameter of the Moon.
Developed under the leadership of the Leibniz Institute for Astrophysics Potsdam (AIP), 4MOST is the largest multi-object spectroscopic survey facility in the southern hemisphere. Its design, which began in 2010, combines a wide field of view, high spectral resolution, and massive parallel observing capability - enabling it to survey tens of millions of stars and galaxies over its expected 15-year lifetime.
4MOST Principal Investigator Roelof de Jong, head of AIP's Milky Way section, commented: "It is incredible to see the first spectra from our new instrument. The data looks fantastic from the start and bodes well for all the different science projects we want to execute. That we can catch the light that has travelled sometimes for billions of light years into a glass fibre the size of a hair is mindboggling."
Project Manager Joar Brynnel added: "Reaching this milestone is a wonderful achievement after more than a decade of intensive efforts. It is hard to put in words the excitement realizing that the facility not only meets, but even exceeds the required performance."
AIP's Scientific Director, Prof. Dr. Matthias Steinmetz, noted: "With the First Light of 4MOST, we are opening a new chapter in sky surveys. 2436 optical fibres allow us to capture thousands of objects in the southern sky simultaneously. 4MOST will help to answer fundamental questions about the formation of the Milky Way, the evolution of galaxies and the forces that shape the Universe."
The first light observations featured the Sculptor Galaxy (NGC 253) and the ancient globular cluster NGC 288. The Sculptor Galaxy, located 11.5 million light years away, is one of the largest galaxies visible from the southern hemisphere and is actively forming new stars. NGC 288, by contrast, is a dense cluster of about 100,000 stars formed some 13.5 billion years ago, near the dawn of the Milky Way's history.
Within just 20 minutes of its first exposure, 4MOST recorded spectra from over 2,000 additional celestial objects, ranging from nearby stars to galaxies as distant as 10 billion light years. These spectra will allow astronomers to measure properties such as temperature, mass, chemical composition, and velocity - offering new insights into cosmic structure and evolution.
The facility's fibre-optic positioning system allows all 2,436 fibres to be moved to new targets in under two minutes. Light collected through the fibres is fed into three spectrographs, each capable of analysing 800 objects simultaneously. Two spectrographs cover the full visible to near-infrared range (370-950 nm), while a third provides high-resolution spectra across specific wavelength bands for precise stellar chemistry studies.
Observation planning is coordinated remotely from the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, while operations are conducted by ESO. Processed data will be sent to the 4MOST Data Centre at the University of Cambridge and then distributed through archives at AIP and ESO for use by the global scientific community.
The 4MOST collaboration involves over 700 researchers from universities and institutes worldwide. In its first five years, it will carry out 25 science programmes exploring topics such as the origin of chemical elements, galactic evolution, dark matter distribution, and dark energy's role in cosmic expansion. Its ability to support multiple programmes simultaneously ensures efficient use of every observing night, delivering an unprecedented view of the dynamic and diverse southern sky.
Related Links
4MOST
Stellar Chemistry, The Universe And All Within It
