A powerful new telescope has captured its first glimpse of the cosmos, and could transform our understanding of how stars, galaxies and black holes evolve.
The 4MOST (4-metre Multi-Object Spectroscopic Telescope), mounted on the European Southern Observatory's VISTA telescope in Chile, achieved its 'first light' on 18 October 2025: a milestone marking the start of its scientific mission.
Unlike a typical telescope that takes pictures of the sky, 4MOST records spectra - the detailed colours of light from celestial objects - revealing their temperature, motion and chemical makeup. Using 2,436 optical fibres, each thinner than a human hair, the telescope can study thousands of stars and galaxies at once, splitting their light into 18,000 distinct colour components.
"This is an outstanding feat made possible by an amazing development team," said Dr Roelof de Jong, Principal Investigator of 4MOST at the Leibniz Institute for Astrophysics Potsdam (AIP), which leads the international project. "The first data already look fantastic. To catch light that's travelled for billions of years in a fibre the size of a hair is mind-boggling."
When fully operational, 4MOST will scan the entire southern sky every few minutes, building a catalogue of tens of millions of objects. The data it gathers will help answer fundamental questions about how the Milky Way formed, how galaxies grow, and the mysterious forces of dark matter and dark energy shaping the universe.
The telescope's first images targeted two specific regions: the Sculptor Galaxy, a star-forming spiral 11.5 million light years away, and Globular Cluster NGC 288, a dense sphere of 100,000 ancient stars on the Milky Way's edge. The observations demonstrated 4MOST's ability to capture a wide range of celestial objects in a single shot.
"With first light, we're opening a new chapter in sky surveys," said Professor Matthias Steinmetz, Scientific Director at AIP. "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 project has been more than a decade in the making, involving 30 universities and research institutes - including the University of Cambridge - across Europe and Australia.
Engineers have equipped the VISTA telescope with a new optical camera nearly a metre wide, giving 4MOST one of the largest fields of view in the world for a telescope of its kind. Every 10 to 20 minutes, its fibres can reposition to observe a new set of targets, with a precision that allows it to switch focus across the sky in under two minutes.
Light captured from each fibre travels to a set of three spectrographs that separate it into red, green and blue components, then into finer detail using detectors with a total of 36 megapixels. Two of these spectrographs analyse the full visible and infrared spectrum, while a third focuses on specific colour bands to reveal the chemical fingerprints of stars.
Behind the telescope is an international team of more than 700 scientists working across 25 major science programmes. Some will focus on rare or exotic celestial objects, while others will build large statistical surveys of stars and galaxies.
Planning of nightly observations will be coordinated from the Max Planck Institute for Extraterrestrial Physics in Germany. The European Southern Observatory will operate the system from its Chilean base.
Data from the telescope will be transferred to the University of Cambridge, where researchers at the Institute of Astronomy lead data management. The Cambridge team will extract physical information from the raw spectra before transferring to AIP and ESO, who will distribute the processed results for use by the global astronomy community.
"The 4MOST instrument, with its huge number of optical fibres, has meant the development of a highly sophisticated, high throughput, data flow system, running in Cambridge," said Dr Nicholas Walton, 4MOST Data Management lead. "Our advanced pipeline delivers the highest quality science data, underpinning the amazing discoveries that 4MOST will enable."
"This is such an exciting time to be an astronomer, as 4MOST and other next-generation telescopes come online," said Dr Lisa Kelsey from Cambridge's Institute of Astronomy, a member of the 4MOST team. "It's taken a long time and a huge team to get here, but we can't wait to get to work on some exciting new science."
Kelsey and her Cambridge colleagues are members of one of the first major research projects to use 4MOST: the Time Domain Extragalactic Survey (TiDES). TiDES will focus on extragalactic transients: brief, dramatic events such as supernova explosions, gamma-ray bursts and stars being torn apart by black holes in distant galaxies. By capturing these fleeting flashes of light as they happen, TiDES will help astronomers understand how stars die, how black holes feed, and how the universe evolves on its most violent timescales.
Over its planned 15-year lifetime, 4MOST is expected to revolutionise astrophysical research. By combining an enormous field of view with the ability to study thousands of objects simultaneously, it will deliver one of the most ambitious spectroscopic surveys ever undertaken.
