On October 18, 2025, the 4-meter Multi-Object Spectroscopic Telescope (4MOST) achieved a significant milestone by capturing its first light at the European Southern Observatory’s (ESO) Paranal Observatory in Chile. This moment marks the beginning of its scientific operations, allowing astronomers to embark on extensive studies of the universe.
The 4MOST is not designed merely to take images; it records spectra of celestial bodies, breaking down their light into individual colors. This capability enables the telescope to analyze the light from up to 2,400 celestial objects simultaneously, dissecting it into 18,000 color components. Such detailed spectral data will allow researchers to investigate the chemical compositions and physical properties of stars, planets, and galaxies.
Unraveling Cosmic Mysteries
Once fully operational, 4MOST will focus on various astronomical phenomena, including the formation and evolution of stars and planets, the structure of the Milky Way and other galaxies, as well as the study of black holes and dark matter. The telescope aims to compile a comprehensive catalogue of temperatures, chemical compositions, velocities, and other parameters of tens of millions of objects across the southern sky.
As the largest multi-object spectroscopic survey facility in the southern hemisphere, 4MOST stands out for its combination of a wide field of view and its ability to observe numerous objects simultaneously. The project commenced in 2010, with plans for the facility to operate for at least the next 15 years.
Leading the initiative is the Leibniz Institute for Astrophysics Potsdam (AIP), which has played a crucial role in the telescope’s development. Notable contributions from AIP include the wide field camera with six lenses, its guiding and focusing system, and an intricate fiber system made up of over 2,400 glass fibers, each comparable in diameter to a human hair. AIP also oversees the operational planning and data management of 4MOST.
Excitement from the Team
The significance of this achievement was highlighted by Roelof de Jong, Principal Investigator and Milky Way section head at AIP, who stated, “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.” He emphasized the remarkable capability of capturing light that has traveled for billions of years.
Joar Brynnel, Project Manager, expressed his enthusiasm for the milestone, stating, “Reaching this milestone is a wonderful achievement after more than a decade of intensive efforts. It is hard to put into words the excitement of realizing that the facility not only meets, but even exceeds the required performance.”
The first observations included significant cosmic structures, such as the NGC 253, also known as the Sculptor or Silver Coin galaxy. It is one of the largest galaxies in the southern sky and is approximately 11.5 million light-years away. The 4MOST observations also captured a super star cluster, various types of stars, and gas emissions from newly formed stars within this galaxy.
Another notable object observed was the Globular Cluster NGC 288, a dense group of around 100,000 ancient stars located about 30,000 light-years from Earth. This cluster is believed to have formed approximately 13.5 billion years ago during the early phases of the Milky Way’s formation.
In just 20 minutes of its first science observation, 4MOST gathered spectra from over 2,000 celestial objects, enabling scientists to extract vital information about their characteristics, such as temperature, age, and evolutionary stage. The telescope also observed a pair of overlapping galaxies located 900 million light-years away, along with many other galaxies extending up to 10 billion light-years.
The 4MOST science team comprises more than 700 researchers from institutions worldwide. Over its first five years, the telescope will conduct 25 different science programs, with both consortium members and external astronomers contributing to the research agenda. The multi-fiber design of 4MOST permits simultaneous observations of different scientific projects, enhancing its efficiency.
Highlighted research areas include the origins of chemical elements, the evolution of the Milky Way, and the formation of galaxies and black holes. Researchers will also explore the properties of dark matter and the nature of dark energy, which drives the universe’s expansion.
At the core of its operations, 4MOST employs 2,436 optical fibers that transport light to three spectrographs, each capable of observing 800 objects simultaneously. This system facilitates the detailed analysis of light across a broad spectrum—from ultraviolet to infrared—enabling precise measurements of various astronomical phenomena.
Planning observations is conducted remotely from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. As conditions permit, the telescope adapts its observations to capture optimal data. The European Southern Observatory is responsible for executing observations, while data is analyzed at the University of Cambridge before being archived and made available to the scientific community.
The successful capture of first light by the 4MOST telescope marks the start of a new era in astronomical research, promising to answer some of the most profound questions about the universe. As researchers eagerly await the insights that will emerge from this powerful facility, the journey of exploration has only just begun.
