October 21, 2025, by Anna Walter
Photo: ESO/B. Tafreshi
4MOST is located at the Paranal Observatory in the Atacama Desert in Chile. The inhospitable and difficult-to-reach location is one of the world’s best locations for astronomy. There is virtually no cloud cover, hardly any light pollution or precipitation.
A few days ago, the European Southern Observatory put a new instrument into operation, the 4-meter Multi-Object Spectroscopic Telescope (4MOST), which will carry out unique surveys of the sky over the next five years. The University of Hamburg is involved in this milestone of the international 4MOST consortium with its Cluster of Excellence “Quantum Universe”.
On October 18, 2025, 4MOST captured the light of the night sky for the first time. This moment is crucial in the life of every telescope because it marks the beginning of its scientific work. 4MOST does not just create images of the sky, but also captures detailed information about the color components, so-called spectral colors, for over 2,400 celestial objects. By breaking down light into its individual color components, spectroscopy provides astronomers with information about the properties of celestial bodies, such as their temperature, chemical composition and movement.
4MOST is located at the Paranal Observatory in Chile and is the largest instrument for spectroscopic sky surveys in the Southern Hemisphere. The combination of a large field of view, the number of objects observed at the same time and the large number of spectral colors recorded at the same time is unique in the world. The powerful instrument is capable of simultaneously separating light from 2,400 celestial objects into 18,000 color components. By analyzing the detailed spectral colors of thousands of objects every 10 to 20 minutes, 4MOST creates a comprehensive catalog of physical parameters for approximately 30 million objects distributed throughout the southern sky.
4MOST helps research dark matter
In this way, 4MOST contributes to a better understanding of the formation and evolution processes of stars and planets, the Milky Way and other galaxies and to gain new insights into black holes and exotic objects as well as the universe as a whole. “With the help of 4MOST, we also obtain information about the distribution of dark matter in the universe,” explains Jochen Liske, Professor of Observational Astronomy at the Hamburg Observatory and senior scientist at the Cluster of Excellence “Quantum Universe” at the University of Hamburg. “We are interested in this because the statistical distribution of dark matter in the universe allows us to draw conclusions about the physical properties of the dark matter particles.”
Liske and his team have contributed to the development of the instrument over the last 10 years. The University of Hamburg contributed a total of two million euros to the construction of 4MOST, most of which was used to develop one of the instrument’s three spectrographs. “After the long development period, we are overjoyed that the observations are finally starting,” says Liske happily.
The Cluster of Excellence “Quantum Universe” at the University of Hamburg researches the creation and development of the universe from its origins to the present day. It has long been known from astronomical observations that the gravity of visible matter in the universe, such as stars and gas, is not sufficient to explain their movement in galaxies. Researchers therefore assume that every galaxy is permeated and surrounded by dark matter. “Quantum Universe” is significantly involved in the development and implementation of experiments intended to detect dark matter and thus solve one of the greatest mysteries of the universe.
In its first measurement, 4MOST observed a large section of the sky that contained two prominent objects: the Sculptor Galaxy and the globular cluster NGC288. This image shows 4MOST’s hexagonal field of view and the many objects marked with different colored dots for different object types. 4MOST has captured a spectrum for each of these individual objects so that their properties, such as chemical composition or temperature, can be examined. The figure shows an example of the spectra of two objects.
Bildrechte: AIP/R. de Jong, Lyon Astrophysical Research Center/J.-K. Krogager, Background: Harshwardhan Pathak/Telescope Live
