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Tracing the Big Bang

With the University of Cologne involved, a powerful radio telescope is rising in Chile’s Atacama Desert to probe the origins of the universe

One of the world’s most powerful radio telescopes is being built in the Chilean Atacama Desert with the participation of the University of Cologne. Once assembled, it will be able to look back to the origins of our universe. Its construction in Germany, its assembly at an altitude of 5,600 metres, and the expected scientific results – a journey to the limits of what is possible.

By Jürgen Rees

The sun can sear the skin in minutes, and the air is so deprived of oxygen that breathing becomes more and more difficult with every step. Under these conditions, the engineers and technicians are dependent on additional oxygen and, for safety reasons, are not allowed to exceed their strenuous shift work by even a single minute. Working on the mountain to help build the telescope requires a sense of adventure: for every working day spent at this altitude, one day below 2,700 metres is mandatory, and workers are not permitted to stay on the mountain for more than 13 days at a time. 

The highest construction site in the world is a challenge for humans and machines alike. Even powerful special lorries carrying the individual parts of the telescope, each weighing several tonnes, struggle to reach the 5,600-metre summit of Cerro Chajnantor in Chile, moving at a crawling pace. Some lorries require the assistance of even more powerful excavators to navigate the dusty, stony winding path. 

In the middle of the world’s driest desert, the Atacama Desert in Chile, a gateway to the universe’s past is being created: In January 2025, the telescope – disassembled in its individual parts – began its journey to Chile: the components were carefully transported from the harbour in Wesel to Antwerp, where they were loaded onto a loose freight ship. After six weeks at sea and a week’s wait in the Chilean port of Antofagasta, the journey continued 450 kilometres by lorry to the Atacama Desert, and finally to the summit. This is where the difficult assembly work began, which is slowly approaching its goal. The commissioning of the telescope, the so-called “first light”, is planned for Summer 2026.

The telescope was designed, developed, and built by the CCAT Observatory, Inc., an international consortium including the University of Cologne, Cornell University, the University of Bonn, the Max Planck Institute for Astrophysics, and a Canadian university network. It is financed by the German Research Foundation and private sponsors such as Fred Young, an alumnus of Cornell University.

Seeing the oldest light in the universe

For Dr Ronan Higgins from the University of Cologne’s Institute of Astrophysics, this is an incredible moment that the scientist, originally from Ireland, has been waiting a long time for: “I am particularly pleased to see that the high-tech components of the telescope have survived the long journey from Germany to Chile in one piece and can now be assembled.” As deputy project engineer, Higgins is more familiar with the new high-performance telescope than almost anyone else. In the dry, thin and therefore transparent atmosphere, he and the many other scientists involved in the project hope to find answers to the big questions regarding the origins of our universe.

For example, the researchers want to observe the oldest light in the universe – an almost unimaginable 13.8 billion years old – which they hope will provide crucial information about the Big Bang and the birth of the first stars. But the scientists are not only interested in the past: How do stars and galaxies form today? Can cosmic background radiation be measured and does the telescope provide clues as to how so-called dark matter and dark energy have influenced the expansion of the universe? “One big question, for example, is why the rate of cosmic star formation keeps changing and is currently in decline,” says Professor Dr Dominik Riechers from the Institute of Astrophysics, lead of the German CCAT consortium and a board member of the project. ”If we grasp this development, we could understand how the universe is evolving.”

Why is this research taking place some 12,000 kilometres away from Germany – in Chile of all places? The Atacama Desert is the driest place on earth, with an annual average rainfall of only around one fiftieth of that recorded in Death Valley in the United States – one of the hottest and driest places in the world. The clear, low-water vapour air allows the radiation from space to pass through almost unhindered. “The large field of view of the Fred Young Submillimeter Telescope and the dry atmosphere allow for an unprecedented deep mapping of the sky,” says Riechers.  

Old light is being stretched

The telescope is being realised by the Duisburg-based company CPI Vertex Antennentechnik. Their high-precision telescopes can be found all over the world, including in the Atacama Desert. Sven Kümmel, engineer at CPI Vertex, is also accompanying the final phase of construction on site: “It’s actually a total contradiction: on the one hand we have a high-precision telescope, on the other hand we have dirt, dust, wind, snow, and ice. That is a real challenge.”

The core of the telescope are two six-metre mirrors made of aluminium and carbon fibre. The mirror surface must be as accurate as possible so that it can look far into space with great accuracy. “We are talking about a tolerance of ten microns across each mirror – a human hair has a diameter of around eighty microns,” explains Ronan Higgins. The two wide-angle cameras CHAI and PrimeCam act as the ‘eyes’ of the telescope. They receive radiation in the so-called submillimetre range – light that has been travelling for billions of years. 

What exactly is radio astronomy in the submillimetre range? In astronomy and physics, the term refers to submillimetre waves (also known as terahertz waves) with wavelengths between a few hundred micrometres and one millimetre, which lie in the range between microwaves and infrared. Many objects and processes in the universe that are of great interest, such as star formation, primarily emit radiation in the submillimetre range. That way, astronomers and astrophysicists can study both extremely cold objects – such as the dense clouds of interstellar gas and dust in which new stars form – and very distant objects in the early universe. In the latter case, the expansion of the universe has stretched the light from these distant objects so they are visible in the submillimetre range.

The waves can also penetrate dust clouds that are impenetrable to visible light. This enables the observation of areas of star formation and the investigation of the chemical composition of interstellar gas. Radio waves are therefore one of the few windows through which scientists can explore the entire universe from the ground.

Pushing the boundaries of physics

Of course, space offers an environment that is even more free of water vapour than the summit of Cerro Chajnantor. However, the location is ideal for the astronomy requirements of the FYST, as it is too large to be transported by rocket. Its location thus offers observation conditions that are as close as possible to those in space.

Submillimeter radiation, for example, originates from clouds of dust and molecules surrounding distant black holes and star-rich galaxies. “This is pushing the boundaries of physics,” says astrophysicist Higgins. FYST will be the most powerful telescope in the world for its mapping speed and sensitivity at its wavelength. It will detail star and galaxy formation from the earliest days of ‘cosmic dawn’ shortly after the Big Bang through ‘cosmic noon’, when most of today’s stars were formed, providing insight on cosmic inflation and gravitational waves from the very first moments of the Big Bang. 

Besides the scientists, donor Fred Young is also certain that the effort is worthwhile: “Our world-class submillimetre telescope at, arguably, the best site in the world for its wavelength, will provide the basis for significant research by many astronomers for many years to come.”

In addition to the scientific findings that make the world and the universe a little easier to understand, technologies are emerging that have an impact far beyond astronomy. “After all, Wi-Fi, GPS, and digital cameras are all by-products of astronomical research,” Higgins reminds us. 

Students at the University of Cologne are also benefiting from the development and construction of the high-tech telescope: They build receivers for the submillimetre radiation and help to precisely align the complex mirror. ”It’s this kind of experience that shapes the next generation of researchers,” says Higgins. In the case of world class telescopes, students generally get processed data to work with. In the case of FYST, however, they are involved in the entire process, including operating the telescope, getting and processing the data, and making science.

In the middle of next year, the big moment will arrive: after approximately seven years of construction, the telescope will look deep into space for the first time – just in time for the University of Cologne’s new Cluster of Excellence DYNAVERSE, which heavily relies on the expected new data. It will then have the most sensitive eyes on earth – ready to capture the oldest light in the universe.

DYNAVERSE – The new Cluster of Excellence between the Universities of Cologne and Bonn, Forschungszentrum Jülich, the Max Planck Institute for Radio Astronomy, the German Aerospace Center, and the Heidelberg Institute for Theoretical Studies is being established as a world-class hub of expertise in radio astronomy, lab experiments, simulations, and machine learning / artificial intelligence. The spokesperson is Professor Dr Stefanie Walch-Gassner at the University of Cologne.

The CCAT Consortium (Cerro Chajnantor Atacama Telescope) is responsible for building the instruments used on the Fred Young Submillimeter Telescope (FYST), as well as for observations, data analysis, and publishing the scientific results. 
The FYST will be a 6-meter diameter telescope designed to operate at submillimeter to millimeter wavelengths and located at an exceptional site at 5600 meters (18,400 feet) on Cerro Chajnantor overlooking the ALMA array. The novel optical design of FYST will deliver a high-throughput, wide-field of view telescope capable of mapping the sky very rapidly and efficiently. The high precision surface and superb site will allow routine access to the 350 micron observing window; during the best weather conditions, operations at 200 microns will be possible. The construction phase is expected to lead to first light in 2026.

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