Astronomy Light Pollution: A Threat to Astronomy in the Atacama Desert

27 May 2025

The climatic and geographic conditions of the Atacama Desert, with its high altitude and countless cloud-free nights, offer astronomers unique glimpses into the universe. Several major international research projects benefit from these ideal conditions, including telescopes operated by the European Southern Observatory (ESO), such as the prominent Paranal Observatory. But this one-of-a-kind research site is now a risk, with a planned industrial project, named INNA, threatening to significantly increase light pollution and permanently compromise observation conditions. This would also impact the work of Prof. Dr Dominika Wylezalek, who, in March 2025, was appointed Professor of Extragalactic Astrophysics at the Centre for Astronomy of Heidelberg University (ZAH) and Director of the Institute for Astronomical Computing.

Professor Wylezalek, how important is the Atacama Desert for astronomical research, and in what way is the INNA project a threat?

Wylezalek: Anyone who has tried to look at the night sky in a big city knows that, even on clear nights, there’s not much to see. This is due to light pollution, which is caused by streetlights, neon signs and constant road traffic. That’s why modern telescopes are deliberately built in remote areas where artificial light barely interferes with our view of the cosmos. One of these rare places is the Atacama Desert in Chile, one of the world’s most important locations for astronomical research. With its extreme dryness, stable atmosphere, high altitude, and over 300 cloudless nights per year, it is an ideal site for observation – one where the night sky can be observed in ways that are only possible in a few remaining places on Earth. A large-scale industrial project like INNA, however, would dramatically increase light pollution in the region, posing a serious long-term threat to one of the last truly dark places on the planet.
 

How important is the data collected at the Atacama observatories to your research?

Wylezalek: The telescopes operated by the European Southern Observatory – including the Paranal Observatory and the Extremely Large Telescope (ELT) currently under construction – are among the most advanced and powerful observatories in modern astronomy. With a mirror diameter of around 39 meters, the ELT will soon be the largest telescope in the world, setting new standards for how we observe the universe. In cooperation with the Chilean government, ESO has executed some of today’s most ambitious, large-scale scientific projects with the construction and operation of these observatories. The data collected there plays a central role in my own research, as it does for many of my colleagues here in Heidelberg. For example, we study how supermassive black holes influence the development of entire galaxies and can bring star formation to a halt. These kinds of insights would be nearly impossible without the unique observational capabilities provided by ESO.

In early March, you visited the endangered telescope site in Chile as part of a delegation led by German Federal President Frank-Walter Steinmeier. What was your role in that delegation?

Wylezalek: The invitation came as a complete surprise. I just received an email on a Friday afternoon. Honestly, my first thought was: This has to be spam. But once I checked the sender’s address and contact details, it quickly became clear that it was a real invitation. I don’t know exactly how the guest list was compiled at the Federal President’s Office, but it seems that my connection to ESO and astrophysics had something to do with it. Before I moved to Heidelberg five years ago, I spent a total of six years working for the European Southern Observatory – first from 2011 to 2014 as a doctoral candidate, and later from 2017 to 2020 as an independent research fellow. During that time, I spent around 30 to 40 nights at the telescopes in Chile and was involved in commissioning new measuring instruments and observation modes.

Thanks to this hands-on experience, I was able to provide the President and the delegation with technical insights into how the facilities operate and what day-to-day work on-site looks like. Not only that, but in my role as an active researcher and newly appointed professor, I was able to explain concrete scientific projects and current research findings in an accessible way.

In light of the looming INNA project, President Steinmeier’s visit also took on a political dimension. Of course, we’re also hoping for support from the German government. President Steinmeier himself was deeply impressed by the Paranal site, calling it a “magical place”. In his press address, he emphasized the importance of the observatory for scientific cooperation between Chile and Germany. His exact words were: “We are proud that German scientists are part of this cutting-edge research.”

The Chilean government is currently reviewing the plans for the megaproject. Do you still see a chance to stop it?

Wylezalek: For me, it’s not about preventing the project outright. Expanding green energy infrastructure is undoubtedly very important. Instead, the goal should be to find a solution that allows both to coexist. We have established models to calculate light pollution based on the location of such facilities. These clearly show that the impact decreases rapidly with distance. Relocating the INNA project by just 50 to 100 kilometers would significantly reduce its effect on the night sky and, in turn, on the observatories’ operations.

What alternatives would there be for future astronomical projects if the Atacama Desert became unusable? 

Wylezalek: There are a few alternative sites around the world that are also well suited for astronomical observation – such as Mauna Kea in Hawaii or other regions within the Atacama Desert itself. Many major observatories are already located in these areas. However, Paranal and Cerro Armazones – the future site of the Extremely Large Telescope – are unique in many respects and make this region the best location in the world for ground-based astronomy. This would make it much more difficult to find truly equivalent alternatives if conditions were seriously compromised. It would be a considerable loss to science. All the more reason to ensure these conditions are protected for the long term.

Do you see ways to avoid similar conflicts in the future?

Wylezalek: Yes, conflicts of this kind are definitely avoidable – provided that communication between stakeholders starts early and on equal footing. The key is to make planning processes more transparent and take into account relevant scientific, environmental, and cultural factors from the very outset. Particularly in the case of major infrastructure projects in regions deemed sensitive – whether by virtue of their environmental, scientific, or cultural significance – it is important to identify all stakeholders early on and initiate constructive dialogue. In my view, that’s the best way to prevent such conflicts in the future without slowing down essential progress, like the development of green energy.