Industrial Project Threatens Dark Chilean Skies

By: Jan Hattenbach January 14, 2025 6

An industrial megaproject in Chile is threatening the pristine darkness over Paranal, one of the world’s most important observatories.

Update (March 17, 2025):

The European Southern Observatory (ESO) has conducted a new, in-depth analysis of the impact of the AES Andes industrial project on the skies above its observatories in the Paranal area, finding that light pollution would increase by at least 35% above the Very Large Telescope and by more than 50% above the south site of the Cherenkov Telescope Array Observatory. Vibrations from the project could also seriously impair the functioning of the Extremely Large Telescope. Find more details in the ESO press release.

Find the original story, published January 14, 2025, below.

The dark skies above ESO’s Paranal Observatory, home to ESO’s Very Large Telescope (VLT), yield breathtaking views so clear and so full of stars that you could almost touch them. Standing atop a platform at VLT, ESO Photo Ambassador Petr Horálek reaches towards a standout object in the sky. You may assume this bright body, like many others in the sky, to be a star, but it is in fact a planet in our Solar System: the gas giant Jupiter. Closer to Earth, the four Unit Telescopes (UTs) that comprise the VLT can be seen in the background. Each UT features an 8.2-metre mirror and they operate synergistically to produce some of the sharpest views of the Universe. Accompanying the four UTs are four smaller, moveable Auxiliary Telescopes (ATs) which have 1.8-metre mirrors. The Chilean Atacama desert once again proves its value as the ideal location for ESO’s VLT. The remoteness of the observatory means that there is very little to no light pollution, which is vital for astronomy and also yields such breathtaking views. — The dark skies above the European Southern Observatory’s Paranal Observatory, home to the Very Large Telescope, yield breathtaking views so clear and so full of stars that you could almost touch them.
*ESO / P. Horálek*

When a study in 2023 crowned Cerro Paranal the darkest observatory site in the world, astronomers must have felt reassured to have chosen the right spot. The 2,635-meter (8,645-foot) mountain in Chile’s Atacama Desert is home to the European Southern Observatory’s (ESO) Very Large Telescope, one of the most advanced and prolific astronomical facilities.

But now, if a company named AES Andes (a subsidiary of the U.S. power company AES Corporation) gets its way, Paranal’s observational prowess might soon be history: Light pollution emitted by a proposed industrial “megaproject” could do away with the dark skies over this observatory.

“Paranal’s privileged position will disappear,” fears ESO’s director general Xavier Barcons. “We will become a sort of ‘average’ astronomical observatory. This is why we’re worried.”

The bad news comes at a time when ESO is building its “next big thing”: the Extremely Large Telescope, or ELT, just 22 kilometers (14 miles) to the east of Paranal, on another mountain called Cerro Armazones. When completed at the end of the decade, the ELT will be the world’s biggest optical observatory.

Also, just to the southeast of Paranal, an international consortium of 25 countries, including the U.S., Australia, Japan, and most of Europe, is planning to operate the southern site of the Cherenkov Telescope Array (CTA). This observatory would detect high-energy gamma rays by the visible light they generate when they interact with our atmosphere. The telescope would work together with its northern counterpart on the Spanish island on La Palma.

This aerial view shows the relative locations of the Very Large Telescope at Paranal Observatory, the nearby site of the Extremely Large Telescope at Cerro Armazones, and the proposed site for the southern arm of the Cherenkov Telescope Array, all located in Chile's Atacama Desert. The proposed industrial project site is located south of the CTA, just outside the bottom left of the picture. Find an interactive map of INNA's proposed location here.
*ESO / CTAO / M. Kornmesser*

The AES project puts these observatories under threat. According to information ESO has obtained from AES, part of the industrial complex may be built just 5 km from the CTA site and only about 10 km from Paranal and Armazones. “One problem with this [proximity] is the dust generated during the construction, but the biggest issue is light pollution, not only during construction but during operation,” Barcons says.

Not all details of the project, which is called “INNA” (Infraestructura Energética para la Generación de Hidrógeno y Amoníaco Verde), are available to the public. However, the AES submitted the project to the Chilean environmental agency for assessment in December 2024, and the submitted description of the project, which is publicly available, outlines INNA’s purpose and size.

The project is supposed to generate “green” hydrogen and ammonia from sea water by using solar and wind energy inland in the Atacama. Both solar power and wind turbine arrays would produce energy at gigawatt scales (hence the attribute “green”); there would also be production facilities, power lines, pipelines for sea water and processed products, and a port located at the coast for export of the final products. The sheet names a total area required of 11.7 square miles, a lifetime of 42 years, and an investment of $10 billion.

As soon as ESO learned of the plans in August 2024, the organization reached out to AES, Barcons recounts: “We showed them that the impact, based on sophisticated models of light pollution, is going to be very serious on the observatory sites. And we told them that if they moved away to 50 kilometers, according to the simulations, we will be safe.” Nonetheless, AES submitted the original plans to SEA without changes. “They are aware that they’re going to damage us, and they have essentially ignored us.”

While AES did not reply to Sky & Telescope’s questions regarding the possibility of relocating the facilities, the company did respond to dark-sky concerns in an email: “This proposed project specifically incorporates the highest standards in lighting in its design, complying with the Ministry of the Environment’s new regulatory requirements (Decree No. 01/2022), which aim to prevent light pollution.”

Barcons hopes that the Chilean government will help find a solution. After ESO contacted the country’s authorities through the Ministry of Foreign Affairs, a round table including representatives of the ministries of Science, Environment, Energy, and Economy was called. “They’ve had a few meetings and they’re taking this very seriously. But we’re at a point now where the project has been submitted and we’re very concerned that if approved, it might compromise our business and our investments.”

ESO has been developing the Paranal site since the early 1990s, with planning starting even earlier. Its four 8-meter unit telescopes became operational in 2000, so 2025 marks the 25th anniversary of the Very Large Telescope.

Barcons adds that ESO very much supports the production of clean energy. “I don’t see why Chile has to choose between the best astronomical observing sites in the world and green energy production. It can have both — just not in the same place!”

Editorial note (January 15, 2025): The article has been edited to reflect AES's response to request for comment.

Comments

Andrew James

January 15, 2025 at 4:29 pm

Another example of true 'crimes against humanity.' Like Musk's Starlink, the environment suffers, while those greedy corporations profit. They work by using the little chinks, chiselling away at the world, which falls into ruin more and more and day by day. Worse they hide behind legalistic arguments, mainly to the stall and prevaricate or use inauthentic discussions so they can hide the damage that they're actually doing.

As usual, any minority of people are exploited, who have their hands tied, while government and industry do what they please and unfettered by any moral obligation or decency. Already: “They are aware that they’re going to damage us, and they have essentially ignored us.” means we've already lost.

It just stinks.

Note: Historically, hasn't the American government and American corporations already done enough damage in Chile? Copper metal or 1973, for example.