The renowned Paranal Observatory, home to the European Southern Observatory’s (ESO) Very Large Telescope (VLT), faces a significant threat to its exceptionally clear night skies. A proposed industrial complex by AES Andes, a subsidiary of a U.S. power company, could drastically impact astronomical observations at this crucial research site in Chile’s Atacama Desert.
The VLT, a complex of four 8.2-meter telescopes and four auxiliary 1.8-meter telescopes, produces remarkably sharp images of the universe. Observatory officials are deeply concerned about the potential for the proposed project to diminish the VLT’s capabilities and permanently alter the night sky visibility in one of the world’s premier locations for astronomical research.
The Inna Project and Its Potential Impact
The proposed project, named Inna, is a large-scale green hydrogen initiative. Spanning over 7,413 acres, it would include a port, hydrogen and ammonia production plants, and thousands of electric generators. The proposed site is worryingly close to Paranal, situated a mere 3 to 7 miles (5 to 11 kilometers) from the telescopes. AES Andes submitted an Environmental Impact Assessment to Chilean authorities in late 2024, emphasizing their commitment to local economic development and environmental standards in a company statement.
However, the potential environmental impact is precisely what concerns the ESO. The Atacama Desert boasts some of the darkest and clearest skies on Earth. Low atmospheric moisture minimizes light absorption, and the high altitude reduces atmospheric turbulence, creating ideal conditions for astronomical observation.
A graph illustrating how dark skies are above Paranal compared to other observatories.Paranal Observatory’s dark skies compared to other observatories. Graphic: Falchi et al. 2023
Paranal’s Astronomical Significance
From its location in the Atacama, the VLT has captured groundbreaking images of astronomical events, both near and far. In 2021, it imaged 42 of the largest asteroids in our solar system. In 2023, it provided crucial imagery of the aftermath of NASA’s DART mission, which tested asteroid deflection technology. The VLT also detected potential gas clouds from the first stars and captured the first detailed image of a star beyond our galaxy.
The Atacama Desert hosts numerous existing and planned telescopes, including the Rubin Observatory with its massive LSST Camera, and the Giant Magellan Telescope under construction at Las Campanas Observatory. The LSST Camera is anticipated to see first light later this year, adding to the excitement surrounding astronomy in 2025.
Preserving a Global Treasure
“Chile, and Paranal in particular, is an exceptional location for astronomy,” stated Itziar de Gregorio, ESO’s Representative in Chile, in an observatory release. “Its dark skies are a natural heritage that benefits all of humanity. It’s vital to consider alternative locations for this megaproject to protect this invaluable astronomical treasure.” A 2022 study found that Paranal’s light pollution was significantly lower than at 27 other major observatories, highlighting the site’s unique value.
The Growing Threat of Light Pollution
ESO Director General Xavier Barcons expressed serious concerns about the AES Andes project. “The proximity of this industrial megaproject to Paranal poses a critical threat to some of the planet’s most pristine night skies,” he stated in the observatory release. “Dust from construction, increased atmospheric turbulence, and especially light pollution would irreversibly damage the observational capabilities that have attracted billions of Euros in investment from ESO Member States.”
Hong Kong at night.Light pollution in a city. Photo: Lam Yik Fei (Getty Images)
Ground-based infrastructure isn’t the only concern for astronomers. The increasing number of satellites in Earth’s orbit, particularly megaconstellations like SpaceX’s Starlink, create streaks in astronomical images. These satellite swarms even affect space-based telescopes like Hubble. While mitigation techniques exist, they add complexity to astronomical observations. A 2023 study based on NOIRLab’s Globe at Night project found that the night sky has brightened by 9.6% annually, making some dimmer stars invisible.
The Future of Astronomy at Risk
The VLT will eventually be superseded by the Extremely Large Telescope (ELT), a 39-meter telescope poised to become the world’s largest visible and infrared light telescope. Slated for first light by the end of this decade, the ELT, situated near the VLT at Cerro Armazones, will collect vastly more light than the human eye, enabling detailed studies of exoplanets, black holes, galaxy evolution, and the early universe.
The 2022 study on observatory sky darkness warned, “Astronomical observatories serve as a crucial indicator of the broader issue of light pollution. If we cannot preserve these pristine skies, addressing global light pollution will become an insurmountable challenge.” The study also highlighted the negative consequences of light pollution beyond astronomy, including disruption of circadian rhythms and other adverse effects on Earth’s biodiversity.
The ESO advocates for relocating the AES Andes project, asserting that it’s the only way to prevent irreparable damage to Paranal’s unique skies. The company awaits the Chilean authorities’ decision regarding the project’s environmental impact. There is a certain irony in the possibility of a green energy project jeopardizing the clear skies essential for astronomical research, undermining the very principles of environmental preservation it aims to uphold.
