The European Southern Observatory is at risk of losing clear skies over its Paranal Observatory in Chile’s Atacama Desert, officials said, due to a proposed industrial complex proposed by a subsidiary of a U.S. energy company.
The Paranal Observatory is home to ESO’s Very Large Telescope (VLT), which consists of four telescopes, each with a 27-foot (8.2-meter) mirror, and four auxiliary telescopes with 6-foot (1.8-meter) mirrors. Working together, the telescopes provide some of the clearest images of the Universe. Observatory staff are seriously concerned that the proposed industrial project could lead to a reduction in what Paranal can see and permanent changes in nighttime visibility in one of the best areas of the sky for astronomical research.
Right next door
The project, dubbed Inna, is a proposed industrial green hydrogen project. The project would occupy more than 7,413 acres of the Atacama River and would include a port, ammonia and hydrogen production plants, and thousands of power generators.
All of this would have to be built from scratch, and the proposed project site would be located between 3 and 7 miles (5 and 11 kilometers) from the Paranal telescopes. Late last month, AES Andes submitted an environmental impact assessment to the Chilean authorities.
“As with any project, our partnership with local communities and stakeholders is a top priority, ensuring that we support local economic development while maintaining the highest environmental and safety standards,” said Javier Deeb, AES’ business leader for the Chilean market, in a statement announcing the application.
The environmental impact is exactly what the European Southern Observatory is concerned about. The Atacama Desert has one of the darkest and clearest skies on Earth. There is little moisture in the air, minimizing the amount of light absorbed by water in the atmosphere, and it is at high altitude, reducing the amount of wobble that terrestrial astronomers typically have to deal with when visualizing distant sources through the atmosphere.
Paranal’s unique location and impact
From its location in Atacama, Chile, the Very Large Telescope captures ancient and recent astronomical events both in our galaxy and far beyond. In 2021, the telescope captured images of 42 of the largest asteroids in the solar system. It continued the trend of space rocks in 2023, when two teams released telescope-derived images of the aftermath of NASA ‘s DART mission, which tested the viability of changing the orbit of a natural body in space. That same year, the telescope spotted gas clouds that may have formed after the first stars, and just two months ago, another team used the telescope to take the first detailed image of a star outside our galaxy.
Due to Atacama’s natural predisposition to astronomy, it is home to many existing and planned telescopes, including Paranal, the Rubin Observatory (which houses the world’s largest digital camera), and the giant Magellan Telescope at Las Campanas Observatory, which is currently under construction. The LSST camera at Rubin Observatory will receive its first light later this year, an event to look forward to during a year full of astronomical events.
“Chile, and Paranal in particular, is a truly special place for astronomy – its dark skies are a natural heritage that transcends the country and benefits all of humanity,” said Icíar de Gregorio, ESO representative in Chile, in a press release from the observatory. “It is imperative that we consider alternative locations for this mega-project that do not jeopardize one of the world’s most important astronomical treasures.”
In 2022, a team of researchers found that light pollution over Paranal was significantly less than over 27 other major observatories. This study showed that in two-thirds of all the large observatories the team studied, light pollution had already increased by 10% compared to the expected natural level, indicating that light pollution is already seriously affecting astronomical observations.
“The results obtained from this work are perhaps the last call for serious, collective, unequivocal and uncompromising action to reduce light pollution, whether it is generated by artificial light or sunlight reflected by artificial objects in orbit,” the research team wrote. “Failure to act will mean a progressive decline in our ability to explore our universe.”
Astronomy under threat
“The proximity of the AES Andes industrial megaproject to Paranal poses a critical risk to the clearest night sky on the planet,” ESO Director General Xavier Barcons said in a press release. “Dust emissions during construction, increased atmospheric turbulence, and especially light pollution will irreparably affect the astronomical observing capabilities that have attracted multi-billion dollar investments from ESO member governments to date.
“Infrastructure on the ground is not the only concern for astronomers. The Earth’s orbit is crowded with satellites that make it difficult to visualize the night sky. Megastellar constellations, including SpaceX’s Starlink, create streaks in astronomical images as individual spacecraft fly across the night sky. Such swarms of satellites even interfere with space telescopes, as seen in some images from the Hubble Space Telescope. There are tricks to cleaning astronomical images from these streaks, but they are nonetheless a problem.
According to recent research, light pollution is getting worse. In 2023, a team of researchers analyzed more than 50,000 observations made around the world between 2011 and 2022 as part of the NOIRLab’s Globe at Night project. The researchers found that the night sky was getting 9.6% brighter every year, causing some dim stars to disappear completely from the sky for some stargazers.
The impact of light pollution on Atacama and astronomy
Eventually the Very Large Telescope will be replaced by the Extremely Large Telescope (I know these are fancy names), which will be 128 feet (39 meters) in diameter and will be the largest visible and infrared telescope in the world. The extra-large telescope will collect 100 million times more light than the human eye and will reveal details of distant exoplanets, black holes, the evolution of galaxies, and the early days of the Universe. The telescope will be located near the VLT, in Cerro Armazones, and its first light is expected in 2028 – although the ESO website offers a more cautious date of “the end of this decade”.
“Astronomical observatories can be seen as the proverbial canary in the coal mine,” the team that assessed the relative darkness of the sky above the observatories wrote in their 2022 paper. “If we can’t even save the life of a canary, we can forget about being able to solve the problem of light pollution as a global environmental problem.” In addition, the group noted that other negative impacts of light pollution will persist, including disruption of circadian rhythms and other negative effects on the health of the Earth’s biodiversity.
In its release, the ESO advocated for the relocation of the AES Andes project, stating that moving the industrial complex “remains the only effective way to prevent irreversible damage to the unique skies of Paranal.” In the meantime, the company is awaiting a response from the Chilean authorities on whether the project’s environmental impact is sufficiently minimal to allow it to proceed as proposed.
The cornerstone of the company’s message is to decarbonize its energy matrix and increase the amount of energy coming from renewable sources. The Chilean authorities would find it painfully ironic that a green energy project continues to develop at the expense of clear skies for astronomers.
