Dark Skies Under Threat: Industrial Project Jeopardizes Premier Astronomy Site in Chile
A newly released report from the European Southern Observatory (ESO) paints a concerning picture for the future of ground-based astronomy in Chile. The report details the potentially devastating impact of a planned industrial megaproject on the unparalleled observing conditions of the Atacama Desert, home to some of the world’s most powerful telescopes. The project, if realized in its current proposed location, threatens to significantly brighten the night skies, hindering scientific advancements and compromising Chile’s strategic position in astronomical research.
The specific site under threat is the Paranal Observatory, a crucial hub for astronomical exploration. Paranal hosts ESO’s Very Large Telescope (VLT), a flagship facility that has revolutionized our understanding of the cosmos. It is also home to the Cherenkov Telescope Array Observatory (CTAO-South), currently under construction and designed to detect high-energy gamma rays from distant cosmic sources.
The ESO report delivers a stark warning: the industrial project, dubbed INNA (Proyecto Integrado de Infraestructura Energética para la Generación de Hidrógeno y Amoníaco Verde), is projected to increase light pollution at the Paranal Observatory by at least 35%. For the CTAO-South, the increase could exceed 50%. This dramatic rise in artificial light would severely hamper scientists’ ability to observe faint celestial objects, probe the mysteries of the universe, and potentially discover Earth-like exoplanets.
The timing of this threat is particularly unfortunate. ESO is also currently constructing the Extremely Large Telescope (ELT), a next-generation observatory that promises to dwarf the VLT in its capabilities. The ELT’s location, chosen 15 years ago, is a mere 15 miles (25 kilometers) from Paranal, making it equally vulnerable to the light pollution emanating from the proposed INNA complex.
Light pollution is a pervasive and growing problem for astronomers worldwide. It is not merely an annoyance for amateur stargazers; it poses a significant challenge to large, well-funded, international observatories. Recent data from NOIRLab’s Globe at Night project reveals an alarming trend: the night sky is brightening at an average rate of 9.6% per year between 2011 and 2022. This escalating light pollution means that fewer and fewer stars are visible, effectively shrinking our window into the cosmos. A location that once offered a view of 250 visible stars could see that number dwindle to just 100 over the same period.
The consequences of increased light pollution are far-reaching. As Itziar de Gregorio-Monsalvo, ESO’s Representative in Chile, aptly puts it, a brighter sky severely limits our ability to detect Earth-like exoplanets, observe faint galaxies at the edge of the observable universe, and even monitor asteroids that pose a potential threat to our planet. Billions of dollars are invested in building the largest and most powerful telescopes, strategically placed in the best astronomical locations on Earth, with the sole purpose of enabling astronomers to see what no one has ever seen before. Light pollution from projects like INNA doesn’t just hinder scientific research; it steals our shared view of the universe.
The ESO report goes beyond light pollution, highlighting other potential disturbances caused by the INNA project. The construction and operation of wind turbines, a key component of the green-energy complex, could increase ground vibrations, potentially disrupting the delicate instruments at Paranal. The turbines could also generate atmospheric turbulence, similar to that found near wind farms, further degrading the quality of astronomical observations. Finally, the project could lead to the contamination of optical surfaces, including the precious mirrors and lenses of the telescopes, with dust.
The report emphasizes that even a small amount of artificial light contamination can have a significant impact. "A 1% artificial light contamination means that above every 100 photons from the natural sky brightness, there is 1 on average which comes from light pollution," the report states. "This cannot be distinguished by another photon coming from a faint object at the edge of the Universe as detected by the most powerful telescope ever built—like the ELT. Every photon counts in astronomical research."
The conclusion of the ESO report is unequivocal: "Detailed analyses… show that the INNA project executed at the currently baselined site will significantly and negatively impact the performance of all ESO’s telescopes at the site, in a way that due to the proximity, could not be mitigated." The report further states that the ground vibrations from the project would likely exceed the limits tolerated by the VLT interferometer and the ELT itself. The wind turbines would introduce atmospheric turbulence, hindering the observatory’s ability to obtain clear images of the sky.
These disturbances, taken together, pose a serious threat to the long-term viability of Paranal as a world-leading astronomical site. They could lead to the loss of key discoveries about the universe and compromise Chile’s strategic advantage in this critical field. De Gregorio-Monsalvo stresses that the only way to safeguard Paranal’s pristine skies and protect astronomy for future generations is to relocate the INNA complex to a more distant location.
Martin Aubé, an expert on sky brightness, adds another layer of complexity to the problem. He points out that light pollution from a project like INNA would be exacerbated by cirrus cloud cover. While cirrus clouds are thin enough not to disrupt ordinary astronomical observations, they would reflect artificial light, effectively amplifying the problem.
The ESO report concludes that if the INNA project is approved in its current location, the value of the telescopes installed or planned by ESO would be substantially decreased. These losses, the report argues, are manyfold and not recoverable worldwide.
Crucially, ESO authorities are not opposed to the INNA project itself. The issue is the proximity of the industrial complex to the Paranal Observatory. Xavier Barcons, the observatory’s director general, emphasizes that Chile should not have to choose between hosting the most powerful astronomical observatories and developing green-energy projects. Both are declared strategic priorities by the country and are fully compatible, provided the facilities are located at sufficient distances from one another.
ESO plans to submit a full technical report on the potential impacts of INNA on Paranal to the relevant authorities this month, with the intention of making it public before April 3. The hope is that all parties involved can reach a mutually beneficial solution, one that allows Chile to pursue its ambitions in clean energy without sacrificing its invaluable contributions to astronomical research. The future of dark skies, and the groundbreaking discoveries they enable, hangs in the balance.
