A brand new industrial megaproject threatens the prospect of the world's greatest observatories

Astronomers have been grappling with threats to their clear skies on all fronts lately. One of the most notable battles we have repeatedly reported on is against Starlink and other mega-constellations of satellites, which, while providing high-speed internet in the most remote locations, also disrupt observations by sensitive telescopes due to their reflectivity and rapid movement speed. They also represent a global problem, while a more down-to-earth problem arises at a very particular observatory. A huge industrial facility threatens the European Southern Observatory's Paranal telescope, which is planned just a few kilometers from the site.

ESO recently released a statement calling on the government of Chile, where Paranal is located, to consider moving the project elsewhere. Currently, AES Andes, a subsidiary of AES Corporation, an American energy utility, recently submitted a proposal for the environmental assessment of a 3000-hectare industrial area that includes hydrogen and ammonium factories, power generation machines and, more importantly, many other lights.

Lights are an essential part of any large industrial project, but they pose a particular threat to the Paranal. A recent study found it to be the observation site with the least amount of light pollution. Any significant increase in this baseline above just about 0.1% of the general background level could have a massive negative impact on the capabilities of the telescope located there.

Levels of light pollution at observatories around the world.
Image credit – ESO, modified from Falchi et al

This telescope has been an integral part of the astronomical community, contributing to research such as the 2020 Nobel Prize-winning studies of Sgr A*, the supermassive black hole at the center of our galaxy. It also represents billions in investment by the member states of the European Southern Observatory.

When you think of natural resources, you might not think of clear skies, but for Chile you do. In addition to Paranal, two other Chilean observatories are among the three major astronomical observatories with the least light pollution: Armazones and Tokyo Atacama. In addition, it has four others in the top 15, making it one of the best contributors in the world to this type of astronomy.

This contribution is intended to grow with ESO's ongoing development of the Extremely Large Telescope not far from the Paranal site. While the light pollution from the proposed industrial facility may not extend as far as what will be the largest telescope of its kind in the world, a precedent by the Chilean government to approve projects that would undermine the investments of ESO and other astronomical institutions would be detrimental long-term perspective of observations in the country.

The night sky over Paranal.
Image credit – ESO YouTube channel

Since the AES Andes proposal is still in the environmental impact assessment phase, it is still early enough to provide feedback for a possible alternative. ESO's letter shows that it supports the project conceptually, but suggests moving it to another location so as not to negatively impact the telescope. Whether this is feasible and whether the Chilean government will even support it remains to be seen. But this threat to one of the world's largest observatories should not be ignored.

Learn more:
ESO – The world's darkest and clearest skies are at risk from a mega industrial project
UT – ESO releases the most detailed infrared map of our galaxy ever created
UT – Existing telescopes could directly observe “ExoEarths…” with a few adjustments
UT – The Paranal and the Shadow of the Earth

Mission statement:
Touching the Arc of Space – taken at Paranal Observatory.
Photo credit – ESO / P. Horálek

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