Threat to Astronomy: Industrial Project May Brighten Skies in Chile’s Atacama Desert

A recent report by the European Southern Observatory (ESO) reveals that a planned industrial megaproject in Chile’s Atacama Desert may significantly increase light pollution, jeopardizing the region’s exceptional conditions for ground-based astronomy. The project, known as INNA (Proyecto Integrado de Infraestructura Energética para la Generación de Hidrógeno y Amoníaco Verde), could impact the Paranal Observatory, home to ESO’s Very Large Telescope (VLT) and the Cherenkov Telescope Array Observatory (CTAO-South).

Impact on Observatories

The report highlights that light pollution at the respective telescopes would increase by at least 35% and more than 50%, hindering scientists’ abilities to observe and understand the universe. The technical summary of the team’s report can be accessed here. The CTAO-South is currently under construction, as is ESO’s Extremely Large Telescope (ELT), the successor to VLT, which was chosen for its location about 15 miles (25 kilometers) from Paranal 15 years ago.

The Proposed Industrial Complex

The proposed INNA project is an integrated infrastructure project for the generation of green hydrogen and ammonia. However, its proximity to the Paranal Observatory poses a significant threat to the region’s dark skies. Light pollution is a major concern for ground-based observatories, not just for amateur astronomers but also for large, heavily invested, and multinational observatories.

The Effects of Light Pollution

Data from NOIRLab’s Globe at Night project revealed that the night sky got 9.6% brighter each year from 2011 to 2022, on average. This means that a location with 250 visible stars would see that number reduce to 100 visible stars over the same period. According to Itziar de Gregorio-Monsalvo, ESO’s Representative in Chile, "With a brighter sky, we severely limit our ability to directly detect Earth-like exoplanets, observe faint galaxies, and even monitor asteroids that could cause damage to our planet."

The Consequences of INNA

The report stresses that the INNA project could impact the night sky with artificial light contamination, increase ground vibrations due to the installation of wind turbines, increase atmospheric turbulence due to the operation of those same wind turbines, and contaminate optical surfaces, including telescope mirrors and lenses, with dust. 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, which cannot be distinguished by another photon coming from a faint object at the edge of the Universe.

Mitigation and Relocation

The report concluded 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. The only way to save Paranal’s pristine skies and protect astronomy for future generations is to relocate the INNA complex. The ESO authorities are not opposed to the INNA project itself, but rather the proximity of the project to the observatory.

Finding a Mutually Beneficial Solution

A full technical report on the potential impacts of INNA on Paranal will be submitted to authorities this month and made public before April 3. The ESO hopes that the parties can come to a mutually beneficial decision, one that doesn’t put ambitions of clean energy projects at odds with astronomical observations. As Xavier Barcons, the observatory’s director general, stated, "For us, Chile should not have to make a choice between hosting the most powerful astronomical observatories and developing green-energy projects. Both are declared strategic priorities by the country and are fully compatible—if the different facilities are located at sufficient distances from one another."