A green energy plant expected to be built in Chile’s Atacama Desert could increase night-time sky brightness at one of the world’s most valuable astronomical locations by up to 35%, a new study has revealed.
Such an increase would seriously affect the scientific observations conducted by some of the world’s largest and most expensive telescopes, hampering scientific progress in our understanding of the most intriguing phenomena in the universe.
The astronomical site in peril is Mount Paranal, where the European Southern Observatory’s (ESO) Very Large Telescope (VLT) is located. A 7,400-acre (3,000-hectare) green hydrogen production facility, dubbed INNA, has been proposed by U.S. company AES Energy, which submitted an environmental impact assessment to the Chilean Environmental Impact Agency in late December. While an AES Energy spokesperson previously told Space.com earlier that the project will cause a “maximum increase over the natural sky brightness” over Paranal by a negligible 0.27%, ESO’s experts foresee a much more significant impact.
A new study released by ESO on Monday (March 17) calculates that the night sky above VLT could brighten up by up to 35%, as the telescope is located less than 7 miles (11 kilometers) from the prospective INNA site. That’s a staggering increase that would seriously hamper the telescope’s ability to view exoplanets, study the most distant galaxies and detect approaching asteroids.
“The light-pollution figures we are reporting assume that the project will install the most modern available luminaries in a way that minimizes light pollution,” Andreas Kaufer, ESO’s Director of Operations and the lead author of the study, said in a statement accompanying ESO’s new study.
“However, we are concerned that the inventory of light sources planned by AES is not complete and fit for purpose. In that case, our already alarming results would underestimate the potential impact of the INNA project on the Paranal sky brightness.”
VLT, an interferometer consisting of four 28-foot-wide (8.5 m) telescopes that work together as one, is one of the world’s most powerful astronomical instruments. It captured the first ever image of an exoplanet and tracked stars near the black hole at the center of the Milky Way galaxy, among other accomplishments.
The telescope, apart from its size, benefits from the exceptionally dark sky above Mount Paranal, which is the least light-polluted among all major astronomical locations in the western world. The construction of INNA would seriously reduce VLT’s scientific reach.
“We build the largest and most powerful telescopes, in the best place on Earth for astronomy, to enable astronomers worldwide to see what no one has ever seen before,” Itziar de Gregorio-Monsalvo, ESO’s Representative in Chile, said in the statement. “Light pollution from projects like INNA doesn’t just hinder research, it steals our shared view of the universe.”
It’s not just the VLT that will suffer. The Cherenkov Telescope Array Observatory, currently being built at Paranal, will suffer a 50% light pollution increase due to INNA, as it is located barely 3 miles (5 km) from the planned hydrogen plant.
The project will also affect the Extremely Large Telescope (ELT), a visible light mega-telescope with a nearly 125-foot-wide (38 m) mirror, which will be the largest in the world once completed toward the end of this decade. The ESO study estimates that the sky above the ELT could brighten up by 5%, which is enough to affect the demanding observations it is being built to perform.
ESO conducted the study in cooperation with Canadian light pollution expert Martin Aubé using cutting-edge light pollution models. The team used publicly available data from the INNA environmental impact assessment submitted by AES. The company estimates that the complex will require over 1,000 artificial lights.
AES spokesperson told Space.com earlier that the project will comply with “the highest standards in lighting in its design” as required by regulations laid down by Chile’s Ministry of the Environment to prevent light pollution, and protect the astronomical quality of the night skies, the health of people, and biodiversity.
Aside from light pollution, there are other impacts the observatories can expect to experience. The ESO study also found that wind turbines at INNA will stir the thin and quiet atmosphere above the Atacama Desert. The resulting turbulence in the air will further affect astronomical observations, causing a twinkling effect in distant deep space objects as seen from Earth. ESO estimates that observing conditions might worsen by up to 40% because of the turbines.
“Taken together, these disturbances seriously threaten the current and long-term viability of Paranal as a world-leader in astronomy, causing the loss of key discoveries about the universe and compromising Chile’s strategic advantage in this area,” says de Gregorio-Monsalvo, ESO’s representative in Chile. “The only way to save Paranal’s pristine skies and protect astronomy for future generations is to relocate the INNA complex.”
ESO will submit the report to the Chilean authorities as part of the Citizen Participation Process in response to the INNNA environmental assessment.
Light pollution is a major problem affecting astronomical observatories all over the world. The Paranal site is one of the few remaining in the world where light pollution so far remains negligible. The pristine night sky combined with the dryness of the Atacama air provide the best conditions for astronomical study in the whole world.
