Astronomy crisis: Chile’s cherished night sky threatened by development

• Chile’s Atacama Desert is one of the darkest spots on Earth, a crown jewel for astronomers who come to study the origins of the universe in this inhospitable desert along the Pacific coast.

A rare confluence of factors makes the Atacama an ideal home for some of the world’s biggest ground-based astronomy projects — dry climate, high altitude and, crucially, isolation from the light pollution of civilisation.

“It’s a perfect cocktail for astronomy,” said Daniela González, executive director of the Skies of Chile Foundation, a nonprofit that defends the quality of the country’s night skies.

But that may not be the case for much longer, a group of leading scientists warned in an open letter to Chile’s government released Tuesday.

A private company is moving forward with plans to construct a giant renewable-energy complex in sight of one of Earth’s most productive astronomical facilities — the Paranal Observatory, operated by the international consortium known as the European Southern Observatory, or ESO.

In the letter, 30 renowned international astronomers — including Reinhard Genzel, a 2020 Nobel laureate in astrophysics who conducted much of his prize-winning research on black holes with ESO telescopes in the Atacama — describe the project as “an imminent threat” to humanity’s ability to study the cosmos and unlock more of its unknowns.

“The damage would extend beyond Chile’s borders, affecting a worldwide scientific community that relies on observations made at Paranal to study everything from the formation of planets to the early universe,” the letter reads. “We are convinced that economic development and scientific progress can and must coexist to the benefit of all people in Chile, but not at the irreversible expense of one of Earth’s unique and irreplaceable windows to the universe.”

These scientists join a growing chorus urging the Chilean government to relocate the hydrogen-based fuel plant since the plan was unveiled a year ago by AES Andes, an offshoot of the US-based AES Corp. AES says its technical studies show the project will be compatible with astronomical observations and compliant with Chile’s strict light-pollution regulations.

The proposal calls for 3,000 hectares (7,400 acres) of wind and solar farms, a desalination plant, and a new port. That would mean not only a major rise in light pollution but also new dust, ground vibrations, and increased atmospheric turbulence that blurs stars and makes them twinkle. All of that — just 3 kilometres from Paranal’s powerful telescopes — will interfere with the view of key astronomical targets and could obstruct scientific advances, experts say.

“At the best sites in the world for astronomy, stars don’t twinkle. They are very stable, and even the smallest artificial turbulence would destroy these characteristics,” said Andreas Kaufer, ESO’s director of operations, who estimates the AES project would increase light pollution by 35%.

Although this conflict is specific to Chile — home to 40% of the world’s astronomy infrastructure — it reflects a broader tension between natural darkness and industrialisation. Light pollution makes the night sky about 10% brighter each year.

“Major observatories have been chased out to remote locations, and essentially now they’re chased out to some of the last remaining dark-sky locations on Earth,” said Ruskin Hartley, executive director of DarkSky International. “All of them are now at risk from encroaching development and mining. It’s happening everywhere.”

Associated Press