Chile’s perfect skies for stargazing under threat from giant chemical plant | Chile

In the Atacama desert, the driest non-polar region on Earth, the sky shines when the sun sets.

Up in the arid hills 130km south of the Chilean city of Antofagasta, comets burn brightly and flawless trails of stars and nebula streak the night sky.

So complete is the darkness in this part of the world, that Indigenous peoples staring up at these skies saw past the stars to contemplate dark spots in between – finding the forms of animals and ancestors in the perfect darkness beyond.

These are the darkest, clearest skies for observation in the world, and they have propelled Chile to become the world’s astronomical powerhouse.

But they are under immediate threat, astronomers are warning.

In December, energy company AES Andes put forward plans for the country’s first industrial-scale green hydrogen and ammonia processing plant, known as the Inna project.

The proposed 3,000-hectare facility, which also includes a port, transport links to the coast and three solar power plants, will generate solar and wind energy, feeding excess into the national grid.

The suggested main site is just 11.6km from one of Chile’s most important observatories.

Last Monday, Chile’s environmental regulator criticised the project’s proposed location, but let a deadline to strike down the $10bn project elapse.

The threat to Chile’s observatories remains.

The astronomical community is unequivocal in its rejection of the proposal, saying that the size and scale of the project – which will need to be illuminated at night for safety – as well as light reflected off roofs, solar panels and machinery, will seriously affect readings.

Even the dust kicked up during construction and the atmospheric turbulence of planned wind turbines worry scientists.

“An ideal location for ground-based astronomy requires three things: a large number of clear nights, low atmospheric interference, and dark skies,” said Dr Fabio Falchi.

“If we combine all of these then we have very few places on Earth which are ideal: the very best are Paranal and Armazones.”

The very large telescope (VLT) at Paranal observatory, built 2,600m above sea level, where the dry air stings your lips and the sun scorches the earth, has taken the readings which have won three Nobel prizes.

And on nearby Cerro Armazones, the extremely large telescope (ELT), a hulking mass of steel and concrete like a spaceman’s helmet, is under construction.

When it is completed at the end of the decade, it will be the largest and most powerful telescope ever built, allowing astronomers to see into distant galaxies to identify Earth-like exoplanets which might support life.

Light will be concentrated by a vast mirror comprising 798 polished hexagonal segments, allowing us to see further into space than ever before.

“Essentially, brighter skies lower the quality of the data you can collect,” said Dr Falchi. “Light pollution in the vicinity of the ELT would mean that the readings it can take would effectively be the same as those of a much smaller telescope.”

The Paranal observatory is operated by the European Space Observatory (ESO).

“Our goal is to take a step forward in our understanding of the universe, and to do this, we need the best quality skies possible,” explained Itziar de Gregorio, ESO’s director in Chile.

All of ESO’s astronomical infrastructure is in Chile, and it has operated in the country for more than 60 years.

“To keep observing the universe, we need atmospheric stability and for darkness to prevail – without this, we won’t be able to further our understanding,” said de Gregorio.

“Paranal is a truly exceptional site. If we lose it, we lose one of our last windows into the universe, and Chile will lose its astronomical leadership, and the hundreds of millions of euros invested here. It will become a mediocre site and we will have to look elsewhere for future projects.”

A 60-day public consultation process for the Inna project ends on 3 April.

AES Chile could not be reached for comment, but a press release from December claimed that the company was committed to the “highest environmental standards”, and that its project aligned with Chile’s green hydrogen goals.

“How can we compare the short-termism of an industry which will create jobs and local economic development with this long-term goal of studying and understanding the universe?” asked astronomer Eduardo Unda-Sanzana, who is leading a crusade to protect the skies of northern Chile from the University of Antofagasta.

“It’s a false equivalence: human beings and the knowledge they pursue are worth considerably more than the money that ends up in their pockets each month.”

Chile has pioneering light pollution regulation as part of its environmental norms, setting limits on light emissions in certain areas and promoting dark skies as a basic right.

“It is nonsense to me that with 6,400km of coastline in Chile, they have to put this facility so close to the biggest telescope in the world,” said Dr Falchi.

“We need to face the problem of light pollution in the same way we tackled atmospheric pollutants, where we had huge success putting red lines in place which should not be passed.

“We need to do this in order to save the night sky in the long term.”