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A few days ago, a new regulation on the subject came into effect, but astronomers are calling for a step further: in addition to regulating projects and lighting fixtures separately, they want to ensure the quality of the sky in certain areas, viewing it as a whole. This way, high-interest zones can be preserved with less than 1% light pollution.

Note published in El Mercurio.

A unique wealth in the world could be at risk in northern Chile. Its pristine skies, home to the world’s leading observatories, could be threatened by its worst enemy: light pollution.

On October 19, a new law regulating light pollution primarily in cities came into effect in Chile, which, among other measures, establishes limits on brightness, operating hours for advertising screens and sports venue lights, and promotes the use of warm light.

While there was already a regulation in regions related to astronomy (Antofagasta, Atacama, and Coquimbo), this is now extended to the entire country and also addresses the protection of biodiversity and human health. Additionally, in areas considered to be of Special Protection, such as those mentioned, the regulation is more stringent and took effect immediately.

However, for astronomers, this is just a first step — which is well received — but they are calling for a solution that further protects the skies of places where the highest level of astronomy in the world is developed.

For them, as important as controlling lights in cities and industrial projects is the need to protect the quality of the skies from accumulated light pollution. Ultimately, what they want is for the sky in areas of astronomical interest to be protected with a minimum pollution threshold, for example, that it does not exceed 1%. This is based on the idea that cities and industrial projects that may comply with the regulation separately could have a cumulative effect in areas close to telescopes.

Astronomer Eduardo Unda-Sanzana, director of the Astronomy Center at the University of Antofagasta, says that Chile will concentrate more than 50% of the world’s astronomical capacity by 2030. “And if we only consider the Antofagasta Region — where Paranal, ALMA, and soon the ELT, the largest telescope in the world, are located — it will alone concentrate almost 40% of the world’s astronomical capacity (…). The responsibility and opportunities we have on our shoulders are enormous,” he adds.

But he warns: “Since 1990, we have seen that light pollution in our region has been increasing (…). Cities have grown, and many mining companies have emerged, accompanied by photovoltaic projects.”

He shows a map where light pollution from industrial operations can be seen 30 or 70 kilometers away and from cities like Calama, 300 km away. In the regulation that is already in effect, cities within 100 km of a scientific interest area are regulated more rigorously. “This is not a local phenomenon; it covers large distances, so we need to have a broad view of the effects of our actions,” he says.

“Why, if we are a European organization, do we have all our telescopes in Chile?” asks astronomer Itziar de Gregorio-Monsalvo, head of the Science Office at the European Southern Observatory (ESO) and its deputy representative in Chile. She answers: “Only because of the exceptional conditions of the Atacama Desert (…). This is achieved in very few places in the world, especially at the Paranal Observatory.”

“This is a unique place in the world. There is no better place for astronomical observation,” says Luis Chavarría, ESO representative in Chile, from Paranal. “The atmospheric stability, an ambient humidity that does not exceed 5%, with clear skies for most of the year and less than 1% light pollution,” he adds.

But there is concern. “Around the area granted to ESO for building telescopes, there are sources of light pollution. Some come from the city of Antofagasta, others from mining operations, but more and more new projects related to energy and mining are starting to encroach,” says De Gregorio-Monsalvo.

Another concern she has is that “industrial projects can be established on the edge of our protection area,” she adds.

“In the world, light pollution is advancing at a rate of almost 10% per year, and more than 80% of people live under polluted skies,” says Juan Pablo Valenzano, project coordinator at the Cielos de Chile Foundation, an NGO whose goal is “to promote, protect, and preserve the skies of Chile,” he adds.

For him, light pollution is defined as “all that excess artificial light that is wasted.” This includes fixtures that do not point to the area that needs to be illuminated, those that are on when not needed, or those that emit light in the spectrum that is not visible to the human eye, among others.

Its repercussions, Valenzano says, go beyond astronomy: “It relates to the loss of biodiversity, as it alters the life patterns of nocturnal species, whether in their migration, reproduction, or feeding habits.” It also relates to climate change, as there is an energy waste that contributes to global warming.

The new regulation, Valenzano says, has simple rules, but they do have an impact. “In three regions, Coquimbo, Atacama, and Antofagasta, protected areas have been established due to their astronomical interest: 29 of their 33 communes are designated as special protection areas,” he adds.

The website of the Ministry of the Environment states that the update to the Light Norm recognizes Astronomical Areas as Special Protection Areas, in which the highest emission spectrum requirements (restriction on blue light) will apply.

Valenzano mentions that nearby communes (within 100 km) of astronomical areas have 5 years, until 2029, to change their lighting fixtures to less polluting ones, with warm lights that focus their light downward. However, new projects should already consider this new legislation.

“The regulation that has just come out is a very good step because it is designed to protect observatories from light pollution from cities, from places located 50 or 100 kilometers away,” says Chavarría.

“But what should follow is a sky quality standard that regulates large projects that want to be established near observatories, to ensure that light pollution near the observatories does not increase,” Chavarría says.

This is because, while a project may comply with the regulation, several nearby projects, as well as cities, create a cumulative effect that would indeed affect the skies of scientific interest.

This regulation, in the words of the ESO representative in Chile, should establish a maximum acceptable level of light pollution for certain areas of astronomical interest, “regardless of how many projects are installed. Thus, when, for example, the accumulated light pollution reaches 1%, the area is considered saturated, and no more bulbs are accepted. That is the new regulation we want to promote.”

“A sky quality standard would allow for the consideration of the cumulative effects of all those who are emitting. Because, eventually, we could find that everyone complies with the regulation, but the sky continues to worsen,” says Unda-Sanzana.

“Here we have the same skies that our ancestors saw, pristine skies. It is very important to continue preserving this place because if it starts to get polluted, we will not be able to continue placing these telescopes here,” concludes De Gregorio-Monsalvo.