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The Atacama Desert in Chile brings together conditions that are almost nonexistent in any other place on Earth: high altitude, extremely dry air, and more than 300 clear nights per year. The region houses some of the most sophisticated telescopes in the world, including the future Extremely Large Telescope. However, light pollution caused by urban expansion, mining, and energy projects is encroaching on the darkest sky on the planet and may compromise decades of astronomical research.
The sky of the Atacama is one of the last places on the planet where it is possible to see the Milky Way with the naked eye, distinguish planets, and perceive details that most humans have lost to the artificial light of cities. The region has become a global hub for astronomy precisely because it offers what telescopes costing billions of dollars need to function: absolute darkness. But light pollution is advancing uncontrollably over northern Chile, and scientists warn that changes may drastically reduce the quality of observations and jeopardize entire scientific projects.
The problem is neither abstract nor distant. A green energy complex was proposed just 10 kilometers from the Paranal Observatory, one of the main astronomical centers in the world. The project was canceled after international pressure from researchers, but the episode revealed that Chilean legislation protecting the night sky is insufficient to block similar initiatives. Every year, new sources of light and human interventions approach the observatories, and what was once described as an ocean of darkness now coexists with the increasing brightness of a desert that has ceased to be isolated.
Why the Atacama sky is considered the most valuable in the world for science
According to information released by the G1, northern Chile combines three conditions that rarely coexist: high altitude that positions the telescopes above much of the atmosphere, extremely dry air that minimizes distortion of the captured signals, and low cloud cover that ensures more than 300 clear nights per year. This combination makes Atacama the most productive place on the planet for astronomical observation, surpassing competitors like Hawaii and the Canary Islands.
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The region concentrates instruments that cost billions of dollars and depend on darkness to operate at maximum capacity. The future Extremely Large Telescope (ELT), under construction by the European Southern Observatory, promises to enhance observation capacity to unprecedented levels, but it will only be able to fulfill this promise if the sky around it remains dark enough to capture signals from billions of light-years away. The quality of the sky depends not only on the absence of clouds: darkness is the central component.
How light pollution destroys the capacity of telescopes
Telescopes capture minimal amounts of light coming from extremely distant objects. When there is artificial lighting in the environment, this pollution mixes with cosmic signals and reduces the contrast of images, compromising resolution and accuracy. An instrument designed to observe distant galaxies may start to operate with performance similar to that of much smaller equipment if it is exposed to excessive brightness.
The impact is not limited to direct light. Projects near the observatories can generate dust, vibrations, and changes in the composition of the local atmosphere, factors that also hinder observations. Even seemingly small sources of light, such as distant urban lighting, are sufficient to interfere with the measurements of instruments calibrated to detect signals from billions of light-years away. In the Atacama, where every photon counts, any increase in light pollution represents a measurable loss of scientific capacity.
The case of the green energy complex 10 km from the Paranal Observatory
The most recent alert about the fragility of the sky of the Atacama arose with the proposal to build a green energy complex about 10 kilometers from the Paranal Observatory. The project would include solar panels and wind turbines that, in addition to operational light, would generate reflections and vibrations incompatible with the astronomical observations conducted at the site.
International pressure from scientists and research institutions led to the cancellation of the project, but the episode exposed serious gaps in Chilean legislation. Researchers assess that current rules are insufficient to prevent new similar initiatives and that the definition of protected astronomical zones needs to be reformulated with stricter criteria. Since then, authorities have been reviewing environmental regulations, but the pace of regulatory changes does not keep up with the speed at which new ventures advance in the region.
The economic expansion that transforms the darkest desert in the world
In recent decades, the Atacama has ceased to be an isolated territory. Mining, energy infrastructure, and urban expansion have transformed the desert into an active economic zone, with lit roads, industrial complexes, and cities growing towards the observatories. Chile is the world’s largest producer of copper, and a large part of the mines is in the same desert that houses the telescopes.
The dilemma is real: the country needs the revenue from mining and the energy transition, but it also depends on the scientific reputation that the Atacama has built over decades. Balancing economic development with the preservation of a resource considered strategic for global science requires regulation that Chile does not yet possess on the necessary scale. For scientists, the equation is clear: if the sky darkens less, the telescopes produce less, and the investment of billions of dollars loses part of its meaning.
The historical precedent that shows loss is real
The risk of losing the sky of the Atacama to pollution is not hypothetical. An international solar observatory operated in Chile in the early 20th century was deactivated after the increase in pollution associated with mining, demonstrating that the degradation of the quality of the sky can render entire scientific projects unfeasible. The precedent serves as a warning for a region that now concentrates incomparably larger astronomical investments.
For researchers monitoring the evolution of the site, the change is visible each year. What was once possible to observe clearly now shows signs of interference, and the trend is worsening as economic activity intensifies. The scientific community argues that the dark sky of the Atacama is a natural resource as valuable as the copper that comes from the mines, with the difference that, once lost, it cannot be recovered.
Did you know that one of the darkest skies in the world is threatened by light pollution, or did you think that only large cities suffer from excess artificial light? Tell us in the comments if you have ever seen the Milky Way with the naked eye and what you think about the dilemma between development and preservation of the night sky.
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