image: The dark skies above ESO’s Paranal Observatory, home to ESO’s Very Large Telescope (VLT), yield breathtaking views so clear and so full of stars that you could almost touch them. Standing atop a platform at VLT, ESO Photo Ambassador Petr Horálek reaches towards a standout object in the sky. You may assume this bright body, like many others in the sky, to be a star, but it is in fact a planet in our Solar System: the gas giant Jupiter. Closer to Earth, the four Unit Telescopes (UTs) that comprise the VLT can be seen in the background. Each UT features an 8.2-metre mirror and they operate synergistically to produce some of the sharpest views of the Universe. Accompanying the four UTs are four smaller, moveable Auxiliary Telescopes (ATs) which have 1.8-metre mirrors. The Chilean Atacama desert once again proves its value as the ideal location for ESO’s VLT. The remoteness of the observatory means that there is very little to no light pollution, which is vital for astronomy and also yields such breathtaking views.
Credit: ESO/P. Horálek
On December 24th, AES Andes, a subsidiary of the US power company AES Corporation, submitted a project for a massive industrial complex for environmental impact assessment. This complex threatens the pristine skies above ESO’s Paranal Observatory in Chile’s Atacama Desert, the darkest and clearest of any astronomical observatory in the world [1]. The industrial megaproject is planned to be located just 5 to 11 kilometres from telescopes at Paranal, which would cause irreparable damage to astronomical observations, in particular due to light pollution emitted throughout the project’s operational life. Relocating the complex would save one of Earth's last truly pristine dark skies.
An irreplaceable heritage for humanity
Since its inauguration in 1999, Paranal Observatory, built and operated by the European Southern Observatory (ESO), has led to significant astronomy breakthroughs, such as the first image of an exoplanet and confirming the accelerated expansion of the Universe. The Nobel Prize in Physics in 2020 was awarded for research on the supermassive black hole at the centre of the Milky Way, in which Paranal telescopes were instrumental. The observatory is a key asset for astronomers worldwide, including those in Chile, which has seen its astronomical community grow substantially in the last decades. Additionally, the nearby Cerro Armazones hosts the construction of ESO’s Extremely Large Telescope (ELT), the world’s biggest telescope of its kind — a revolutionary facility that will dramatically change what we know about our Universe.
“The proximity of the AES Andes industrial megaproject to Paranal poses a critical risk to the most pristine night skies on the planet,” highlighted ESO Director General, Xavier Barcons. “Dust emissions during construction, increased atmospheric turbulence, and especially light pollution will irreparably impact the capabilities for astronomical observation, which have thus far attracted multi-billion-Euro investments by the governments of the ESO Member States.”
The unprecedented impact of a megaproject
The project encompasses an industrial complex of more than 3000 hectares, which is close to the size of a city, or district, such as Valparaiso, Chile or Garching near Munich, Germany. It includes constructing a port, ammonia and hydrogen production plants and thousands of electricity generation units near Paranal.
Thanks to its atmospheric stability and lack of light pollution, the Atacama Desert is a unique natural laboratory for astronomical research. These attributes are essential for scientific projects that aim to address fundamental questions, such as the origin and evolution of the Universe or the quest for life and the habitability of other planets.
A call to protect the Chilean skies
“Chile, and in particular Paranal, is a truly special place for astronomy — its dark skies are a natural heritage that transcends its borders and benefits all humanity,” said Itziar de Gregorio, ESO’s Representative in Chile. “It is crucial to consider alternative locations for this megaproject that do not endanger one of the world's most important astronomical treasures.”
The relocation of this project remains the only effective way to prevent irreversible damage to Paranal's unique skies. This measure will not only safeguard the future of astronomy but also preserve one of the last truly pristine dark skies on Earth.
Notes
[1] A study by Falchi and collaborators, published in 2023 in Monthly Notices of the Royal Astronomical Society, compared light pollution at all 28 major astronomical observatories, finding Paranal to be the darkest site among them.
Contacts
Francisco Rodríguez
ESO Media Relations Officer
Santiago, Chile
Tel: +56 2 2463 3151
Email: francisco.rodriguez@eso.org
Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Tel: +49 89 3200 6670
Email: press@eso.org