Scientists at the European Southern Observatory (ESO) have, for the first time, comprehensively assessed the impact of satellites on observations of the night sky. The results are alarming: if the ambitious plans of private companies are realized, ground-based astronomy could suffer devastating consequences. To save science, researchers propose setting a strict limit of no more than 100,000 spacecraft in near-Earth orbit. Details of this study will soon be published in Astronomy & Astrophysics.
Today, more than 14,000 satellites orbit our planet, and in less than three years this number has almost doubled. Yet this is only the beginning. Corporations such as SpaceX and startups such as Reflect Orbital propose launching a total of about 1.7 million new spacecraft into space.
For astronomers, this is a true catastrophe. By reflecting sunlight, satellites appear much brighter than distant cosmic objects. As they pass above telescopes, they leave dazzling streaks in images, completely obscuring everything behind them. According to ESO astronomer Olivier Hainaut, the situation is rapidly worsening, and the current plans of companies are already exceeding what science can withstand.
Elon Musk, whose company plans to launch up to one million spacecraft, recently stated that space is “huge” and that there is enough room for everyone. Another company, California-based Reflect Orbital, intends to deploy 50,000 satellites with space mirrors to illuminate Earth even at night. For astronomers, however, such initiatives mean the inability to study exoplanets, distant galaxies, and even to track potentially dangerous asteroids near Earth.
Simulation of a Space Catastrophe
To understand the real scale of the threat, scientists modeled the motion, orbits, and brightness of all existing and planned satellite constellations. The results are striking. SpaceX’s megaconstellation would leave dozens of bright trails in every VLT telescope image just two hours after nightfall. This would lead to the loss of nearly 28% of the field of view. And this assumes that the satellites are sufficiently dim. If their brightness exceeds the norm, most images from the highly sensitive Vera C. Rubin Observatory would become completely unusable.
The situation is even worse with Reflect Orbital’s space mirrors. The study shows that the trail from a single such spacecraft could ruin an observation, while the deployment of the entire planned fleet would result in the complete loss of all night-sky images taken by cameras of the type installed at the Rubin Observatory.
Where Is the Line of Compromise?
Based on the simulations, ESO researchers proposed a compromise threshold: 100,000 satellites with brightness below 7th magnitude, meaning they would be invisible to the naked eye.
“This is not a hard number,” Olivier Hainaut noted. “Of course, I would prefer to see 50,000. But 100,000 causes data losses at roughly the same level as ordinary technical equipment failures.” If the spacecraft are brighter, this limit would have to be significantly reduced.
The future of the night sky now lies in the offices of the U.S. Federal Communications Commission (FCC), which is reviewing applications from SpaceX and Reflect Orbital to deploy their networks. The scientific community hopes that regulators will recognize the threat to optical astronomy and make a decision in favor of preserving our access to the mysteries of the Universe.
Earlier, we reported on how SpaceX agreed to make Starlink satellites harmless to astronomy.
According to ESO
