ESO study urges cap of 100,000 satellites for astronomy

Astronomers are urging regulators to impose strict limits on the number of satellites in Earth's orbit, warning that proposed mega-constellations totaling 1.7 million spacecraft pose an existential threat to ground-based astronomy. A new study from the European Southern Observatory (ESO) concludes that to protect the night sky, the total number of satellites must be capped at around 100,000, and they must be dim enough to remain invisible to the naked eye.

The peer-reviewed research, led by ESO astronomer Olivier Hainaut and accepted for publication in the journal Astronomy & Astrophysics, is the first to comprehensively calculate how large, bright satellite constellations increase background sky brightness and degrade astronomical observations. The number of active satellites has surged from a few thousand to over 14,000 since 2019, largely due to the rapid expansion of SpaceX's Starlink telecommunications network. Current proposals, however, would multiply that number by more than a hundred.

SpaceX has announced plans to launch up to one million additional satellites to serve as orbital data centers for artificial intelligence applications. Another U.S. startup, Reflect...