To protect night-sky observations, astronomers propose a 100,000-satellite limit

A new study from the European Southern Observatory (ESO) warns that ground-based astronomy could become effectively impossible if the number of satellites in low Earth orbit exceeds 100,000. The research, which is the first to quantify how satellite brightness and density affect telescope observations, recommends capping the number of faint satellites, those below naked-eye visibility, at that threshold to preserve humanity’s ability to study the universe from the planet’s surface.

"devastating consequences for astronomy"

The study, as reported by Hacker News, examined proposals that would place over 1.7 million satellites into orbit, including extremely bright ones, and found that such a buildup would have "devastating consequences for astronomy." The analysis calculates how satellite constellations would make the night sky brighter, overwhelming modern telescopes with streaks of reflected light.

"the public has not consented to a fundamentally transformed night sky"

Space noted that the tension between commercial space ambitions and the preservation of ground-based observatories is at the heart of the conflict. The study highlights that orbiting data centers, sun-reflecting mirrors, and other unregulated projects are driving the threat, all without public agreement on a dramatically altered sky.

Both ispreview.co.uk and Space reported that if the satellite count passes 100,000, including objects invisible to the naked eye, the world’s most advanced telescopes would be rendered obsolete. ispreview.co.uk described how satellite streaks are increasingly ruining telescope images, a problem the study warns will only worsen as mega-constellation plans accelerate.

ispreview.co.ukESO Study Warns Satellite Megaconstellations Could Cripple Ground-Based Astronomy

The ESO research also raises concerns about broader impacts on health and the environment from these megaconstellations, according to Hacker News. As commercial space ventures push forward, astronomers are calling for regulatory limits to ensure that ground-based astronomy is not sacrificed in the process.