Astronomers Warn 100,000 Satellites Could End Ground-Based Sky Observation

The proliferation of satellites in Earth's orbit is posing a critical threat to ground-based astronomy, with scientists warning that exceeding 100,000 operational satellites could effectively end astronomical research as we know it. The surge in launches, largely driven by private companies like SpaceX aiming to establish vast satellite constellations, is creating unprecedented light pollution.

A study published in 'Astronomy & Astrophysics' by the European Southern Observatory (ESO) simulated the impact of proposed satellite constellations. Researchers found that if the currently planned 1.76 million satellites are deployed, ground-based astronomical observations would suffer "fatal damage." The number of satellites already in orbit has reached 16,100, a sharp increase since 2019, but the current plans far exceed this growth rate.

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If more than 100,000 satellites are in orbit, ground-based astronomy will effectively become impossible.

Specific concerns are raised about SpaceX's proposed 1 million "space data center" satellites and Reflect Orbital's 50,000 "space mirror" satellites. The sheer number of SpaceX satellites could mean hundreds, or even thousands, appearing in telescope views simultaneously each night, comparable to the number of stars visible to the naked eye. Reflect Orbital's satellites, designed to be exceptionally bright, could appear four times brighter than a full moon, significantly increasing skyglow.

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If the more than 1.7 million satellites currently planned are launched, ground-based astronomical observations will be fatally damaged.

This light pollution, encompassing both diffuse and scattered light, threatens to obscure faint celestial objects and fundamentally alter the night sky. Researchers estimate that the deployment of 50,000 "space mirror" satellites could make the night sky up to three to four times brighter. The study emphasizes that this light pollution not only hinders astronomical observation but could also impact the detection of potentially hazardous asteroids and disrupt Earth's ecosystems.

To mitigate these effects, the researchers advocate for strict regulations, including limiting the apparent magnitude of satellites to below 7th magnitude (significantly dimmer than what is visible to the naked eye) and capping the total number of satellites at 100,000. They stress that 100,000 is the "red line" for maintaining data loss within acceptable technical limits, beyond which astronomical research becomes untenable. The researchers also warn that the low Earth orbit, often described as a "celestial beach," must be preserved for future generations.

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100,000 is the red line for maintaining data loss within acceptable technical limits.