Astronomers warn proposed space mirrors would create severe light pollution, outshining the full moon
A study finds that each sun-reflecting mirror planned by startup Reflect Orbital would appear 40 times brighter than the full moon to observers in its beam, erasing all stars from view. The company has received FCC approval for a demonstration satellite with a 60-foot mirror, and plans to launch thousands more. Princeton astrophysicist Gaspar Bakos says the effect would be worse than city lights like London's.
The study's calculations rely on decades-old atmospheric light-scattering data, which Bakos says have been validated in real-world conditions. Reflect Orbital's operational mirrors would measure 174 by 174 feet, far larger than the 60-foot demonstration satellite EARENDIL-1, which received FCC approval for a 373-mile-high orbit. The company's stated goals include extending solar power plant operations into nighttime and illuminating disaster zones, but its broader plan involves deploying tens of thousands of mirrors.
Bakos and other astronomers filed formal objections with the FCC, arguing that previous estimates were dismissed by the company. The new modeling shows each mirror's 3.4-mile-wide beam would create twilight-level sky brightness at its center, stripping away all visible stars for observers beneath it. The research provides concrete figures where only rough projections existed before, strengthening the case against the proposal.
This dispute could reshape how orbital commercial ventures are regulated, as the FCC's approval of EARENDIL-1 sets a precedent for future space-based illumination projects. Astronomers, environmental groups, and pilot associations may face a permanently altered night sky if thousands of mirrors launch, affecting scientific research, navigation, and cultural heritage. The tension between commercial innovation and shared environmental resources may force regulators to weigh private interests against public access to dark skies, potentially influencing international space policy for years to come.