Planned 1.7 Million Satellites Pose 'Existential Threat' to Astronomy, Study Warns

A new study has issued a stark warning: the planned launch of 1.7 million satellites into Earth's orbit by various companies in the coming years poses an "existential threat" to humanity's ability to observe the universe. Researchers from the European Southern Observatory (ESO), who conducted the study published in Astronomy & Astrophysics, argue that these vast constellations of extremely bright satellites will have "devastating consequences for astronomy," calling for a strict limit of 100,000 orbiting satellites to preserve our view of the night sky. The current number of satellites orbiting Earth stands at approximately 14,000, a figure that has surged recently, largely due to projects like Elon Musk's Starlink. However, this is merely the beginning. SpaceX plans to launch over one million satellites by 2028 to power the artificial intelligence boom. Other ambitious projects, such as E-Space's "Cinnamon" plans and Chinese constellations CTC-1 and CTC-2, aim to add hundreds of thousands more. Most alarmingly, U.S. startup Reflect Orbital intends to deploy 50,000 massive satellites equipped with giant mirrors designed to reflect sunlight back to Earth, ostensibly to provide night-time illumination. These planned mega-constellations threaten to transform the night sky dramatically. Olivier Hainaut, an ESO astronomer and lead author of the study, explained that when a satellite crosses the field of view, it creates a bright streak, obscuring whatever lies behind it. While currently manageable, the leap from 14,000 to 1.7 million satellites would create insurmountable problems. The Reflect Orbital satellites, even when not directly aimed at observers, are projected to be as bright as Venus, potentially making the entire night sky up to four times brighter and rendering almost all images from advanced observatories like the Vera C. Rubin Observatory in Chile unusable. Beyond the direct impact on astronomical research, the proliferation of bright satellites introduces broader environmental and biological concerns. Light pollution from these constellations can disrupt the biological clocks of humans and animals, interfering with delicate ecosystems. Furthermore, the sheer scale of launches raises questions about energy consumption, environmental footprint, and the escalating risk of space debris. The "Kessler syndrome," a dangerous chain reaction of collisions, becomes an increasingly plausible threat as orbital traffic intensifies. The scientific community is urging regulators to take decisive action. The new study served as a crucial basis for ESO's response to the applications from Reflect Orbital and SpaceX before the U.S. Federal Communications Commission (FCC), in collaboration with the U.K.'s Royal Astronomical Society and the International Astronomical Union. Betty Kioko, ESO's institutional affairs officer, emphasized that for optical astronomy, this represents an "existential threat," urging regulators to share this critical view. Reflect Orbital has stated it is commissioning independent research and is committed to dialogue, promising to keep satellites "off" by default and avoid redirecting light near observatories. The ball, however, remains firmly in the FCC's court.