Satellites are becoming a growing concern for astronomers as they outshine nearly all but the brightest stars in the sky, according to a study conducted by Imperial College. The study focused on the BlueWalker 3 communications satellite, which was launched last year and has the largest antenna array of any commercial satellite.
Researchers discovered that sunlight reflecting off the array makes the satellite shine as brightly as the brightest stars in certain constellations. Ground observations also revealed that the satellite occasionally becomes hundreds of times brighter than the recommended dark sky guidelines set by the International Astronomical Union (IAU). Additionally, the transmitted frequencies could interfere with radio astronomy.
AST SpaceMobile, the company that launched the satellite, plans to deploy a hundred more to create a space-based cellular broadband network. However, astronomers are expressing increasing concerns about the growing congestion of objects in space. Dr. Mike Peel from Imperial College’s Physics Department and a member of the IAU’s dark skies team stated that the brightness of satellites like BlueWalker 3 doesn’t just affect astronomical images but can also force telescopes to shut down temporarily, potentially causing the loss of important transient events.
The number of satellites orbiting Earth has increased four-fold since 2019, with more than 8,000 currently in orbit. The IAU’s recommendation is that satellites should not exceed a certain level of brightness, known as the 7th magnitude. However, BlueWalker 3 was found to be over 400 times brighter than this limit.
Imperial College researchers hope that by highlighting these issues, AST SpaceMobile will address the concerns and invest in mitigation strategies before future launches. The company has expressed intentions to avoid frequencies used by radio astronomers and is exploring options such as “roll-tilting maneuvers” to reduce sunlight reflection and anti-reflective materials for next-generation satellites.
With the exponential growth of satellite deployments expected in the coming decades, astronomers stress the potential impact on the night sky and call for measures to preserve the integrity of astronomical observations for everyone.