For decades, astronomers have searched for signs of extraterrestrial intelligence using radio telescopes and optical instruments, scanning the skies for artificial signals. Now, researchers are taking a different approach, this time looking much closer to home for alien artifacts that might already be in our solar system.
A new study published in the Monthly Notices of the Royal Astronomical Society describes an innovative method for detecting potential extraterrestrial probes near Earth. Their innovative approach: to use Earth's shadow as a natural filter to eliminate interference from human-made satellites and space debris.
Modern skies are cluttered with thousands of satellites and millions of pieces of reflective debris, making it extremely difficult to spot anything unusual. This "contamination" poses a major challenge for anyone trying to identify non-human objects in space. Lead researcher Beatriz Villarroel from Stockholm University and her international team needed a way to filter out this noise.
This is why they turned to Earth's shadow. Every night, Earth casts a cone-shaped shadow into space where direct sunlight cannot reflect off satellites or debris. This creates an ideal "clean" search zone. The shadow's base spans roughly 8–9 degrees for objects at geosynchronous orbit, about 35,700 kilometers above Earth.
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