Astronomers are shifting their approach in the quest for signs of extraterrestrial intelligence by examining potential alien artefacts within our Solar System. A new study published in the Monthly Notices of the Royal Astronomical Society outlines an innovative technique that employs Earth’s shadow to filter out interference from human-made satellites and space debris.
For decades, researchers have relied on radio telescopes and optical instruments to scan the skies for artificial signals. The increasing clutter of thousands of satellites and millions of pieces of space debris has complicated these efforts, making it challenging to identify objects of interest. Lead researcher Beatriz Villarroel from Stockholm University and her international team sought a solution by utilizing Earth’s shadow, a natural barrier that blocks sunlight from reflecting off these artificial objects.
Every night, Earth casts a cone-shaped shadow into space, creating a zone free from direct sunlight. This shadow spans roughly 8-9 degrees at geosynchronous orbit, approximately 35,700 kilometers (22,200 miles) above the Earth. Since most human satellites do not emit optical light—except for rare cases like communication lasers or spacecraft thrusters—any bright flashes or streaks detected within this shadow could indicate something more extraordinary.
The researchers conducted their analysis using images from the Zwicky Transient Facility (ZTF), a telescope located in California that systematically surveys the sky for changing objects. They scrutinized over 200,000 images, focusing specifically on those taken within Earth’s shadow. Their automated search system, named NEOrion, identified thousands of candidates, including mysterious streaking objects and point source flashes.
While most of these candidates were confirmed as meteors, aircraft, or known asteroids, one intriguing case stood out. The team discovered an uncatalogued object moving significantly faster than typical asteroids, which was not listed in any existing space object databases. Unfortunately, the researchers were unable to confirm its identity, leaving it a mystery that still requires further investigation.
In addition to their primary method, the study explored other innovative approaches. The team examined pre-1957 astronomical photographs and analyzed the color spectra of suspicious objects to determine materials that may have been weathered by prolonged exposure to space. Although this proof of concept study did not definitively identify any alien technology, it demonstrates the feasibility of systematic searches for extraterrestrial artefacts using current telescopes and new analytical techniques.
Looking ahead, the researchers are developing the ExoProbe project, a network of telescopes specifically designed for this type of search. This ambitious initiative aims to conduct multiple simultaneous observations to accurately measure distances to mysterious objects, enhancing the search for extraterrestrial probes.
The findings from this study not only represent a significant advancement in the search for extraterrestrial intelligence but also highlight the potential for innovative methods in astrobiology. As researchers continue to explore the cosmos, this unique approach may lead to new discoveries that could reshape our understanding of life beyond Earth.
