The study explored how hidden electromagnetic leakage might look to extraterrestrials up to 200 light-years from Earth, if they had state-of-the-art radio telescopes like our own. Theoretically, it also suggests this is how far we would be able to look to spot aliens who have evolved to use a similar level of technology.
Preliminary results revealed at the Royal Astronomical Society's National Astronomy Meeting 2025 in Durham show how worldwide aviation hubs such as Heathrow, Gatwick and New York's JFK International Airport give off clues to our existence.
By carefully simulating how these radar signals spread out from Earth over time and space, the researchers looked at how visible they would be from nearby stars such as Barnard's Star and AU Microscopii.
They found that airport radar systems, which sweep the skies for airplanes, send out a combined radio signal of 2x1015 watts, enough to be picked up as far as 200 light-years away by telescopes comparable to the Green Bank Telescope in West Virginia.
To put that distance into context, the nearest potentially habitable world beyond our solar system is Proxima Centauri b, which is 4 light-years away. That would still take a spacecraft using current technology thousands of years to get there.
Military radar systems, which are more focused and directional, create a unique pattern - like a lighthouse beam sweeping the sky - have an accumulated peak emission reaching about 1x1014 watts in a given field-of-view of the observer.
This, lead researcher Ramiro Caisse Saide at the University of Manchester said, would look "clearly artificial to anyone watching from interstellar distances with powerful radio telescopes".
"In fact, these military signals can appear up to a hundred times stronger from certain points in space, depending on where an observer is located," the PhD student added.
"Our findings suggest that radar signals - produced unintentionally by any planet with advanced technology and complex aviation system - could act as a universal sign of intelligent life."
He said the research not only helps guide the search for extraterrestrial civilisations by identifying promising technosignatures, but also deepens our understanding of how human technology may be seen from space.
"By learning how our signals travel through space, we gain valuable insights into how to protect the radio spectrum for communications and design future radar systems," said co-researcher Professor Michael Garrett, of the University of Manchester.
"The methods developed for modelling and detecting these weak signals can also be used in astronomy, planetary defence, and even in monitoring the impact of human technology on our space environment."
Caisse Saide, a PhD student, added: "In this way, our work supports both the scientific quest to answer the question 'Are we alone?' and practical efforts to manage the influence of technology on our world and beyond."
Research Report:Examining Airport Civilian and Military Radar Leakage as a Detectable Marker for Extraterrestrial Civilizations
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