Since the first modern SETI (Search for ExtraTerrestrial Intelligence) studies tried to detect alien transmissions in the early 1960s, scientists on Earth have been on the alert for strange cosmic signals with no reasonable explanation. So far, they haven’t positively identified any signals as evidence of intelligent alien life among the stars, but the search continues.

Most SETI telescope searches aim to observe a vast expanse of sky or zero in on a specific star system or group of stars. They usually try to intercept signals that potential aliens could have aimed at Earth or those that pass close by. But what if aliens are transmitting messages from one exoplanet to another instead? If they exist, we may now have a way to eavesdrop on alien conversations, leveling up humanity’s search for intelligent life far from Earth.

Working with his team at Penn State University, astronomer Nick Tusay, a graduate student working on his Ph.D., came up with a new technique that tests indicate would detect alien radio chatter. From our Earthly point of view, we can observe when one exoplanet—a planet that is not part of our solar system—passes in front of and blocks another. This is called occultation. However, the occulting planet does not always completely cover the planet behind it. So, any message a hypothetical alien transmits from the occulted planet can spill over into space, and our radio telescopes could detect it.

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