The RATAN-600 radio telescope is a ring of hundreds of aluminum panels on a mountainside in Karachay-Cherkessia. In the spring of 2018, its mirror caught radio waves from sixteen red dwarfs — small, dim, but very long-lived stars. Each of them has planets similar to Earth in size and located in the "habitable zone": not too hot, not too cold, where water can remain liquid.

Scientists turned on receivers at four frequencies, like tuning a radio to different stations. The range from 2.3 to 22 gigahertz covers both natural cosmic noise and possible artificial signals. Each star was listened to from three to twenty-seven times, a few seconds per pass. The result: silence. Not a single flare, not a single steady signal.

Silence does not mean emptiness. It means a limit: if these stars do harbor civilizations, their radio transmitters are either weaker than our radars or silent. The observations also showed that the red dwarfs were calm that month — no powerful flares that could disrupt life on nearby planets.

The radio telescope has gone quiet, but its dish is already turning toward other stars. Every hour of silence is not a waste of time but a new boundary on the map of the search.