Why the Interstellar Visitor 3I/ATLAS Remains Silent on the Radio ✛ ✎

Imagine you're trying to hear a faint alarm clock from one room when an orchestra is playing loudly. If you set up several microphones, you can catch the difference: the alarm clock's sound will be louder in the nearest microphone. That's roughly how the method used to observe the interstellar object 3I/ATLAS worked — an unusual comet that flew in from another star system. The giant FAST radio telescope, with its multiple beams as 'ears', listened to the ether for a long time, and mathematical processing, akin to separating mixed voices in a recording, searched for rhythmic notes.

Alas, no artificial signals were found. Analysis based on entropy — a measure of how much energy is concentrated in the desired beam rather than smeared everywhere — showed that all suspicious bursts turned out to be either terrestrial interference or random noise. If there is a radio beacon operating on 3I/ATLAS, its power is no more than 0.146 watts — weaker than a flashlight bulb. The search was conducted at frequencies where hydrogen emits (21 centimeters) — this spectral fingerprint is considered a common language for interstellar communication.