‘Cosmic Static or Something More? The Full List of Comets Humanity Has Ever Detected Sending a Radio Signal of Any Kind.’
The question sounds simple—almost too simple—until you realize how few people on Earth can actually answer it without guessing: How many comets have ever been recorded transmitting a radio signal of any kind? I asked this question out loud after MeerKAT’s discovery of the narrow-band 1665 and 1667 MHz absorption signature from 3I/ATLAS, and the deeper I went, the more obvious it became that only a tiny catalog of comets has ever produced anything detectable in the radio spectrum. And none—absolutely none—have behaved like 3I/ATLAS.
In the history of planetary science, radio detection of comets has been rare, difficult, and scientifically valuable. Traditional comets sometimes emit microwave signatures from hydroxyl radicals, sometimes show thermal radio emissions from their comae, and sometimes reflect radar waves that reveal the size and rotation of their nuclei. All of these are natural processes. All of them are expected. And yet the list of comets that have ever been confirmed through radio observation is shockingly short.
