In 1977, astronomer Jerry R. Ehman observed a data signal so unique he drew a red circle around it and wrote “Wow!” to emphasize the discovery. The source of the signal was never identified, leading some to say it was aliens. But a new study suggests it wasn’t aliens at all—but rather a hydrogen cloud caused by comets.
The Wow! signal, as it’s known, was detected by Ehman while he was working on a SETI project at Ohio State University’s now defunct Big Ear radio telescope. While scanning the skies for evidence of extraterrestrial radio messages, he focused on a portion of the radio spectrum that resembles hydrogen. On August 15, 1977, he documented an extraordinary 72-second sequence of unusual intensity. Intriguingly, the signal appeared to have emanated from a M55, a globular cluster located in the constellation Sagittarius.
Follow-up analyses ruled out satellite interference, or that the signal was reflected from the Earth’s surface. Naturally, some people insisted it was an extraterrestrial message, a claim that’s never been proven. (For what it’s worth, Ehman never believed it was caused by aliens.)