The Wow! signal was a strong narrowband radio signal detected on August 15, 1977, by Ohio State University's Big Ear radio telescope in the United States, then used to support the search for extraterrestrial intelligence. The signal appeared to come from the direction of the constellation Sagittarius and bore the expected hallmarks of extraterrestrial origin.
The entire signal sequence lasted for the full 72-second window during which Big Ear was able to observe it, but has not been detected since, despite several subsequent attempts by Ehman and others. Many hypotheses have been advanced on the origin of the emission, including natural and human-made sources, but none of them adequately explain the signal.
Although the Wow! signal had no detectable modulation—a technique used to transmit information over radio waves—it remains the strongest candidate for an extraterrestrial radio transmission ever detected.
When astronomers tried to follow up, the signal was gone. It happened just this one time, and then not anything else like it, not from this region, or any other region in the the sky.
https://en.m.wikipedia.org/wiki/Wow!_signal
https://www.universetoday.com/122409/what-was-the-wow-signal/
The entire signal sequence lasted for the full 72-second window during which Big Ear was able to observe it, but has not been detected since, despite several subsequent attempts by Ehman and others. Many hypotheses have been advanced on the origin of the emission, including natural and human-made sources, but none of them adequately explain the signal.
Although the Wow! signal had no detectable modulation—a technique used to transmit information over radio waves—it remains the strongest candidate for an extraterrestrial radio transmission ever detected.
When astronomers tried to follow up, the signal was gone. It happened just this one time, and then not anything else like it, not from this region, or any other region in the the sky.
https://en.m.wikipedia.org/wiki/Wow!_signal
https://www.universetoday.com/122409/what-was-the-wow-signal/