Case · sin_explicacion
The Wow! signal (1977)
On August 15, 1977, Ohio State's Big Ear radio telescope picked up a strong narrowband radio signal; astronomer Jerry Ehman circled it on the printout ('6EQUJ5') and wrote 'Wow!'.
What is claimedBecause of its frequency (~1420 MHz, the hydrogen line) and strength, it was considered a candidate extraterrestrial signal. It never repeated.
Skeptical viewIn 2017 a comet hydrogen cloud was proposed as the source, but Ehman and others reject it; it remains without a confirmed explanation, terrestrial or otherwise.
Related: 'Oumuamua (2017)
Sources — here nothing is invented: Jerry Ehman / Big Ear (Ohio State) · Wikipedia