The Wow! Signal

The sole known proof of the presence of extraterrestrial life was discovered by astronomers working at Ohio State University's Big Ear telescope in August 1977. The signal, which lasted exactly 72 seconds, was so strong that one of the observers, Jerry Ehman, scrawled "Wow!" next to the data. They didn't know where it originated from, but it had the same frequency as hydrogen.

The puzzle wasn't answered until the end of 2016, when a group of astronomers considered comets as a potential explanation because comets typically have hydrogen clouds surrounding them. Indeed, they located two of them, P/2008 Y2(Gibbs) and 266/P Christensen, both of which had not yet been detected but had been in the area when the signal was captured. As scientists observed one of them from the end of 2016 to the beginning of 2017, 266/P, it even produced signals that were similar to those of the Wow! signal.