WOW! Signal

The Wow! signal was a strong narrowband radio signal detected by Dr. Jerry R. Ehman on August 15, 1977, while working on a SETI project at the Big Ear radio telescope of The Ohio State University. Amazed at how closely the signal matched the expected signature of an interstellar signal in the antenna used, Ehman circled the signal on the computer printout and wrote the comment "Wow!" on its side, this how the signal became to be known as the Wow signal.

The signal bore expected hallmarks of potential non-terrestrial and non-solar system origin. It lasted for the full 72-second duration that Big Ear observed it, but has not been detected again.

There are numerous theories casting speculation on the signal's true origin, mainly that if it was artificially created, it then would have been found the next 50 times they searched for the signal, but it was not.

Source: en.wikipedia.org/wiki/Wow!_signal