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 Ohio State University. The signal bore expected hallmarks of potential non-terrestrial and non-solar system origin. It lasted for 72 seconds, the full duration Big Ear observed it, but has not been detected again. It has been the focus of attention in the mainstream media when talking about SETI results.
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 comment became the name of the signal.
In a 2016 paper, Astronomers Antonio Paris and Evan Davies proposed that the signal could have been caused by a comet orbiting in the inner solar system. The 2016 paper identifies two comets, 266P/Christensen and P/2008 Y2 (Gibbs), as candidates for the wow signal, as they both were suspected to be in the area in August 1977. Both of these comets have large hydrogen clouds surrounding them that could produce the kind of signal detected in 1977. Paris spent about four months in late 2016 and early 2017 with a telescope pointed at comet 266P. He claims that he found strong signals of the same type as the Wow! signal.
A spokesperson from the OSU Radio Observatory, where the Wow! signal was detected, has reached out to express skepticism of this discovery. Specifically, the spokesperson notes that both comet 266P and P/2008 were too far away to have caused the signal, and that there's no prior evidence suggesting that comets can create the type of signal spotted in 1977. In particular, the Wow! signal only lasted for a little over a minute, which would be unusual for a comet.