[syhprum (OP)]

The WOW event was the reception of a short lived very strong and monochromatic radio frequency burst detected in 1977 by  a radio telescope .
This led to speculation that is was made by "aliens" as no natural source could be identified.

[Kryptid]

Last I heard there was a hypothesis that the signal was caused by a comet. I forget the exact mechanism involved, but there was a GoFundMe project set up specifically to finance a test to see if a signal similar to the WOW signal could be reproduced from comet observations.