Wow! signal
On August 15, 1977, a strong narrowband radio signal was received by The Ohio State University's Big Ear radio telescope, in the United States, then assigned to a SETI project. The signal appeared to come from the constellation Sagittarius and bore the expected hallmarks of extraterrestrial origin.
Astronomer Jerry R. Ehman discovered the anomaly a few days later, while reviewing the recorded data. He was so impressed by the result that he circled the reading on the computer printout and wrote the comment Wow! on its side, which is how the event has since been referred.
The entire signal sequence lasted for the full 72-second window that Big Ear was able to observe it, but has not been detected since, despite several subsequent attempts by Ehman and others. Though none of the many hypotheses advanced to date adequately explains the source of the emission, and a natural origin has not been ruled out, the Wow! signal remains the strongest candidate ever detected for an alien radio transmission.
In 1973, after completing an extensive survey of extragalactic radio sources, The Ohio State University assigned the now-defunct Big Ear telescope, then located near the Perkins Observatory in Delaware, Ohio, to the scientific search for extraterrestrial intelligence (SETI), in what would have become the longest-running program of this kind in history.
Over a decade earlier, in a 1959 paper, Cornell physicists Philip Morrison and Giuseppe Cocconi had also speculated that any extraterrestrial civilization attempting to communicate via radio signals might choose to do so using a frequency of 1420 megahertz, which is naturally emitted by hydrogen, the most common element in the universe and therefore likely familiar to all technologically advanced civilizations.
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