What happened
On the evening of August 15, 1977, Ohio State University’s Big Ear radio telescope, which was running a SETI program, recorded a signal near 1420 MHz – the hydrogen line, which theorists considered a natural choice for civilizations trying to make contact. A few days later, astronomer Jerry Ehman, reviewing the printouts, circled the character string “6EQUJ5,” which indicated a sharp rise in intensity, and wrote “Wow!” in the margin. The signal rose and faded over 72 seconds, exactly as a source in the sky should appear when swept by the beam of a fixed telescope rotating with the Earth. It came from the direction of the constellation Sagittarius. Ehman and others repeatedly pointed telescopes at the same spot afterward, but the signal was never received again.
Witnesses
It was recorded automatically by the instruments of the Big Ear radio telescope; the anomaly was noticed in the data by astronomer Jerry Ehman, who was working as a volunteer.
Explanations and hypotheses
The signal does not resemble typical terrestrial interference, and the 1420 MHz band is protected for radio astronomy. A 2017 hypothesis involving hydrogen clouds around two comets was rejected by astronomers. In 2024, researchers from the Planetary Habitability Laboratory at the University of Puerto Rico proposed that the source may have been a sudden brightening of a cold hydrogen cloud excited by radiation from a star. The hypothesis of an extraterrestrial civilization remains unconfirmed.
Unexplained There is no convincing explanation.
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