The Wow! signal remains the strongest candidate for a detected extraterrestrial radio transmission, though it has never been explained or reproduced.
Key Facts
- Detection date
- August 15, 1977
- Telescope
- Big Ear, Ohio State University
- Signal duration
- 72 seconds (full observation window)
- Signal intensity code
- 6EQUJ5
- Apparent source direction
- Constellation Sagittarius
- Subsequent detections
- None confirmed
By the Numbers
Location
Cause → Event → Consequence
Ohio State University's Big Ear radio telescope was operating as part of the Search for Extraterrestrial Intelligence (SETI) program, systematically scanning the sky for narrowband radio signals that might indicate non-natural, non-terrestrial origin. On August 15, 1977, the telescope recorded an unusually strong signal appearing to originate from the direction of Sagittarius.
Astronomer Jerry R. Ehman, reviewing the recorded telescope data days after the observation, noticed a signal of exceptional intensity encoded as '6EQUJ5' on the computer printout. He circled it and wrote 'Wow!' beside it. The signal lasted the full 72-second window Big Ear could observe any given point in the sky, matching predicted characteristics of an extraterrestrial narrowband transmission.
Despite repeated follow-up searches, the signal was never detected again, and no confirmed terrestrial or astrophysical explanation has been established. Hypotheses including space debris reflections, interstellar scintillation, and comet hydrogen clouds were considered but not confirmed. The event has driven ongoing scientific debate about rare astrophysical phenomena and inspired continued SETI research efforts and popular culture references.