The Wow! Signal
For 72 seconds, a radio telescope in Ohio picked up a signal so strong that the astronomer reading the printout wrote 'Wow!' next to it.
What was reported
On 15 August 1977, Ohio State University's Big Ear radio telescope, which was scanning the sky for signals from other civilisations, recorded a strong, narrow burst of radio waves from the direction of the constellation Sagittarius. It lasted about 72 seconds, roughly as long as it took the sky to drift past the telescope.
Days later, the volunteer astronomer Jerry Ehman circled the code '6EQUJ5' on the printout and wrote 'Wow!' beside it. The signal was close to the frequency of hydrogen, which scientists had suggested others might use to signal. Searches of the same patch of sky since then have never found it again.
Explanations offered
No explanation has been confirmed. A 2017 suggestion that it came from passing comets was widely rejected. In 2024, researchers proposed that a cold hydrogen cloud was briefly brightened by a burst from a distant star, which would make it a rare natural event. Others still consider it the best candidate signal ever recorded.
- When
- 15 August 1977
- Where
- Big Ear radio telescope, Delaware, Ohio, USA
- Witnesses
- Recorded by a radio telescope; spotted by astronomer Jerry Ehman
- Status
- Unexplained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.