The Wow! signal
Ohio State University's Big Ear telescope recorded a strong narrowband radio signal on 15 August 1977. Astronomer Jerry Ehman spotted it on a printout days later and wrote "Wow!" beside it.
On 15 August 1977 Ohio State University's Big Ear telescope recorded a strong narrowband signal. The telescope was then in use for the search for extraterrestrial intelligence. A few days later Dr. Jerry Ehman was reading the computer printout and noticed it. According to the Big Ear observatory's own account, he saw it as the most intense narrowband signal the telescope had received, and wrote "Wow!" in the margin.
National Geographic reports that the signal came from the area of Sagittarius and ran for 72 seconds. Its strength was 30 times that of the surrounding background noise, at 1,420 megahertz, a frequency very close to the hydrogen line of neutral hydrogen atoms. Wikipedia says it appeared to come from the direction of Sagittarius and showed expected hallmarks of extraterrestrial origin.
The observatory's account lists several people who analysed the signal afterwards, including Dr. John D. Kraus, director of the Ohio State radio observatory.
"The Wow! signal was a strong narrowband radio signal detected on August 15, 1977, by Ohio State University's Big Ear radio telescope in the United States, then used to support the search for extraterrestrial intelligence. The signal appeared to come from the direction of the constellation Sagittarius and bore expected hallmarks of extraterrestrial origin."
- The Big Ear radio telescope and the Wow! signal, Dr. Jerry R. Ehman, Big Ear Radio Observatory (bigear.org)
- This mysterious radio signal has puzzled astronomers for nearly 50 years, National Geographic (2026)