Arecibo Wow! is a search for transient radio signals inspired by the Wow! Signal

For a review of transient radio astronomy see Murphy & Kaplan (2025)

A Brief History of the Wow! Signal

The Ohio State University Radio Observatory (OSURO, 1963–1998) — better known as “Big Ear” — was, in the early 1960s, the third-largest radio telescope in the United States, after the Arecibo Observatory (1963–2020) and the NRAO 300-foot telescope (1962-1998).

Big Ear’s primary mission was to scan the sky for new radio sources as part of the Ohio Sky Survey (OSS), conducted between 1965 and 1971. It cataloged nearly 20,000 radio sources, including what was then the most distant known object in the universe.

The telescope was designed and built by the renowned radio astronomer John Kraus of Ohio State University (OSU). Kraus also invented the helical antenna — now widely used in communication systems — and authored several influential books, including the classic Radio Astronomy textbook.

In 1972, Big Ear lost its National Science Foundation (NSF) funding. The NSF was shifting focus toward national facilities and away from university-managed telescopes. Many similar research projects across the country faced the same fate.

After NASA’s Project Cyclops in 1971 renewed excitement about the Search for Extraterrestrial Intelligence (SETI), staff astronomer Robert Dixon suggested repurposing the now-defunded Big Ear for SETI observations. John Kraus agreed.

Thus, in 1973, the Ohio SETI Project was born. Another staff astronomer, Jerry Ehman, joined the effort. Kraus remained as an astronomer at OSU, but Robert Dixon and Jerry Ehman soon had to find other full-time jobs, operating the telescope primarily in their spare time.

The Ohio SETI Project survived thanks to volunteers and students, with occasional donations and NASA and NSF small grants for equipment upgrades. OSU covered the telescope’s basic operational costs, but there was no funding for salaries.

Four years into the project, Jerry Ehman spotted a remarkable signal in the data — one that matched all the characteristics they were searching for in an extraterrestrial transmission. Astonished, he circled the data and wrote “Wow!” beside it, giving the famous Wow! Signal its name.

John Kraus and Robert Dixon immediately began deeper analyses, improving the telescope’s software and repeatedly reobserving the same region of sky. Despite years of follow-up, the signal was never detected again.

In 1979, the Ohio SETI group went public about the Wow! Signal through Cosmic Search, their own magazine — the first ever dedicated to the search for extraterrestrial life. It featured both introductory and technical articles, including by prominent astronomers such as Frank Drake, Carl Sagan, and Jill Tarter.

Interest in explaining the Wow! Signal persisted, but surprisingly few attempts were made to search for it again. One notable exception was Robert Gray, a data analyst from Chicago, who became fascinated with the signal in the early 1980s. He first tried observing it with a homemade radio dish, and later with several professional radio telescopes, but it never repeated.

The Big Ear holds the record for the longest-running dedicated SETI project, operating for 24 years (1973–1997). Other long-duration efforts include SETI@Home, which ran for 21 years (1999–2020); the META/BETA search at Harvard, active for about 15 years (1985–2000); and Project Phoenix, which operated for 9 years (1995–2004).

Although SETI projects began as early as 1960 with Frank Drake’s Project Ozma, it was Big Ear, ironically the least funded of them all, that detected the most intriguing SETI signal ever recorded. A major reason may be that the Ohio SETI program devoted 100% of the telescope’s time to a continuous all-sky survey, while other SETI efforts are limited to less telescope time and therefore can search only a much smaller portion of the sky.

Nearly 50 years later, the Arecibo Wow! Project was launched to search archived radio-telescope data — including from Arecibo — for Wow-like signals. To their surprise, the team uncovered a promising astrophysical explanation and found that the signal’s true characteristics differed slightly from early estimates, which may explain why it remained so elusive.

Today, the Arecibo Wow! Project brings together scientists from the Arecibo Observatory, surviving members of the Big Ear team, and astronomers who have long studied the Wow! Signal. We now understand much more about this enigmatic event — and may be closer than ever to finally solving a mystery that has captivated generations.

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