In the early hours of August 15, 1977, the Big Ear radio telescope at Ohio State University recorded a narrowband radio signal far stronger than the background noise of the sky, at a frequency close to the 21 cm line of neutral hydrogen — historically one of the most promising bands for searches of artificial signals. The signal lasted 72 seconds, the exact time it took Earth's rotation to carry the instrument's beam across that point in the sky, and it appeared in only one of the telescope's two receiving channels, as would be expected from a real source rather than terrestrial interference. Days later, while reviewing the printed computer printout, astronomer Jerry Ehman circled the sequence "6EQUJ5" and wrote "Wow!" in the margin — the origin of the name by which the case is known. There has never been a second detection, despite decades of searches aimed at the same region of the sky with more sensitive instruments, and no raw data exists beyond that single printout.
What happened, in a few lines, with no interpretation built in.
Original Big Ear printout with the "Wow!" annotation
Printed output from the radio telescope's computer, showing the intensity sequence "6EQUJ5" and astronomer Jerry Ehman's handwritten note, captured in just 1 of the receiver's 50 channels.
Date: Aug 15, 1977 · Origin: Ohio State University Radio Observatory / North American AstroPhysical Observatory (NAAPO)
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1963–1998
Big Ear's period of operation, including the longest-running SETI program in history (1973–1995).
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Aug 15, 1977, early morning
Big Ear records the signal during an automated sky survey.
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A few days later
Jerry Ehman reviews the printed printout and writes "Wow!" in the margin.
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1977–today
Searches for a repeat of the signal in the same region of the sky find nothing equivalent.
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1998
Big Ear is dismantled after the land it stood on is sold.
All in the same field of evaluation. None wins by default.
Recent studies ("Arecibo Wow! I" and "Arecibo Wow! II", 2024–2025) propose a cold neutral-hydrogen cloud amplified by a rare transient event. This would explain the frequency, but neither paper has reached consensus in the scientific community.
Terrestrial interference was considered and partly ruled out: Big Ear had two receiving beams, and the signal appeared in only one, as would be expected from a real celestial source rather than local noise common to both beams.
A non-natural, technological origin is often cited, but no additional data (repetition, message structure, a second detection) supports it beyond the anomaly of the signal itself.
- The signal was never redetected, despite dozens of attempts with more sensitive instruments in the following decades.
- No audio recording or raw data exists beyond the printout — the analysis depends entirely on that single record.
- A real radio signal was recorded by the instrument on 08/15/1977, with an intensity profile consistent with a fixed source in the sky.
- The frequency was close to the 21 cm line of neutral hydrogen, of historical interest to SETI searches.
- The physical origin of the signal — natural, artificial or instrumental.
- Why it was never repeated, even with targeted searches.
- Additional raw data from the moment of detection, if it exists in any archive, has not yet been published.
- A second detection, at the same frequency and region of the sky, would be the single most informative piece of data possible.
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Documentaries, interviews and coverage about the case. A third-party video is not evidence of the case — it's context material.
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The Wow! Signal with Discoverer Dr. Jerry Ehman
Interview with astronomer Jerry Ehman, who discovered and annotated the Wow! signal on the original 1977 printout.
Watch on YouTube ↗- Primary source North American AstroPhysical Observatory (NAAPO) — Wow! signal archive
- Background reference Wow! signal — Wikipedia (EN)
- Academic paper Arecibo Wow! I (arXiv, 2024)
- Academic paper Arecibo Wow! II (arXiv, 2025)
- Contemporary press Astronomy.com — Aug. 15, 1977: The Wow! Signal arrives
- Later investigation Scientific American — The Wow! Signal SETI Mystery Might at Last Be Solved
An interview or podcast is listed here as a path to a claim, never as proof of the claim.
This case is the starting point of the novel SIGNAL/NOISE. What the plot imagines happened with the signal from there on is entirely fictional — see the book page for how the factual research relates to the fiction, with no spoilers here.
See the book page →