What Is the Wow Signal? The 1977 Space Mystery
Ohio State's Big Ear, a red-ink note, and why astronomers now suspect a hydrogen cloud.
Aditya Challa2 min read
Summary
What is the Wow signal? It is a strong, narrowband radio signal that Ohio State University's Big Ear radio telescope recorded on 15 August 1977 for about 72 seconds. Astronomer Jerry Ehman circled it on the printout and wrote "Wow!" beside it. It has never been detected again, and its source is still unconfirmed.
Why did the Wow signal look like an alien message?
The signal sat very close to 1420 MHz, the natural emission frequency of neutral hydrogen. Many SETI researchers had suggested that frequency as a logical channel for a civilisation trying to be noticed. The burst was also very narrow in frequency and around 30 times stronger than the background noise, unlike most natural sources known at the time.
What does 6EQUJ5 mean?
The Big Ear computer printed signal strength as numbers and letters. The sequence 6EQUJ5 shows the intensity rising and falling as Earth's rotation swept the telescope's beam across the source. The "U" is the peak.
What do scientists think the Wow signal was?
In 2024, Abel Méndez and colleagues proposed a natural explanation: a cold cloud of hydrogen that briefly brightened like a laser, possibly after a flare from a magnetar or similar source. Their search of Arecibo Observatory archive data found fainter signals with a similar look. A 2025 reanalysis of the original Ohio data refined the frequency and duration and was consistent with that idea. It remains a hypothesis, not a confirmed answer.
Has anyone found the Wow signal again?
No. Repeated searches of the same region of sky in Sagittarius have found nothing matching it.
FAQ
Was the Wow signal aliens? There is no evidence that it was. Researchers now favour natural explanations, but the case is not closed.
Where did the Wow signal come from? The direction of the constellation Sagittarius.
Can you see the original printout? Yes. Copies of Ehman's annotated printout are widely reproduced, including on SETI-related sites.
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Sources
Lab evidence
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Facts in this draft were checked on 14 Oct 2026 against the sources listed in the body (official records, publishers, encyclopaedias, research papers and named news outlets). No original testing or reporting was done; figures are quoted as published by those sources, fiction and folklore are labelled as such, and any estimate or prediction is labelled as such.
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