# The 1977 'Wow! signal' was a message from an alien civilization

**No verdict.** A genuinely strong, narrowband signal near the hydrogen line that has never repeated and has no accepted explanation. The leading natural candidates (a comet, a magnetar-triggered hydrogen cloud) remain unconfirmed, and so does the extraterrestrial one.

Category: UFOs & Aliens · Era: Cold War era · First circulated: 1977 · Believed by: widely cited as SETI's strongest unexplained candidate signal
URL: https://theconspiratory.com/theory/wow-signal

## Summary
A 72-second radio burst recorded by a university telescope near the frequency SETI researchers consider the most logical channel for interstellar hello: strong, narrowband, never repeated, and still without a confirmed explanation nearly fifty years later.

## The claim
That the Wow! signal, detected on August 15, 1977 by the Big Ear radio telescope at Ohio State University, was an intentional or naturally-leaked transmission from an extraterrestrial civilization, and that its unexplained nature is evidence that we briefly heard from one.

## Origin and timeline
- 1965–73: Ohio State University's 'Big Ear' telescope, a fixed Kraus-type radio observatory near Delaware, Ohio, completes a major sky survey and is repurposed as one of the world's first full-time dedicated SETI observatories.
- Aug 15, 1977: At 10:16 p.m. local time, Big Ear's automated receiver records a strong, narrowband signal lasting the full 72-second window the telescope could observe any fixed point, near 1420 MHz.
- a few days later: Reviewing the printouts, volunteer astronomer Jerry R. Ehman notices the anomaly, circles the intensity code '6EQUJ5' in red pen, and writes 'Wow!' in the margin, giving the signal its name.
- 1977–2002: Ehman, Robert Dixon, and other Ohio State researchers search the same coordinates repeatedly through 1977. Later, independent astronomers including Robert Gray run further searches with the Very Large Array and other instruments. None redetect it.
- 1994: Big Ear observatory director John Kraus and Ehman lay out the signal's known parameters and open questions in correspondence and public writing, emphasizing what could be ruled out rather than declaring an answer.
- 1998: Ehman publishes 'The Big Ear Wow! Signal: What We Know and Don't Know About It After 20 Years,' a firsthand technical accounting that remains the most-cited primary source on the event.
- 1998: Big Ear is dismantled to make way for a golf course expansion, ending the observatory's run before more sensitive re-searches could be attempted with the original instrument.
- 2016–17: Antonio Paris and Evan Davies propose that hydrogen gas surrounding comets 266P/Christensen and P/2008 Y2 (Gibbs), passing through the same patch of sky in 1977, could have produced the signal. Ohio SETI veterans publish a rebuttal disputing the timing and physics.
- 2020: Amateur astronomer Alberto Caballero identifies a sun-like star, 2MASS 19281982-2640123, in the signal's error region as a candidate host; radio searches in 2022 find no technosignature there and do not confirm it as the source.
- 2024: Researchers at the Arecibo Planetary Habitability Laboratory, reanalyzing archival 2020 Arecibo drift-scan data, propose that a transient event (such as a magnetar flare) striking a cold interstellar hydrogen cloud could produce a maser-like brightening resembling the Wow! signal.

## The evidence, claim by claim
- Claim: The signal was exactly the kind of transmission SETI theorists had predicted an alien civilization would send.
  Evidence: True as far as it goes: it was strong, narrowband, and close to the 1420 MHz hydrogen line, a frequency radio astronomers had specifically flagged since the 1959 Cocconi–Morrison paper as a plausible universal 'hailing channel.' That is exactly why Big Ear was listening there. But matching a prediction is not the same as confirming a transmitter; several natural processes also cluster near that frequency, which is precisely why it was chosen as a quiet, watched part of the spectrum.
- Claim: The signal was extremely strong and clearly not background noise.
  Evidence: Correct and undisputed. It reached roughly 30 times the background noise level, pinned the recording equipment, and Ehman himself called it unlike anything else the project had seen in years of data. Its strength is what makes the case notable rather than a routine glitch.
- Claim: The fact that it never repeated, despite decades of searching, means the signal was probably real and probably deliberate.
  Evidence: The lack of repetition is real and well-documented. Ohio State's own team, and independent researchers such as Robert Gray using the far more sensitive Very Large Array, searched the same coordinates for years and found nothing. But non-repetition cuts both ways: it is equally consistent with a one-off natural transient (a flare, a scintillation event, a brief brightening of a gas cloud) as with a civilization that, for unknown reasons, transmitted exactly once in this direction and never again.
- Claim: A comet has been scientifically proposed as the source, so this shows the signal was probably natural and mundane.
  Evidence: A peer-reviewed 2017 paper did propose exactly this, but it was disputed by the Ohio SETI researchers who built and ran Big Ear, who published data showing the named comets were not in the telescope's narrow beam at the right time and that comets are not known to emit narrowband hydrogen-line radiation this strongly. The comet hypothesis is a real, testable scientific claim, but a contested one, not a settled explanation.

## Why people believe it
- The signal genuinely fits, better than almost any other recorded anomaly, the specific technical profile SETI theorists said an alien beacon should have, which is a legitimate reason working scientists have taken it seriously for nearly fifty years.
- Its total, permanent non-repetition despite sustained professional search efforts denies any side a clean resolution, so the story never gets to end. It lives in the same evidentiary limbo that fuels the biggest true unsolved mysteries.
- A famous, almost theatrical detail, an astronomer circling a code and scrawling 'Wow!' in the margin, gives the story a human, visual hook that a drier technical footnote never would have gotten.
- SETI itself is built on the premise that a real signal must look exactly like this one did: brief, narrowband, and non-repeating, since a beacon or leaked transmission would not be expected to loop forever for our convenience.

## Open questions
- The signal has never been detected again, despite repeated searches of the same coordinates by the original Ohio State team through 1977, a more sensitive Very Large Array search by independent researcher Robert Gray in the 1990s, and later attempts by other observatories. Whether that permanent silence means the source was a one-time event, a transmitter that has since gone quiet or moved on, or a natural process too rare to repeat on a human timescale isn't something any search conducted so far can answer.
- Whether the signal's ultimate cause was extraterrestrial technology, a natural astrophysical event, or an unidentified form of interference remains genuinely undecided. Every specific version of each possibility proposed since 1977 (a deliberate transmission, a comet, a magnetar-triggered hydrogen cloud, a reflected terrestrial signal) has been disputed, left unconfirmed, or both, and no single account commands the field.
- The 2017 comet hypothesis was directly challenged, on both timing and physics grounds, by the Ohio SETI veterans who built and ran Big Ear, and its authors have not withdrawn it. Whether cometary hydrogen-line emission anywhere near the observed strength is even physically possible remains a live, if largely set-aside, scientific dispute rather than a settled question.
- The hydrogen-cloud hypothesis, most recently updated in an August 2025 reanalysis that revised the signal's measured strength and sky position, is, by its own authors' account, still an unreviewed body of work that identifies a plausible natural setting for the signal without identifying what actually triggered it. Whether a magnetar flare, a soft gamma repeater, or something else entirely occurred in that patch of sky in 1977, and whether that could ever be confirmed decades after the fact, remains unknown.

## Sources
- The Big Ear Wow! Signal: What We Know and Don't Know About It After 20 Years, Dr. Jerry R. Ehman, Ohio State University Radio Observatory (bigear.org) (1998): https://www.bigear.org/wow20th.htm
- Wow! Signal: 30th Anniversary Report, Dr. Jerry R. Ehman, Ohio State University Radio Observatory (bigear.org) (2007): https://www.bigear.org/Wow30th/wow30th.htm
- Rebuttal of the Claim that the 'Wow!' Signal Was Caused by a Comet, Dr. Robert S. Dixon, North American AstroPhysical Observatory (NAAPO): http://naapo.org/WOWCometRebuttal.html
- Hydrogen Clouds from Comets 266P/Christensen and P/2008 Y2 (Gibbs) are Candidates for the Source of the 1977 'Wow!' Signal, Antonio Paris & Evan Davies, Journal of the Washington Academy of Sciences (2017): https://arxiv.org/abs/1706.04642
- A VLA Search for the Ohio State 'Wow', Robert H. Gray & Kevin B. Marvel, The Astrophysical Journal, 546(2) (2001): https://iopscience.iop.org/article/10.1086/318308
- Arecibo Wow! I: An Astrophysical Explanation for the Wow! Signal, Abel Méndez, Kevin Ortiz Ceballos & Jorge I. Zuluaga, Planetary Habitability Laboratory, University of Puerto Rico at Arecibo (arXiv preprint) (2024): https://arxiv.org/abs/2408.08513
- Arecibo Wow! II: Revised Properties of the Wow! Signal from Archival Ohio SETI Data, Abel Méndez et al., Planetary Habitability Laboratory, University of Puerto Rico at Arecibo (arXiv preprint) (2025): https://arxiv.org/abs/2508.10657
- The Wow! Signal: New analysis closes in on mysterious source, EarthSky (2025): https://earthsky.org/space/the-wow-signal-seti-hydrogen-line-maser/
- Wow! signal, Wikipedia: https://en.wikipedia.org/wiki/Wow!_signal

Rated by The Conspiratory, a neutral, sourced encyclopedia of conspiracy theories. Full page: https://theconspiratory.com/theory/wow-signal