Was the Wow! signal a message from aliens?
The 1977 detection is real data and was never seen again. An alien sender is unverified, the comet explanation fails against NASA orbit data, and a natural hydrogen flare is a new, unconfirmed idea.
- ✓ Confirmed15 Aug 1977At about 11:16 pm, the telescope records a strong, narrow signal for 72 seconds
- UnverifiedTheoryThe signal was sent by an extraterrestrial intelligence
- ✕ DisprovenTheoryHydrogen around the two comets caused the Wow! signal
- UnverifiedTheoryThe Wow! was a natural flare in a hydrogen cloud
For 72 seconds in August 1977 an Ohio radio telescope picked up a strong, narrow signal near the frequency SETI searchers were watching. It has never been heard again.
The question What was the strong radio signal the Big Ear telescope recorded on 15 August 1977?
What the records say
The documented story holds up: 13 of 13 timeline steps are Confirmed by the records (score 100).
4 theories checked: 1 disproven, 3 unverified. A theory is rated by its key claim.
The Arecibo Wow! team proposes a natural flare and revises the signal’s properties
confirmedConfirmed as a record of what this document says, not that it is true. See the step
Down the rabbit hole
The ground line is the documented timeline. Each tunnel is a theory that branches off it; every chamber is a step, coloured by how well the records support it. The deepest chamber is the theory’s key claim. Tap one to open it.
Main timeline
Oldest first- 1973confirmed
Ohio State’s Big Ear telescope is turned to the search for alien signals
After losing its National Science Foundation funding in 1972, the observatory began a sky survey for narrowband radio signals, run largely by volunteers, Jerry Ehman and Bob Dixon among them.
- 15 Aug 1977confirmed
At about 11:16 pm, the telescope records a strong, narrow signal for 72 seconds
It appears in channel 2 of the printout as the sequence 6EQUJ5. At its peak, “U”, it was about 30 times stronger than the background noise.
T1Ehman’s 20-year report, 1997–98Introduction; Signal StrengthT1Gray and Marvel, ApJ, Jan 2001p. 1171 - Aug 1977confirmed
Days later, Jerry Ehman circles it and writes “Wow!”
Reviewing the printout a few days after the detection, he circled the six characters in red and wrote “Wow!” in the margin. NPR dates this to 18 August.
T1Ehman’s 20-year report, 1997–98IntroductionT2NPR, 28 May 2010 - 15 Aug 1977confirmed
The signal sat close to the hydrogen line, the frequency many searchers expected aliens to use
Ehman’s analysis gives 1420.4556 ± 0.005 MHz. The band around 1420 MHz is protected: no transmitter on Earth or in space should use it.
T1Ehman’s 20-year report, 1997–982nd L.O. Frequency; SatellitesT1Gray and Marvel, ApJ, Jan 2001p. 1171T2NPR, 28 May 2010Sources disagreeAn earlier figure from John Kraus, quoted by Gray and Marvel, is 1420.356 MHz; Ehman’s 1998 analysis gives 1420.4556 MHz; the 2025 Arecibo Wow! re-analysis gives 1420.726 ± 0.005 MHz. - 15 Aug 1977confirmed
It matched a source fixed in the sky, but showed up in only one of the telescope’s two beams
Gray and Marvel found the intensities fit the telescope’s antenna pattern very closely (r = 0.99). A fixed source should have appeared in both beams, minutes apart; this one appeared in one.
T1Gray and Marvel, ApJ, Jan 2001pp. 1171–1172T1Ehman’s 20-year report, 1997–98Intermittency, Duration, and Modulation - 1977–1980sconfirmed
It is never seen again
Ohio State made about 100 more scans at the same declination over the next few years without detecting it again.
T1Gray and Marvel, ApJ, Jan 2001p. 1171T2Columbus Dispatch, 18 Sep 1994editor’s note - 18 Sep 1994confirmed
Ehman tells a newspaper it may have been an Earth signal bounced off space debris
He told the Columbus Dispatch: “Something suggests it was an Earth-bound signal that simply got reflected off a piece of space debris.”
- 1995–1996confirmed
Gray and Marvel’s Very Large Array search finds nothing that could explain it
With over 100 times the original sensitivity they found no steady source that could have flared to produce it. They note their search “does not significantly constrain the possibility of intermittent sources”.
T1Gray and Marvel, ApJ, Jan 2001pp. 1171, 1173 - Feb 1998confirmed
Ehman concludes an alien intelligence “might have sent the signal”
His 20-year report says the Earthly explanations were “either ruled out or seem improbable”, and that “the origin of the Wow! signal is still an open question for me.”
- Jun 2017confirmed
Antonio Paris and Evan Davies propose two comets as the source
Their paper says hydrogen clouds around comets 266P/Christensen and P/2008 Y2 (Gibbs) “are strong candidates for the source of the 1977 Wow signal”.
T1⚠ QuestionedParis and Davies, comet paper, 2017abstract - May 2022confirmed
Alberto Caballero names a Sun-like star as a candidate source
Of 66 stars sampled in the Wow! region, his paper identifies one potential Sun-like star, 2MASS 19281982-2640123, as an ideal target for follow-up.
- 21 May 2022confirmed
The SETI Institute and Breakthrough Listen report no signal from that star
The Green Bank Telescope and the Allen Telescope Array observed it together; the observations “did not detect a technosignature candidate”.
- Aug 2024–Aug 2025confirmed
The Arecibo Wow! team proposes a natural flare and revises the signal’s properties
Its 2024 preprint suggests a sudden brightening of cold hydrogen clouds, triggered by something like a magnetar flare. Its 2025 preprint, using unpublished Ohio State data, gives a higher frequency and a peak above 250 Jy.
T3Arecibo Wow! I preprint, Aug 2024abstractT3Arecibo Wow! II preprint, Aug 2025abstract
Branches
Go down oneA branch is only as strong as its weakest step so far. The count is how many sources back each step.
An alien transmission
Was the Wow! signal sent by an extraterrestrial intelligence?
The Ohio SETI group went public about the signal in 1979 through Cosmic Search, its own magazine, as the Arecibo Wow! project’s history records. Ehman’s 1998 report gave the case for an alien source its fullest statement.
- 1,620,115 YouTube views of “The Wow! Signal After 45 Years” (Cool Worlds) as of 17 Oct 2026 T3YouTube: Cool Worlds, “After 45 Years”
- 505,813 YouTube views of “Brian Cox investigates a potential alien signal” (BBC) as of 17 Oct 2026 T3YouTube: BBC, Brian Cox
- 106,359 YouTube views of “The WOW Signal: Did Aliens Try to Contact Us?” (Best Documentary) as of 17 Oct 2026 T3YouTube: “Did Aliens Try to Contact Us?”
It came in near the hydrogen line, where searchers expected aliens to call
NPR: physicists Cocconi and Morrison had proposed looking for a signal at 1420 MHz, and this one was “just a smidge from where it was expected”.
The premise: confirmedTrue: Ehman puts it at 1420.4556 MHz, in a band protected from transmitters. A 2025 re-analysis puts it higher, at 1420.726 MHz, which is still near the line.
T1Ehman’s 20-year report, 1997–982nd L.O. FrequencyT3Arecibo Wow! II preprint, Aug 2025abstractEvery Earthly source was checked and ruled out
Ehman: “all of the possibilities of a terrestrial origin have been either ruled out or seem improbable”.
The premise: likelyThe team found no planet, large asteroid, known satellite or known spacecraft in the beam. Gray and Marvel still write that an interference origin “cannot be entirely ruled out”.
T1Ehman’s 20-year report, 1997–98Planets to SpacecraftT1Gray and Marvel, ApJ, Jan 2001p. 1172It behaved exactly like a source far out in space
Its rise and fall matched the telescope sweeping past a fixed point in the sky.
The premise: confirmedGray and Marvel found a fit of r = 0.99 and say this rules out ground-based transmitters. It does not say whether the source was natural or artificial.
T1Gray and Marvel, ApJ, Jan 2001p. 1172A Sun-like star lies in the right patch of sky
Caballero’s 2022 paper names one.
T1Caballero, Int. J. Astrobiology, 2022abstractThe premise: confirmedThe paper names 2MASS 19281982-2640123. A coordinated search of it in May 2022 found no technosignature.
- confirmed
The signal was strong, narrow, near the hydrogen line and fixed in the sky
Carried over from the main timeline (steps 2, 4 and 5).
T1Ehman’s 20-year report, 1997–98T1Gray and Marvel, ApJ, Jan 2001pp. 1171–1172StartStrength so far:confirmed· 2 sources on this step - confirmed
The man who found it says an alien intelligence might have sent it
Carried over from the main timeline (step 9).
= HoldsStrength so far:confirmed· 1 source on this step - confirmed
Every search since has come up empty
About 100 later Ohio State scans, the 1995–96 Very Large Array search and the 2022 Green Bank and Allen Telescope Array observations found nothing.
T1Gray and Marvel, ApJ, Jan 2001pp. 1171, 1173T2SETI Institute release on the 2022 search= HoldsStrength so far:confirmed· 2 sources on this step - unverified
Key claim: the signal was sent by an extraterrestrial intelligence
No record confirms it and none rules it out. The signal was seen once and never again, so it cannot be tested.
▼ WeakerStrength so far:unverified· 2 sources on this step
Bullshit meter
- Key claim: the signal was sent by an extraterrestrial intelligence. Unverified.
- Key claim contradicted by tier 1? Not by an independent record. No record confirms or rules out an artificial source; the signal was seen once.
Fluff meter: possibly planted
- Can’t be traced to an original record. Absent: the detection traces to the observatory’s original printout.
- First appeared from new or anonymous accounts. Absent: published by the observatory’s own named staff.
- Coordinated identical wording. Not measured.
- Cited source doesn’t exist. Absent.
- Later contradicted. Not measured.
● present · ○ absent · – not measured. Lists signals only. It never accuses anyone.
Personal interest meter
- None documented. With no sources attached there is no one to check.
“Has a documented interest” only, each one sourced. Never an implication of guilt.
Correlation meter
Links to other cases appear once those cases exist.
Who worked on this
This case was assembled by the site from public records. Contributions are not open yet. Nothing here is invented, so the counts are zero.
This is the first published version of the case.
Sources
- T1Jerry R. Ehman, “The Big Ear Wow! Signal: What We Know and Don’t Know About It After 20 Years”, Ohio State University Radio Observatory, draft of 1 Sep 1997, revised 3 Feb 1998 (the discoverer’s analysis of the observatory’s original printout). www.bigear.org
- T2Columbus Dispatch Sunday Magazine article on Jerry Ehman and the Wow! signal, 18 Sep 1994, as reprinted by the Ohio State University Radio Observatory. www.bigear.org
- T1Robert H. Gray and Kevin B. Marvel, “A VLA Search for the Ohio State ‘Wow’”, The Astrophysical Journal 546:1171–1177, 10 Jan 2001 (peer-reviewed). doi.org · copy read: www.bigear.org
- T2Robert Krulwich, “Aliens Found In Ohio? The ‘Wow!’ Signal”, NPR, 28 May 2010. www.npr.org
- T2Planetary Habitability Laboratory, University of Puerto Rico at Arecibo, “Arecibo Wow!” project page (history and results), as read on 17 Oct 2026. phl.upr.edu
- T1⚠ QuestionedNASA JPL’s current orbits put both comets more than 10 degrees from the Wow! position on the night, and the Ohio State observatory’s 1977 director said the comets were not in the telescope’s sight lines. Antonio Paris and Evan Davies, “Hydrogen Clouds from Comets 266P Christensen and P2008 Y2 (Gibbs) are Candidates for the Source of the 1977 WOW! Signal”, Journal of the Washington Academy of Sciences 101(4) (dated Winter 2015), posted to arXiv 14 Jun 2017 (abstract read). arxiv.org
- T1NASA Jet Propulsion Laboratory, Horizons system: geocentric astrometric positions of 266P/Christensen (solution JPL#K263/2) and 335P/Gibbs, formerly P/2008 Y2 (solution JPL#39), for 16 Aug 1977 03:00–04:00 UT, queried by us on 17 Oct 2026 (UTC). ssd.jpl.nasa.gov
- T3Statement by the staff of the Ohio State University Radio Observatory on the comet explanation, North American AstroPhysical Observatory website (undated). web.archive.org · copy read: naapo.org
- T2Eric Mack, “Aliens could still explain the ‘Wow signal,’ scientists say”, CNET, 14 Jun 2017. www.cnet.com
- T1Alberto Caballero, “An approximation to determine the source of the WOW! Signal”, International Journal of Astrobiology 21 (2022), p. 129 (arXiv:2011.06090; abstract read). www.cambridge.org · copy read: arxiv.org
- T2SETI Institute, “1st Coordinated Green Bank Telescope/Allen Telescope Array Observes Possible Source of the WOW! Signal” (on observations of 21 May 2022). www.seti.org
- T3Abel Méndez, Kevin Ortiz Ceballos and Jorge I. Zuluaga, “Arecibo Wow! I: An Astrophysical Explanation for the Wow! Signal”, arXiv:2408.08513, 16 Aug 2024 (preprint, submitted to ApJ; abstract read). arxiv.org
- T3Abel Méndez and ten co-authors, “Arecibo Wow! II: Revised Properties of the Wow! Signal from Archival Ohio SETI Data”, arXiv:2508.10657, 14 Aug 2025 (preprint; abstract read). arxiv.org
- T3“The Wow! Signal After 45 Years”, Cool Worlds (David Kipping), YouTube, 18 Jun 2022. www.youtube.com
- T3“Brian Cox investigates a potential alien signal”, BBC, YouTube, 17 Jun 2021. www.youtube.com
- T3“The WOW Signal: Did Aliens Try to Contact Us?”, Best Documentary, YouTube, 13 Aug 2025. www.youtube.com
- T3“The Wow Signal Potentially Explained ... and it’s Weird”, John Michael Godier, YouTube, 18 Aug 2024. www.youtube.com
- T3“We Were Wrong About the Wow! Signal - It Was Even More Bizarre”, Anton Petrov, YouTube, 28 Aug 2025. www.youtube.com