# The Wow! signal > On the night of 15 August 1977 the Ohio State University "Big Ear" radio telescope recorded a 72-second narrowband signal near the hydrogen line, about… Source: https://mysteriesdept.com/mysteries/wow-signal Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) Updated: 2026-10-27T17:48:32+00:00 --- **MYS** 0CXZ4FH21272·Mystery · signal # The Wow! signal **0** [Follow][Ask a question](https://mysteriesdept.com/questions/key-questions?mystery=wow-signal) The Wow! signal ![A scan of a color copy of the original computer printout, taken several years after the 1977 arrival of the Wow!](https://mysteriesdept.com/media/folio/wow-signal-lead) Big Ear Radio Observatory and North American AstroPhysical Observatory · Public domain Detected 15 August 1977, about 23:16 EDT (16 August 03:16 UTC)⁠[[2]] Telescope Ohio State University Radio Observatory (Big Ear), Delaware, Ohio⁠[[2]] Frequency 1420.4556 ± 0.005 MHz as recorded; 1420.726 MHz in the 2025 reanalysis⁠[[9]] Duration About 72 seconds (six 12-second integrations), the time a fixed source takes to cross the beam⁠[[2]] Intensity Peak about 30 times the noise; 54 or 212 Jy depending on the horn⁠[[2]] Position RA 19h25m31s or 19h28m22s, Dec −26°57′ (J2000); the horn is unknown⁠[[2]] Repeats None, in about a hundred follow-up observations 1977–2020⁠[[1]] Printout Held by the Ohio History Connection, Columbus⁠[[2]] Status Unexplained Questions 0 of 4 answered People [**Jerry R. Ehman** Volunteer astronomer at Big Ear who found and named the signal](https://mysteriesdept.com/mysteries/wow-signal/people/FIG0CXZ4GZY40AA/jerry-r-ehman)[**Robert H. Gray** Independent astronomer; led most follow-up searches](https://mysteriesdept.com/mysteries/wow-signal/people/FIG0CXZ4HQC3BV4/robert-h-gray)[**Abel Méndez** Planetary Habitability Laboratory, UPR Arecibo; leads the Arecibo Wow! project](https://mysteriesdept.com/mysteries/wow-signal/people/FIG0CXZ4J707PQ3/abel-mendez)[**Robert S. Dixon** Director of the Ohio SETI programme](https://mysteriesdept.com/mysteries/wow-signal/people/FIG0CXZ4H7R3Y37/robert-s-dixon)[**John D. Kraus** Designer and builder of the Big Ear](https://mysteriesdept.com/mysteries/wow-signal/people/FIG0CXZ4HFJ5WGG/john-d-kraus) All 7 people › [**Antonio Paris** Proposed the comet hypothesis](https://mysteriesdept.com/mysteries/wow-signal/people/FIG0CXZ4HZ65CYQ/antonio-paris)[**David Kipping** Columbia University astronomer; repeating-beacon analysis](https://mysteriesdept.com/mysteries/wow-signal/people/FIG0CXZ4JET1H4X/david-kipping) Catalog key**MYS** 0CXZ4FH21272 The Big Ear was a Kraus-type radio telescope at Ohio State University's radio observatory near Delaware, Ohio: a tiltable flat reflector facing a fixed paraboloid, with two feed horns at the focus. It did not track; the sky drifted through its beam as the Earth turned, and from 1973 it ran the longest continuous search for extraterrestrial radio signals yet undertaken, scanning the hydrogen line in 50 channels of 10 kHz each⁠[[1]]⁠[[2]]. Each channel's intensity was integrated for 10 seconds, processed for 2, and printed as a single character: a digit for 1 to 9 standard deviations above the noise, then letters from A upward⁠[[2]]. A few days after 15 August 1977 the volunteer astronomer Jerry Ehman, reviewing the printout at home, saw the sequence 6EQUJ5 in channel 2: a rise to about 30 sigma and fall over six integrations, exactly the shape a point source makes drifting across the beam, in a band no wider than 10 kHz near the protected hydrogen frequency⁠[[2]]. He circled it and wrote "Wow!" in the margin. The signal appeared in only one of the two horns, which look at the sky about three minutes apart in right ascension, so it was either switched off within three minutes or was never on when the second horn arrived; and it left the position ambiguous between two points about three minutes apart⁠[[2]]. The telescope re-observed the position repeatedly and saw nothing; neither did Robert Gray with a 12-metre dish and later the Very Large Array, nor the META receiver at Harvard, nor the Hobart telescope in Tasmania over fourteen hours of continuous monitoring⁠[[3]]⁠[[4]]⁠[[5]]. What it was not is clearer than what it was. Its narrow bandwidth rules out natural thermal emission, which is broad; its frequency lies in a band reserved for radio astronomy, where transmitters are forbidden; its duration and shape fit a source fixed on the sky, not an aircraft or satellite passing through the beam⁠[[2]]. A reflection of a terrestrial signal from space debris cannot be excluded by the data alone but requires a transmitter breaking the protected band⁠[[2]]. A 2015–2017 proposal that two comets were the source was rejected by the Big Ear staff on position, physics and beam-width grounds⁠[[6]]⁠[[7]]. In 2024 Abel Méndez and colleagues, using archived Arecibo observations, proposed that the signal was a sudden maser-like brightening of a small cold hydrogen cloud, perhaps triggered by a magnetar flare; a 2025 reanalysis of the Big Ear archive by the same group narrowed the position, raised the flux and shifted the frequency, and argued for an astrophysical rather than terrestrial origin⁠[[8]]⁠[[9]]. The proposal is a hypothesis awaiting a second example. Of the 4 questions on this site, 0 are answered. The most likely answer to “Has the signal ever repeated, and what would a search need to find out?”, not yet confirmed: the source does not repeat on any timescale sampled so far (seconds to decades). ### Key questionsset by the editors [**Has the signal ever repeated, and what would a search need to find out?** ](https://mysteriesdept.com/mysteries/wow-signal/questions/QST0CXZ4PKM6DRS/has-the-signal-ever-repeated-and-what-would-a-search-need-to)Most likely: the source does not repeat on any timescale sampled so far (seconds to decades) [**What produced the Wow! signal?** ](https://mysteriesdept.com/mysteries/wow-signal/questions/QST0CXZ4P403VSY/what-produced-the-wow-signal)No answer ahead yet [All 4 questions ](https://mysteriesdept.com/questions/key-questions?mystery=wow-signal) ## What happened The Ohio State University Radio Observatory was built by John Kraus between 1956 and 1963 and used for the Ohio Sky Survey until 1971; from 1973 it was given over to SETI, a programme led by Robert Dixon that ran until the telescope was demolished in 1998 to make way for a golf course and housing⁠[[1]]⁠[[2]]. The receiver recorded 50 channels of 10 kHz across the hydrogen line at 1420 MHz and the output went to an IBM 1130 computer and a line printer; the paper was collected every few days and delivered to Ehman for review⁠[[2]]. The signal entered the receiver at about 23:16 Eastern Daylight Time on 15 August 1977⁠[[2]]. Ehman's own 1997 and 2010 reports give the recorded parameters: observing frequency 1420.4556 ± 0.005 MHz in channel 2; a peak at about 30 sigma; a flux density inside the 10 kHz band of either 54 or 212 Jy, depending on which horn saw it; six data points at 12-second intervals, so about 72 seconds in all; and two possible J2000 positions, RA 19h25m31s ± 10s or 19h28m22s ± 10s, both at Dec −26°57′ ± 20′, in Sagittarius⁠[[2]]. The intensity profile matched the antenna pattern of a point source drifting through the beam within measurement error⁠[[2]]. [![The Wow! printout](https://mysteriesdept.com/files/v/91010da49dea8bed7e276c7ded362ce096bb7c9fbe31a8390f0e73220b9bd8bb/w800)](https://mysteriesdept.com/mysteries/wow-signal/artifacts/ART0CXZ50KY2WEN/the-wow-printout) The Wow! printoutMaxrossomachin, 1977. CC BY-SA 4.0[Artifact ](https://mysteriesdept.com/mysteries/wow-signal/artifacts/ART0CXZ50KY2WEN/the-wow-printout) The telescope's two horns produce a positive and a negative response offset by about 2 minutes 52 seconds in right ascension; a steady source produces both. The Wow! signal produced one. Either the source turned off (or on) within three minutes, or something blocked it in one horn; the staff could not say which horn saw it, and later checks of the horn wiring did not resolve the question⁠[[2]]. The Big Ear went on to log more than 40,000 transient narrowband events in 25 years of SETI operation; none has the Wow! signal's combination of strength and shape⁠[[1]]. **Map of the country** [Open the full map](https://mysteriesdept.com/mysteries/wow-signal/map) [Country][World] [+][−] 1 **Ohio State University Radio Observatory (Big Ear), Delaware, Ohio** Radio telescope (demolished 1998) Within 100 m 2 **Oak Ridge Observatory, Harvard, Massachusetts** Radio telescope (Harvard–Smithsonian 25.6 m dish, Project META) Within 100 m 3 **Very Large Array, New Mexico** Radio telescope Within 1 km MappedWithin 1 kmNatural Earth ### Timeline **Timeline** Squeezed where little happened. Each mark is a published claim, by how it stands:AcceptedMost likelyStill possibleDisputedRuled out ## The accounts There are no eyewitnesses in the ordinary sense; the record is the printout. Ehman's account of finding it a few days after the detection, probably on 19 August, is given in his own words in the 20th and 30th anniversary reports, which also reconstruct every number on the printout line by line⁠[[10]]⁠[[2]]. Dixon, the programme's director, and the chief observer Russell Childers have described the observatory's operation and the signal's place in it in a 2026 conference paper with Méndez⁠[[1]]. The original printout, which Ehman kept and annotated, is held by the Ohio History Connection in Columbus; a colour copy scanned several years after 1977 appears in Ehman's reports⁠[[2]]. ## What was recorded The printed record is six characters in one channel of one scan, with the surrounding noise. The Ohio SETI archive is larger than that: the programme digitised more than two million punch cards and magnetic tapes in the 1990s, covering about 70 per cent of the radio sky with a consistent setup over 25 years, and most of it has never been analysed⁠[[1]]. The Arecibo Wow! project began cataloguing and re-analysing the archive in 2024 and used it in 2025 to revise the signal's parameters: a position in one of two adjacent fields at RA 19h25m02s ± 3s or 19h27m55s ± 3s, Dec −26°57′ ± 20′; a peak flux above 250 Jy; and a frequency of 1420.726 ± 0.005 MHz, implying a Galactic source with a larger radial velocity than earlier work assumed⁠[[9]]. [![The Wow! printout](https://mysteriesdept.com/files/v/91010da49dea8bed7e276c7ded362ce096bb7c9fbe31a8390f0e73220b9bd8bb/w800)](https://mysteriesdept.com/mysteries/wow-signal/artifacts/ART0CXZ50KY2WEN/the-wow-printout) The Wow! printoutMaxrossomachin, 1977. CC BY-SA 4.0[Artifact ](https://mysteriesdept.com/mysteries/wow-signal/artifacts/ART0CXZ50KY2WEN/the-wow-printout) Follow-up observations are the other half of the record. Gray searched the two positions with a 12-metre telescope in 1987 and 1989 and found nothing⁠[[3]]. Gray and Kevin Marvel used the Very Large Array in 1995 and 1996, far more sensitive than Big Ear, and found no source above a few millijanskys at either position⁠[[4]]. Gray and Simon Ellingsen monitored the positions for 14 hours with the 26-metre Hobart telescope in 1998 and 1999, looking for a periodic source; nothing appeared⁠[[5]]. Big Ear itself looked many times. The 2026 paper counts about a hundred follow-up observations in all⁠[[1]]. Two later analyses bear on what a repeat would need. Earlier work had excluded a strictly periodic source with periods under about 40 hours. David Kipping and Gray showed in 2022 that a source repeating at random intervals is still compatible with the Big Ear logs, that 192 hours of later observations from META, Hobart and the Allen Telescope Array put the hypothesis in tension with the data at only 2.4 sigma, and that about 62 days of further observation would be needed to exclude it at 3 sigma⁠[[11]]. Alberto Caballero in 2022 proposed a Sun-like star in the Gaia catalogue, 2MASS 19281982−2640123, as a candidate origin, a suggestion that depends on the horn and the assumption of a stellar source⁠[[12]]. ## The explanations Terrestrial interference is the default for any single narrowband event and must be considered first. Against it: the frequency lies in a band where transmission is prohibited worldwide; the signal's rise and fall matched the beam pattern of a fixed point in the sky; aircraft and satellites cross the beam too fast or too slowly to produce that profile⁠[[2]]. For it: nothing in the data proves the signal was not a reflection of a ground transmitter from a piece of debris that happened to drift at the sidereal rate; Ehman regarded this as unlikely but not excluded⁠[[2]]. The 2025 reanalysis argues from the frequency shift that an astrophysical origin is more likely than interference⁠[[9]]. The comet hypothesis of Antonio Paris proposed that hydrogen clouds around comets 266P/Christensen and P/2008 Y2 (Gibbs), which were in the general region in 1977, produced the emission⁠[[6]]. Ehman and Dixon rejected it: the comets were off the recorded position by about an hour of right ascension (266P) or three degrees of declination (P/2008 Y2) against a beam three minutes wide in RA; a cometary hydrogen cloud would be degrees across while the signal came from a point; there is no known mechanism for strong 21-cm emission from comets; and a comet would have been seen in both horns⁠[[7]]. The hypothesis is not accepted by the Big Ear staff or by later analysts⁠[[8]]. The hydrogen-cloud hypothesis of Méndez, Ortiz Ceballos and Zuluaga rests on Arecibo drift scans from 2020 that found several narrowband signals near the hydrogen line, about a hundred times weaker than the Wow! signal, which they identify as small cold hydrogen clouds (kinetic temperature under about 100 K). They propose that the Wow! signal was such a cloud brightening suddenly, by stimulated emission or Dicke superradiance, after a burst of radiation from a transient such as a magnetar flare behind it⁠[[8]]. The mechanism would explain the narrow band, the hydrogen frequency, the single appearance and the point-like source. It does not yet have a second example, and the triggering transient was not observed; the authors say so⁠[[8]]. The 2025 revision of the frequency to 1420.726 MHz is consistent with the proposal and with a Galactic source⁠[[9]]. The extraterrestrial-transmitter hypothesis is the one the search was built to test. The signal has every property the Ohio programme expected an artificial beacon to have: narrow band, at the hydrogen line, fixed on the sky, strong⁠[[2]]. What it lacks is a repeat. A beacon that sweeps or repeats at intervals longer than the follow-ups cannot be excluded by the observations so far⁠[[11]]. No modulation or information content was recorded, because the receiver could not have recorded any⁠[[2]]. ### Published claims **Published claims and their status** | Year | Who | Claimed | Status | Reason | |---|---|---|---|---| | 1994 | Robert Gray⁠[3] | Searches of the two Wow! positions with a 12-metre telescope in 1987 and 1989 found no intermittent signal. | Accepted | Far more sensitive searches with the Very Large Array and the Hobart telescope also found nothing⁠[4]⁠[5]. | | 1998 | Jerry Ehman⁠[10] | The signal had every property expected of an extraterrestrial transmission, and no terrestrial or natural source has been found to fit it. | Still possible | It has not repeated in about a hundred follow-up observations, but a beacon repeating at long or random intervals has not been excluded⁠[1]⁠[11]. | | 2001 | Robert Gray and Kevin Marvel⁠[4] | Very Large Array observations in 1995 and 1996 show no source above a few millijanskys at either Wow! position. | Accepted | Fourteen hours of monitoring at Hobart and later observations also found nothing⁠[5]⁠[11]. | | 2002 | Robert Gray and Simon Ellingsen⁠[5] | Fourteen hours of monitoring the Wow! positions with the Hobart telescope found no periodic emission. | Accepted | The result stands, though a source repeating at random intervals is still compatible with all the follow-ups⁠[11]. | | 2010 | Jerry Ehman⁠[2] | A terrestrial signal reflected from space debris is unlikely, because it would need a transmitter in a protected band, but cannot be ruled out. | Still possible | The 2025 reanalysis argues from the revised frequency for an astrophysical origin, but the data cannot exclude a reflection⁠[9]. | | 2015 | Antonio Paris and Evan Davies⁠[6] | Hydrogen clouds around comets 266P/Christensen and P/2008 Y2 (Gibbs), then in the region, produced the signal. | Ruled out | The comets were about an hour of right ascension or three degrees of declination from a position fixed to within minutes, and a comet would have shown in both horns⁠[7]. | | 2017 | Robert Dixon and Jerry Ehman⁠[7] | The comet hypothesis fails on position, on the size of a cometary hydrogen cloud, on the lack of a 21-cm emission mechanism and on the single-horn detection. | Accepted | Later analysts have not taken up the comet hypothesis⁠[8]. | | 2022 | David Kipping and Robert Gray⁠[11] | A beacon repeating at random intervals is still compatible with all follow-up observations, and about 62 more days of watching would be needed to exclude it. | Still possible | The observations it calls for have not been reported, so the question it poses is still open⁠[1]. | | 2022 | Alberto Caballero⁠[12] | The Sun-like star 2MASS 19281982−2640123 is the most likely origin if the signal came from a star. | Still possible | It depends on which horn saw the signal and on a stellar source, and the 2025 reanalysis revised the position⁠[9]. | | 2024 | Abel Méndez, Kevin Ortiz Ceballos and Jorge Zuluaga⁠[8] | The signal was a sudden maser-like brightening of a small cold hydrogen cloud, triggered by a transient such as a magnetar flare. | Still possible | No second event has been seen and the triggering transient was not observed, as the authors note⁠[8]. | | 2025 | Abel Méndez and colleagues⁠[9] | Reanalysis of the Big Ear archive puts the signal at 1420.726 MHz with a peak flux above 250 Jy, which points to an astrophysical rather than terrestrial source. | Most likely | It improves on the 1977 parameters from the full archive, but it is one group's analysis and has not been repeated independently⁠[1]. | ## What would settle it A repeat would settle most of it. A second detection at the same position and frequency, with a modern receiver recording the waveform, would distinguish a hydrogen-cloud flare (a broadened, thermal line with no structure) from a transmitter (a spectral line narrower than any natural process, or modulation). The repeating-beacon analysis says what that costs: about 62 days of accumulated observation on the two positions to exclude a random repeater at 3 sigma⁠[[11]]. A second signal of the Wow! type anywhere on the sky, caught with a telescope able to follow up within minutes, would test the Méndez mechanism, which predicts that such events are rare but not unique and that they sit on cold hydrogen clouds⁠[[8]]. Short of a repeat, the Ohio archive is the one unexamined resource: 25 years of consistent data in which the signal's statistical company has never been fully characterised⁠[[1]]. ## Questions 0 of 4 questions are answered. **Key questions** [All 4](https://mysteriesdept.com/questions/key-questions?mystery=wow-signal) **0** [Has the signal ever repeated, and what would a search need to find out?](https://mysteriesdept.com/mysteries/wow-signal/questions/QST0CXZ4PKM6DRS/has-the-signal-ever-repeated-and-what-would-a-search-need-to) 0 of 0 sub-questions answered·0 Most likely: the source does not repeat on any timescale sampled so far (seconds to decades) **0** [What produced the Wow! signal?](https://mysteriesdept.com/mysteries/wow-signal/questions/QST0CXZ4P403VSY/what-produced-the-wow-signal) 0 of 2 sub-questions answered·0 Open: 5 answers, none ahead ## Evidence 22 findings [What produced the Wow! signal?](https://mysteriesdept.com/mysteries/wow-signal/questions/QST0CXZ4P403VSY/what-produced-the-wow-signal)16 findings [Terrestrial radio interference, direct or reflected from space debris, that happened to mimic a drifting…](https://mysteriesdept.com/mysteries/wow-signal/answers/ANS0CXZ4Q387T0X/terrestrial-radio-interference-direct-or-reflected-from)Still possible +[Nothing in the data excludes a reflection from debris moving at the sidereal rate; Ehman regarded it as unlikely but possible.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4R2G2F70/nothing-in-the-data-excludes-a-reflection-from-debris-moving)Speculative +[Single narrowband events were common at Big Ear, with more than 40,000 logged.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4RAA092D/single-narrowband-events-were-common-at-big-ear-with-more)Supported −[The frequency lies in a band where transmission is prohibited worldwide.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4QB21HGJ/the-frequency-lies-in-a-band-where-transmission-is)Established −[The intensity profile matched the beam pattern of a fixed point source within error.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4QJW0EPN/the-intensity-profile-matched-the-beam-pattern-of-a-fixed)Established −[The 2025 reanalysis finds a frequency shift consistent with a Galactic source and argues interference is less likely.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4QTP6316/the-2025-reanalysis-finds-a-frequency-shift-consistent-with)Suggestive [Hydrogen emission from comets 266P/Christensen or P/2008 Y2 (Gibbs) passing through the region.](https://mysteriesdept.com/mysteries/wow-signal/answers/ANS0CXZ4RJ42P8E/hydrogen-emission-from-comets-266p-christensen-or-p-2008-y2)Disputed −[In 1977 the comets were about an hour of right ascension and three degrees of declination from the position, against a beam three minutes wide.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4RSY0CPP/in-1977-the-comets-were-about-an-hour-of-right-ascension-and)Established −[No mechanism for strong cometary 21-cm emission is known; a cometary hydrogen cloud would be degrees across, not point-like.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4S1R0ZDZ/no-mechanism-for-strong-cometary-21-cm-emission-is-known-a)Supported −[A comet would have appeared in both horns; the signal appeared in one.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4S9J2YQA/a-comet-would-have-appeared-in-both-horns-the-signal)Established [A sudden maser-like or superradiant brightening of a small cold interstellar hydrogen cloud, triggered by a…](https://mysteriesdept.com/mysteries/wow-signal/answers/ANS0CXZ4SHC7DZM/a-sudden-maser-like-or-superradiant-brightening-of-a-small)Still possible +[Arecibo drift scans found narrowband hydrogen-line signals from small cold clouds, about a hundred times weaker than Wow!, in several fields.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4SS641MV/arecibo-drift-scans-found-narrowband-hydrogen-line-signals)Supported +[The revised frequency of 1420.726 MHz implies a Galactic source with a larger radial velocity.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4T103TMC/the-revised-frequency-of-1420-726-mhz-implies-a-galactic)Suggestive −[No triggering transient was observed in 1977 and no second example of such a flare has been recorded.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4T8T7FRW/no-triggering-transient-was-observed-in-1977-and-no-second)Established −[A maser flare would need hydrogen densities about a thousand times those of diffuse clouds; the authors therefore favour superradiance, which is untested at this scale.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4TGM3QAK/a-maser-flare-would-need-hydrogen-densities-about-a-thousand)Suggestive [A narrowband transmission from an extraterrestrial source, either a one-off or a beacon that repeats or…](https://mysteriesdept.com/mysteries/wow-signal/answers/ANS0CXZ4TRE5DTD/a-narrowband-transmission-from-an-extraterrestrial-source)Still possible +[Narrow band, hydrogen frequency, fixed on the sky, strong: every property the programme expected of a beacon.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4V081AF8/narrow-band-hydrogen-frequency-fixed-on-the-sky-strong-every)Supported +[A randomly repeating source is in only 2.4-sigma tension with all data so far.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4VFW6BHD/a-randomly-repeating-source-is-in-only-2-4-sigma-tension)Suggestive −[About a hundred follow-ups, including VLA, META and 14 hours at Hobart, found nothing.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4V826XPP/about-a-hundred-follow-ups-including-vla-meta-and-14-hours)Established −[No modulation or content was or could have been recorded by a 10 kHz, 12-second receiver.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4VQP1S0S/no-modulation-or-content-was-or-could-have-been-recorded-by)Established [Which horn saw it, and what does the single-horn detection mean?](https://mysteriesdept.com/mysteries/wow-signal/questions/QST0CXZ4PBT6QN1/which-horn-saw-it-and-what-does-the-single-horn-detection)1 finding [The positive (east) horn saw it; the source is at RA 19h25m.](https://mysteriesdept.com/mysteries/wow-signal/answers/ANS0CXZ4W7A5HDS/the-positive-east-horn-saw-it-the-source-is-at-ra-19h25m)Still possible +[The 2025 reanalysis narrows the two fields to RA 19h25m02s or 19h27m55s but cannot choose between them.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4WF44ZPD/the-2025-reanalysis-narrows-the-two-fields-to-ra-19h25m02s)Suggestive [Has the signal ever repeated, and what would a search need to find out?](https://mysteriesdept.com/mysteries/wow-signal/questions/QST0CXZ4PKM6DRS/has-the-signal-ever-repeated-and-what-would-a-search-need-to)3 findings [The source does not repeat on any timescale sampled so far (seconds to decades).](https://mysteriesdept.com/mysteries/wow-signal/answers/ANS0CXZ4X6J08DT/the-source-does-not-repeat-on-any-timescale-sampled-so-far)Most likely +[About a hundred follow-ups over four decades, including the VLA, META and Hobart, found no signal.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4XEC4X1R/about-a-hundred-follow-ups-over-four-decades-including-the)Established +[Strictly periodic sources with periods under about 40 hours are excluded.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4XP66F0B/strictly-periodic-sources-with-periods-under-about-40-hours)Supported [The source repeats on a schedule the follow-ups have not sampled (random repeater or long period).](https://mysteriesdept.com/mysteries/wow-signal/answers/ANS0CXZ4XY06E0W/the-source-repeats-on-a-schedule-the-follow-ups-have-not)Still possible +[A stochastic repeater is compatible with the Big Ear logs and only in 2.4-sigma tension with 192 hours of later data.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4Y5T6MZT/a-stochastic-repeater-is-compatible-with-the-big-ear-logs)Supported [What does the rest of the Ohio SETI archive say about the signal's statistical company?](https://mysteriesdept.com/mysteries/wow-signal/questions/QST0CXZ4PVE087H/what-does-the-rest-of-the-ohio-seti-archive-say-about-the)2 findings [The Wow! signal is unique in the archive in strength and shape.](https://mysteriesdept.com/mysteries/wow-signal/answers/ANS0CXZ4YNE1VYM/the-wow-signal-is-unique-in-the-archive-in-strength-and)Most likely +[The programme's own staff describe it as the only event of its kind in 25 years.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4YX87JYH/the-programmes-own-staff-describe-it-as-the-only-event-of)Supported [It is the brightest of a population of similar transients, natural or interference, recorded by the telescope.](https://mysteriesdept.com/mysteries/wow-signal/answers/ANS0CXZ4Z525NR8/it-is-the-brightest-of-a-population-of-similar-transients)Still possible +[The 2025 reanalysis used previously unpublished archive data and found that cold hydrogen clouds produce similar narrowband signals.](https://mysteriesdept.com/mysteries/wow-signal/evidence/EVD0CXZ4ZCW2EQG/the-2025-reanalysis-used-previously-unpublished-archive-data)Suggestive ## Artifacts The films, photos, papers and objects this mystery rests on, each with its own key and its distance from the original. **Artifacts** [See all 12](https://mysteriesdept.com/mysteries/wow-signal/artifacts) Photo1 step from object [The Wow! printout](https://mysteriesdept.com/mysteries/wow-signal/artifacts/ART0CXZ50KY2WEN/the-wow-printout) Big Ear Radio Observatory and North American AstroPhysical Observatory · Public domain Photo1 step from object [The Big Ear radio telescope](https://mysteriesdept.com/mysteries/wow-signal/artifacts/ART0CXZ51BC1VMQ/the-big-ear-radio-telescope) Ohio State University Radio Observatory · publisher Document1 step from object [The Ohio SETI archive (Big Ear records, 1963–1998)](https://mysteriesdept.com/mysteries/wow-signal/artifacts/ART0CXZ522T14YR/the-ohio-seti-archive-big-ear-records-19631998) Arecibo Wow! project · publisher Document2 steps from object [Arecibo 1420 MHz drift scans, February–May 2020](https://mysteriesdept.com/mysteries/wow-signal/artifacts/ART0CXZ52T8551D/arecibo-1420-mhz-drift-scans-februarymay-2020) Méndez, Ortiz Ceballos and Zuluaga · arXiv-nonexclusive [See all 12 artifacts](https://mysteriesdept.com/mysteries/wow-signal/artifacts) ## See also [ **Phosphine in the clouds of Venus** A 2020 report of phosphine gas in the clouds of Venus, not independently confirmed. ](https://mysteriesdept.com/mysteries/venus-phosphine) [ **Fast radio bursts and the origin of the one-off bursts** Millisecond flashes of radio waves from other galaxies, first reported in 2007. ](https://mysteriesdept.com/mysteries/fast-radio-bursts) [ **Tabby's star (KIC 8462852)** A star in Cygnus that dimmed by up to 20 per cent at irregular times in Kepler data. ](https://mysteriesdept.com/mysteries/tabbys-star) [ **UVB-76, "the Buzzer"** A Russian shortwave station on 4625 kHz sending a repeating buzz since at least 1982. ](https://mysteriesdept.com/mysteries/uvb-76-buzzer) ## References 1. 1.[Méndez, A., Dixon, R., Childers, R. 2026. The Ohio SETI Program: The Last Decades. arXiv (Proceedings of IAU Symposium 404, Advancing the Search for Technosignatures).](https://mysteriesdept.com/sources/SRC0CXZ4CV46NXS/the-ohio-seti-program-the-last-decades)cited 16 times here**SRC** 0CXZ4CV46NXS 1. 2.[Ehman, J. 2010. The Big Ear Wow! Signal (30th Anniversary Report). Big Ear Radio Observatory / NAAPO (bigear.org).](https://mysteriesdept.com/sources/SRC0CXZ4CKA0F1B/the-big-ear-wow-signal-30th-anniversary-report)cited 24 times here**SRC** 0CXZ4CKA0F1B 1. 3.[Gray, R. 1994. A Search of the "Wow" Locale for Intermittent Radio Signals. Icarus.](https://mysteriesdept.com/sources/SRC0CXZ4DJJ72HX/a-search-of-the-wow-locale-for-intermittent-radio-signals)[doi](https://doi.org/10.1006/icar.1994.1199)cited 2 times here**SRC** 0CXZ4DJJ72HX 1. 4.[Gray, R., Marvel, K. 2001. A VLA Search for the Ohio State "Wow". The Astrophysical Journal.](https://mysteriesdept.com/sources/SRC0CXZ4DTC3EQ2/a-vla-search-for-the-ohio-state-wow)[doi](https://doi.org/10.1086/318272)cited 3 times here**SRC** 0CXZ4DTC3EQ2 1. 5.[Gray, R., Ellingsen, S. 2002. A Search for Periodic Emissions at the Wow Locale. The Astrophysical Journal.](https://mysteriesdept.com/sources/SRC0CXZ4E260YRZ/a-search-for-periodic-emissions-at-the-wow-locale)[doi](https://doi.org/10.1086/342646)cited 4 times here**SRC** 0CXZ4E260YRZ 1. 6.[Paris, A., Davies, E. 2015. Hydrogen Clouds from Comets 266/P Christensen and P/2008 Y2 (Gibbs) are Candidates for the Source of the 1977 "WOW" Signal. Journal of the Washington Academy of Sciences.](https://mysteriesdept.com/sources/SRC0CXZ4ESM4Z96/hydrogen-clouds-from-comets-266-p-christensen-and-p-2008-y2)[doi](https://doi.org/10.1063/pt.5.031029)cited 4 times here**SRC** 0CXZ4ESM4Z96 1. 7.[Dixon, R. 2017. Rebuttal of the Comet Hypothesis for the Wow! Signal. North American AstroPhysical Observatory (naapo.org).](https://mysteriesdept.com/sources/SRC0CXZ4F1E4F0K/rebuttal-of-the-comet-hypothesis-for-the-wow-signal)cited 4 times here**SRC** 0CXZ4F1E4F0K 1. 8.[Méndez, A., Ortiz Ceballos, K., Zuluaga, J. 2024. Arecibo Wow! I: An Astrophysical Explanation for the Wow! Signal. arXiv.](https://mysteriesdept.com/sources/SRC0CXZ4D2Y44ST/arecibo-wow-i-an-astrophysical-explanation-for-the-wow)cited 12 times here**SRC** 0CXZ4D2Y44ST 1. 9.[Méndez, A., Ortiz Ceballos, K., Zuluaga, J. et al. 2025. Arecibo Wow! II: Revised Properties of the Wow! Signal from Archival Ohio SETI Data. arXiv.](https://mysteriesdept.com/sources/SRC0CXZ4DAR1PCY/arecibo-wow-ii-revised-properties-of-the-wow-signal-from)cited 7 times here**SRC** 0CXZ4DAR1PCY 1. 10.[Ehman, J. 1998. The Big Ear Wow! Signal: What We Know and Don't Know About It After 20 Years. Big Ear Radio Observatory / NAAPO (bigear.org).](https://mysteriesdept.com/sources/SRC0CXZ4CBG5MP2/the-big-ear-wow-signal-what-we-know-and-dont-know-about-it)cited 2 times here**SRC** 0CXZ4CBG5MP2 1. 11.[Kipping, D., Gray, R. 2022. Could the 'Wow' signal have originated from a stochastic repeating beacon?. Monthly Notices of the Royal Astronomical Society.](https://mysteriesdept.com/sources/SRC0CXZ4EA0349M/could-the-wow-signal-have-originated-from-a-stochastic)[doi](https://doi.org/10.1093/mnras/stac1807)cited 8 times here**SRC** 0CXZ4EA0349M 1. 12.[Caballero, A. 2022. An approximation to determine the source of the WOW! Signal. International Journal of Astrobiology.](https://mysteriesdept.com/sources/SRC0CXZ4EHT082G/an-approximation-to-determine-the-source-of-the-wow-signal)[doi](https://doi.org/10.1017/S1473550422000015)cited 1 time here**SRC** 0CXZ4EHT082G Last edited 27 Oct 2026