The observatory's own answers: the signal was in the beam for 72 seconds and seen in only one of two beams, no variation was detected, no audio was recorded, and the telescope was destroyed by land developers in early 1998.
Institutional memorial site maintained by the North American AstroPhysical Observatory (NAAPO), the volunteer group that ran Big Ear in its last years. No page date.
CLASSIFIEDDeclassifiedFILE NO. 024SHEET 2 OF 4
Testimony
Interviews and witness statements: who, in what role, when and where it was said.
WITNESSJerry R. Ehman, Ph.D., the Big Ear volunteer who found the signal · 2007-07-09
Ehman's full technical account: time, frequency (1420.4556 MHz), the 6EQUJ5 code, the two-horn problem and the follow-up searches. He finds terrestrial origins ruled out or improbable and says an extraterrestrial origin cannot be excluded.
“There is simply too little data to draw many conclusions.” source
Draft completed 9 July 2007, last revised 28 May 2010. Hosted on the Big Ear memorial site run by NAAPO.
CLASSIFIEDDeclassifiedFILE NO. 024SHEET 3 OF 4
Press
Newspaper and magazine coverage, then and now. Linked, never copied.
Newspaper feature on the signal and the man who circled it. Ehman is less convinced than many: he says intelligent senders would have transmitted more than once and suggests an Earth signal reflected off space debris.
“Even if it were intelligent beings sending a signal, they'd do it far more than once.” source
Reprinted on the Big Ear memorial site with the observatory's own bracketed notes.
Collects the objections to the comet paper: Bob Dixon (Ohio State Radio Observatory director in 1977) says the comet was in the wrong position; Alan Fitzsimmons and Seth Shostak know of no comet emitting at 1420 MHz.
“Our telescope was working perfectly normally at the time.” source
Explains the Méndez preprint from the Planetary Habitability Laboratory, University of Puerto Rico at Arecibo: the clouds could be identified, the triggering source could not, and the work is not yet peer-reviewed.
“The only difference between the signals observed in Arecibo and the Wow! Signal is their brightness.” source
CLASSIFIEDDeclassifiedFILE NO. 024SHEET 4 OF 4
Analysis
Our own reading of the file, written from the sources on the other sheets. Opinion is marked as such.
What is beyond dispute: a strong, narrow signal near the hydrogen line was recorded, the printout survives, and the people who ran the telescope describe it in detail. Ehman's own report gives the time, the frequency and the 72-second window, and the observatory's FAQ adds that it was seen in only one of the two beams.
What is missing is a second detection. The signal was looked for again by Big Ear and was not found, and the telescope itself was demolished in 1998. With one event, there is no way to test a repeating source, a moving object or an instrument quirk properly. Ehman summed it up himself: there is simply too little data to draw many conclusions.
Our label is Unexplained. Two natural explanations have been proposed in print. The 2017 comet idea was rejected by the observatory's former director and by comet specialists. The 2024 hydrogen-cloud idea is newer and has some data behind it, but it is a preprint and does not identify the flaring source. It would move to Explained only if an explanation is confirmed by independent work.
What it shows
That on 15 August 1977 Big Ear recorded a narrowband signal near 1420 MHz that stayed in the beam for 72 seconds, according to the man who found it.
That the signal was not seen again by Big Ear, and that the telescope was demolished in 1998.
That two natural explanations have been published, and that the 2017 comet version was rejected by the observatory's own staff and by specialists.
What it doesn't prove
That the signal came from an extraterrestrial intelligence. Ehman says it cannot be ruled out, not that it happened; in 1994 he leaned towards an Earth signal reflected off debris.
That the 2024 hydrogen-cloud explanation is right. It is a preprint, and the authors could not identify the source that would have triggered the flare.
That the signal carried any message. The observatory says no variation was seen in the 72 seconds and no audio recording was made.
The other side
The case for calling it explained: Méndez and colleagues found signals in archived Arecibo data that look like the Wow! signal, only about a hundred times fainter, near the same hydrogen frequency. They attribute them to small, cold hydrogen clouds and argue that a brief, much stronger brightening of such a cloud, triggered by something like a magnetar flare, fits what Big Ear saw. If that holds up, the mystery is a rare natural event, not a missing message.
Reports 200 radio observations of comet 266/P Christensen between November 2016 and February 2017 and concludes that the Wow! signal was likely a natural emission from a Solar System body.
“The investigation discovered that comet 266/P Christensen emitted a radio signal at 1420.25 MHz.” source
Peer-reviewed: Journal of the Washington Academy of Sciences, vol. 103 no. 2 (Summer 2017); arXiv copy linked. Rejected by the Ohio State observatory staff (see astronomynow-2017).
COMMENTARYAbel Méndez, Kevin Ortiz Ceballos, Jorge I. Zuluaga · 2024-08-16
Archived Arecibo data from 2020 show narrowband signals near 1420 MHz resembling the Wow! signal but far weaker. The authors attribute them to cold hydrogen clouds and propose that a sudden brightening of such a cloud, perhaps triggered by a magnetar flare, produced the 1977 signal.
Preprint, not peer-reviewed at the time of writing (revised 11 September 2024).
TO VERIFY Candidates, not yet checked
NAAPO/Ohio State staff rebuttal of the comet paper (6 June 2017) at http://naapo.org/WOWCometRebuttal.html: read over plain http, but the site refuses https, so it cannot be linked under the house rules.
Whether the Méndez et al. 2024 preprint has since been published in The Astrophysical Journal.
The exact number and dates of Big Ear's follow-up observations of the same strip of sky (the Plain Dealer reprint carries an observatory note saying just over 100).
Found, but not linked to a source we trust. Not on the sheets until they are.