John Kraus, the director of the observatory, gave a value of 1420.3556 MHz in a 1994 summary written for Carl Sagan. The Wow! signal's highest measured value was "U" (an intensity between 30 and 31), that is thirty standard deviations above background noise. The numbers 1 to 9 denoted the correspondingly numbered intensities (from 1 to 9) intensities of 10 and above were indicated by a letter: "A" corresponded to intensities between 10 and 11, "B" to 11 to 12, and so on. In this particular intensity scale, a space character denoted an intensity between 0 and 1, that is between baseline and one standard deviation above it.
The result for each frequency channel was output on the printout as a single alphanumeric character, representing the 10-second average intensity, minus the baseline, expressed as a dimensionless multiple of the signal's standard deviation. The signal was sampled for 10 seconds and then processed by the computer, which took 2 seconds. The signal intensity was measured as signal-to-noise ratio, with the noise (or baseline) averaged over the previous few minutes. The signal itself appeared to be an unmodulated continuous wave, although any modulation with a period of less than 10 seconds or longer than 72 seconds would not have been detectable. The string 6EQUJ5, commonly misinterpreted as a message encoded in the radio signal, represents in fact the signal's intensity variation over time, expressed in the particular measuring system adopted for the experiment. Signal measurement Plot of signal intensity versus time fitted with a Gaussian function. The event was later documented in technical detail by the observatory's director.
SETI WOW SERIES
While perusing data collected on August 15 at 22:16 EDT (02:16 UTC), he spotted a series of values of signal intensity and frequency that left him and his colleagues astonished. īy 1977, Ehman was working at the SETI project as a volunteer his job involved analyzing by hand large amounts of data processed by an IBM 1130 computer and recorded on line printer paper.
The radio telescope was located near the Perkins Observatory on the campus of Ohio Wesleyan University in Delaware, Ohio. In 1973, after completing an extensive survey of extragalactic radio sources, Ohio State University assigned the now-defunct Ohio State University Radio Observatory (nicknamed "Big Ear") to the scientific search for extraterrestrial intelligence (SETI), in the longest-running program of this kind in history. In a 1959 paper, Cornell University physicists Philip Morrison and Giuseppe Cocconi had speculated that any extraterrestrial civilization attempting to communicate via radio signals might do so using a frequency of 1420 megahertz ( 21-centimeter spectral line), which is naturally emitted by hydrogen, the most common element in the universe and therefore likely familiar to all technologically advanced civilizations.
Many hypotheses have been advanced on the origin of the emission, including natural and human-made sources, but none of them adequately explain the signal.Īlthough the Wow! signal had no detectable modulation-a technique used to transmit information over radio waves-it remains the strongest candidate for an extraterrestrial radio transmission ever detected.
SETI WOW FULL
The entire signal sequence lasted for the full 72-second window during which Big Ear was able to observe it, but has not been detected since, despite several subsequent attempts by Ehman and others. He was so impressed by the result that he circled on the computer printout the reading of the signal's intensity, "6EQUJ5", and wrote the comment "Wow!" beside it, leading to the event's widely used name. Ehman discovered the anomaly a few days later while reviewing the recorded data. The signal appeared to come from the direction of the constellation Sagittarius and bore the expected hallmarks of extraterrestrial origin.Īstronomer Jerry R. The Wow! signal was a strong narrowband radio signal detected on August 15, 1977, by Ohio State University's Big Ear radio telescope in the United States, then used to support the search for extraterrestrial intelligence. The original printout with Ehman's handwritten exclamation is preserved by Ohio History Connection.
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