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Wow Signal

Signals from Extraterrestrials is normally considered a paranormal subject by many people but there is serious research in the field is being conducted by main stream science.  The Wow signal was detected by Jerry R. Ehman on August 15, 1977. This was a strong narrowband radio signal. He was working on a SETI project at the Big Ear radio telescope of The Ohio State University which at the time was located at Ohio Wesleyan University’s Perkins Observatory. This signal bore the expected hallmarks of potential non-terrestrial and non-Solar System origin. This signal lasted a full 72 seconds during which the Big Ear observed it but it hasn’t been detected since then. This signal has had media attention.

The Signal

This signal closely matches the expected signature of an interstellar signal. Ehman circled the signal on the computer printout with the comment Wow! He left this comment due to the intensity of the signal found. This signal was the highest detected by the telescope and on the scale it was over 30 times louder than normal deep space. Two different values for its frequency have been given: 1420.356 MHz (J. D. Kraus) and 1420.4556 MHz (J. R. Ehman). The frequency 1420 is significant for SETI searchers because, it is reasoned, hydrogen is the most common element in the universe, and hydrogen resonates at about 1420 MHz. it’s believed that extraterrestrials might use that frequency on which to transmit a strong signal. Seti researchers refer to this area of the spectrum as the waterhole. The frequency of the wow signal matched very closely with the waterhole hydrogen line.


The signal was located in the constellation Sagittarius, near the Chi Sagittarii star group. The original print out of the wow signal, complete with Jerry Ehman’s famous exclamation, is preserved by the Ohio Historical Society. Trying to determine the exact location of the signal was complicated since the Big Ear telescope used two feed horns to search for signals. Each of these feed horns pointed to different directions in the sky following the earth’s rotation. The signal was detected in one of these horns but not the other. The data was processed in a way that makes it impossible to determine which of the two horns that the signal entered. The region of the sky determined to be the area of the signal was in the constellation Sagittarius, roughly 2.5 degrees south of the fifth-magnitude star group Chi Sagittarii. Tau Sagittarii is the closest easily visible star.

Searches for Recurrence of the Signal

The signal was expected to appear three minutes apart in each of the horns, but this did not happen. Ehman looked for months for recurrences of the signal using Big Ear in the months after the detection but didn’t find anything. In 1987 and 1989, Robert Gray searched for the event using the META array at Oak Ridge Observatory, but did not re-detect it.

In July 1995 there was a test of signal detection software by SETI League executive director H. Paul Shuch. He made several drift-scan observations of the ‘Wow’ signal’s coordinates with a 12 meter radio telescope at the National Radio Astronomy Observatory, Green Bank WV, also achieving a null result.

Speculation on the Signal’s Origin

Interstellar scintillation of a weaker continuous signal could be a possible explanation. This doesn’t exclude the possibility of the signal being artificial in its nature. Other speculations include a rotating lighthouse-like source, a signal sweeping in frequency, or a one-time burst. Ehman has stated his doubts that the signal is of intelligent extraterrestrial origin: “We should have seen it again when we looked for it 50 times. Something suggests it was an Earth-sourced signal that simply got reflected off a piece of space debris.

Later he decided that the signal is unlikely to be an Earth-borne signal. This is due to the requirements of a space-borne reflector being bound to certain unrealistic requirements to sufficiently explain the nature of the signal. In his recent writings, Ehman resists “drawing vast conclusions from half-vast data”—acknowledging the possibility that the source may have been military in nature or otherwise may have been a production of Earth-bound humans.

Any other Candidates?

In 1999 the Berkeley University of California launched the SETI@home project to search for extraterrestrial signals. The search is powered by a virtual supercomputer composed of private computers running an application anyone can download and use. Exact numbers of users are difficult to get but Berkeley claims over 3 million users if true this represents a remarkably powerful supercomputer in terms of cost.

SETI@home occasionally finds candidates that normally have easily explained origins such as satellites, quasars, and various equipment glitches but there has been one exception. In March 2003 another candidate was found in the hydrogen waterhole area of the spectrum.

Candidate SHGb02+14a was spotted three times but had some unusual properties. The signal appeared to be coming from a point between the constellations Pisces and Aries. This is problematic because there is no star in this area within 1000 light years. Another odd aspect of the signal was its frequency was drifting. This would happen if the signal was located on a rotating planet but this seems questionable because the drift would indicate a rotation 40 times faster than earths. Finally the signal was very weak and only lasted for about a minute.

There are some problems with the issues against Candidate SHGb02+14a and they are the assumptions. The problem with distance and perceived rotation assumes a planet based signal. What about a spacecraft or satellite. These would explain the weak signal, short duration, and rotation.

The major problem with both the Wow Signal and Candidate SHGb02+14a is their one time occurrence and short duration. Neither allow for the acid test of repeatability or the extraction of intelligence. Both, depending on personal bias, could be taken as evidence of an extraterrestrial intelligence or as evidence of a natural phenomenon we don’t understand yet. There is simply not enough to support either view.

I encourage every one skeptic and believer alike to check out the  SETI@homextraterrestrial Intelligence and presents the opportunity to participate in some amazing science.

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