The WoW Signals – Strange Incident

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 signal appeared to come from the direction of the constellation Sagittarius and bore the expected hallmarks of extraterrestrial origin.

Astronomer Jerry R. Ehman discovered the anomaly a few days later while reviewing the recorded data. 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.

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. 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.

The Signals

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. 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.

Intensity

The signal intensity was measured as signal-to-noise ratio, with the noise (or baseline) averaged over the previous few minutes. The signal was sampled for 10 seconds and then processed by the computer, which took 2 seconds. 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.

Frequency

John Kraus, the director of the observatory, gave a value of 1420.3556 MHz in a 1994 summary written for Carl Sagan. However, Ehman in 1998 gave a value of 1420.4556±0.005 MHz. This is (50±5 kHz) above the hydrogen line value (with no red- or blue-shift) of 1420.4058 MHz. If due to blue-shift, it would correspond to the source moving about 10 km/s (6.2 mi/s) towards Earth.

Time variation

At the time of the observation, the Big Ear radio telescope was only adjustable for altitude (or height above the horizon), and relied on the rotation of the Earth to scan across the sky. Given the speed of Earth’s rotation and the spatial width of the telescope’s observation window, the Big Ear could observe any given point for just 72 seconds. A continuous extraterrestrial signal, therefore, would be expected to register for exactly 72 seconds,

The Discovery

The Wow! Signal was identified by astronomer Jerry R. Ehman during a SETI (Search for Extraterrestrial Intelligence) project at the Big Ear radio telescope of Ohio State University. The observatory was scanning the sky for any potential signals originating beyond our solar system. What made the Wow! Signal so remarkable was its strength and its brief yet distinctive nature.

The Signature

The signal lasted for a mere 72 seconds but left an indelible mark. Ehman, while reviewing the recorded data, noticed an abrupt and strong 72-second signal in the radio frequency band of 1420 MHz. This frequency is significant in the search for extraterrestrial intelligence because it corresponds to the natural emission of hydrogen, the most abundant element in the universe.

What caught Ehman’s attention was the signal’s intensity, resembling a narrowband signal that one might expect from an artificial source. In the margin of the printout, he circled the sequence and wrote “Wow!” – giving the signal its name.

The Mystery Deepens

Despite multiple attempts to detect a repeat of the Wow! Signal, no subsequent signals of comparable strength or origin have been observed. This lack of repetition has fueled the mystery surrounding its source. The usual suspects, such as satellites or Earth-based interference, were ruled out due to the signal’s unique characteristics and its apparent extraterrestrial origin.

Scientists have speculated on various explanations, including natural celestial phenomena or even a transient signal from a passing satellite, but none of these hypotheses have conclusively explained the Wow! Signal. The lack of concrete evidence or subsequent signals has only intensified the intrigue surrounding this cosmic enigma.

The Search Continues

Decades after the Wow! Signal’s discovery, the quest for extraterrestrial intelligence persists. Advances in technology have allowed for more sophisticated searches, including the use of radio telescopes and other instruments specifically designed to explore the cosmos for signs of intelligent life.

While the Wow! Signal remains unexplained, it serves as a reminder of the vastness of the universe and our continuous efforts to explore the unknown. As technology advances and our understanding of the cosmos deepens, the hope of one day solving the mystery behind the Wow! Signal remains alive, inspiring astronomers and scientists to keep their eyes and ears open to the wonders of the universe.

In the vast silence of space, the Wow! Signal stands as a tantalizing whisper from the cosmic unknown, inviting humanity to continue its pursuit of understanding the mysteries that lie beyond our celestial shores.