1977 Wow! Signal at 35 Years

The Wow! signal was a strong, narrowband radio signal detected by Dr. Jerry R. Ehman on August 15, 1977 while working on a SETI project at the Big Ear radio telescope of Ohio State University. The signal bore expected hallmarks of potential non-terrestrial and non-solar system origin. It lasted for 72 seconds, the full duration Big Ear observed it, but has not been detected again. It has been the focus of attention in the mainstream media when talking about SETI results.

Amazed at how closely the signal matched the expected signature of an interstellar signal in the antenna used, Ehman circled the signal on the computer printout and wrote the comment "Wow!" on its side. This comment became the name of the signal.

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The Wow! signal was a strong narrowband radio signal detected by Jerry R. Ehman on August 15, 1977, while working on a SETI project at the Big Ear radio telescope of The Ohio State University then located at Ohio Wesleyan University's Perkins Observatory, Delaware, Ohio.^[1] The signal bore expected hallmarks of potential non-terrestrial and non-Solar System origin. It lasted for the full 72-second duration that Big Ear observed it, but has not been detected again. The signal has been the subject of significant media attention.

Amazed at how closely the signal matched the expected signature of an interstellar signal in the antenna used, Ehman circled the signal on the computer printout and wrote the comment "Wow!" on its side. This comment became the intensity variation of the signal. A space denotes an intensity between 0 and 1, the numbers 1 to 9 denote the correspondingly numbered intensities (from 1.000 to 10.000), and intensities of 10.0 and above are denoted by a letter ('A' corresponds to intensities between 10.0 and 11.0, 'B' to 11.0 to 12.0, etc.). The value 'U' (an intensity between 30.0 and 31.0) was the highest detected by the radio telescope, on a linear scale it was over 30 times louder than normal deep space.^[1] The intensity in this case is the unitless signal-to-noise ratio, where noise was averaged for that band over the previous few minutes.^[2]

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 MHz 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, thus extraterrestrials might use that frequency on which to transmit a strong signal.^[1] The frequency of the Wow! signal matches very closely with the hydrogen line, which is at 1420.40575177 MHz. The two different values given for the frequency of the Wow! signal (1420.356 MHz and 1420.4556 MHz) are the same distance apart to the hydrogen line—the first being about 0.0498 MHz less than the hydrogen line, and the second being about 0.0498 MHz more than the hydrogen line. The bandwidth of the signal is less than 10 kHz (each column on the printout corresponds to a 10 kHz-wide channel; the signal is only present in one column).

Wow! signal