Wow! signal
The Wow! signal was a strong narrowband radio signal detected by the astrophysicist Jerry R. Ehman on August 15, 1977 by a SETI project at the Big Ear radio telescope of Ohio State University. The signal was apparently of non-terrestrial and non-solar system origin. It lasted for 72 seconds and has not been detected thereafter. All searches so far for the signal were unsuccessful, both by J. R. Ehman and others. The nature of the signal is therefore unknown and only a few possibilities can be ruled out. The bandwidth of the signal is less than 10 kHz. Two different values for its frequency have been given, 1420.356 MHz (J. D. Kraus) and 1420.456 MHz (J. R. Ehman), but both very close to the frequency of 1420.405 MHz produced by the hyperfine transition neutral hydrogen in the universe. Also two possible equatorial coordinates are given: R.A = 19h22m22s ± 5s or 19h25m12s ± 5s, and both dec = -27°03´ ± 20´ (epoch B1950.0). Amazed by the signal, how the narrowband it was, and the exact match to the intensity variation a localized signal would produce in the antenna used, J. R. Ehman circled on the computer printout the "6EQUJ5" letter code (the intensities detected are coded by space = intensity 0, "1"-"9" = intensities 1-9, "A" = intensity 10, "B" = intensity 11, and so on) of the intensity variation and wrote the comment "Wow!" on its side. This comment became the name of the signal. It has been speculated whether interstellar scintillation of a weaker continuous signal — similar to the effect of atmospheric twinkling — could be a possible explanation (although this still would not exclude the possibility for the signal being artificial in its nature). However, even by using the significantly more sensitive Very Large Array, such a signal could not be detected, while the likelihood of a signal below the Very Large Array level could be detected by the Big Ear radio telescope due to interstellar scintillation is extremely low, less than 10-40.
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