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Technical details The circled letter code 6EQUJ5 describes the intensity variation of the signal. A space denotes an intensity between 0 and 0.999.., the numbers 1-9 denote the correspondingly numbered intensities (from x.0 to x.999...), and intensities of 10.0 and above are denoted by a letter ('A' corresponds to intensities between 10.0 and 10.999..., 'B' to 11.0 to 11.999..., etc). The value 'U' (an intensity between 30.0 and 30.999...) was the highest ever detected by the telescope.• 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). 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 the hydrogen line at 1420.405 MHz. Two possible equatorial coordinates are given: Both coordinates give dec. = -27°03´ ± 20´ (epoch B1950.0).• As the Big Ear telescope was fixed, and used the rotation of the Earth to look at different parts of the sky, the presence of the highest intensity in the centre of the detection is what would be expected for an extraterrestrial source. The length of the signal, 72 seconds, also corresponds to an extraterrestrial origin. A local source would have a shifted peak, and it would be a large coincidence for it to last for exactly 72 seconds.• Searches for recurrence of the signal The Big Ear telescope used two beams to search for signals; the Wow signal was detected in the first of these beams. It should also have appeared in the second beam a mere 3 minutes later; it didn't.• Ehman unsuccessfully looked for recurrences of the signal using Big Ear in the month after the detection.• In 1987 and 1989, Robert Gray searched for the event using the META array at Oak Ridge Observatory, but did not re-detect it.• Gray also searched for the signal using the Very Large Array, which is significantly more powerful than Big Ear in 1995 and 1996.• Gray also searched for recurrences of the event in 1999 using the University of Tasmania's Hobart 26m radio telescope.• Six 14-hour observations were made at positions in the vicinity, but did not detect anything similar to the Wow signal.• Speculations on the origin It has been speculated that interstellar scintillation of a weaker continuous signal — similar, in effect, to atmospheric twinkling—could be a possible explanation, although this still would not exclude the possibility of 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, and the probability that a signal below the Very Large Array level could be detected by the Big Ear radio telescope due to interstellar scintillation is low.• Other speculations include a rotating lighthouse-like source or a signal sweeping in frequency. 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-bound signal that simply got reflected off a piece of space debris."• He later recanted his skepticism somewhat after further research scientifically relegated an Earth-bound signal to be astronomically unlikely, due to the requirements of a space-borne reflector being bound to certain unrealistic requirements to sufficiently explain the nature of the signal. Also, the 1420 MHz signal is problematic in itself in that it is "protected spectrum" or bandwidth in which terrestrial transmitters are forbidden to transmit in. In his most recent writings, Ehman resists "drawing vast conclusions from half-vast data," but after applying Occam's Razor, states than an intelligent extraterrestrial origin for the Wow! signal is the only explanation posited thus far that cannot be ruled out. The signal is referenced in the popular TV series "The X-Files" in the second season opening episode "Little Green Men". In that episode, Agent Scully investigates the provenance of an unknown radio signal that has sent her partner Agent Mulder off to the SETI installation at Arecibo in Puerto Rico. Location in the night sky Tau Sagittarii is slightly cooler than the sun, light orange giant star in the constellation Sagittarius, 120 light years from earth. It is also the closest visible star in the night sky to the origin of the 1977 wow signal. The location of the signal was, at (epoch J2000.0) Right Ascension (On the positive horn): 19h25m31s +/- 10s Right Ascension (On the negative horn): 19h28m22s +/- 10s Declination (Is the same for both horns): -26d57m +/- 20m | ||||||||||
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