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Published on Apr 20, 2007
**********THE WOW! SIGNAL********** The world's most promising and tantalizing candidate signal from an extraterrestrial intelligence to date, the WOW! signal, was gathered by this telescope. Dr. Robert Dixon makes an on-site presentation about "Big Ear."
As the researchers had done thousands of times, they glanced over the radio telescope's computer printouts, not expecting to find anything. But what Dr. Jerry Ehman saw on Aug. 15, 1977 would be recorded all over the world and discussed to this day. On that day's printout was a signal so strong that it catapulted the recorder off the chart. Ehman scribbled "Wow!" on the printout, and this tag is known around the world.
Beginning in 1965, Ohio State University's radio telescope, Big Ear, was used for a premier survey of the radio sky. It found over 20,000 celestial radio sources. Designed by John Kraus, it was about the size of three football fields and consists of a huge metal ground plane with two fence-like reflectors (one fixed and one tiltable). It surveys the sky by remaining stationary. Earth's rotation sweeps its beam (the area of sky it sees) in a narrow circular path through the sky once every day. The beam can be moved slightly up or down by tilting the reflector. The OSU Search for Extra-Terrestrial Intelligence (SETI) program became the longest continuously running electromagnetic search to date. Researchers search in the hydrogen line frequency (1420 mHz), but assume a transmitting civilization would offset their frequency (Doppler shift) to remove their motions with respect to the center of the galaxy, to make a unique reference point.
The 1977 signal seemed to fit all the expected characteristics for communications of intelligent extra-terrestrial origin. It may have been a strong, highly intermittent signal from an alien civilization, which was captured by the telescope as it swept by the earth.
The Wow signal had every characteristic of an extraterrestrial signal. Its narrowband matched the telescope's antenna pattern, which indicated that it was at least at a lunar distance. (The signal from a nearer object would have a wider pattern.) But research showed that it did not come from the moon, a planet, a known star, a galaxy, a publicly known satellite, nor an earth source, which bounced off something in space. Its frequency was near the 1420 mHz hydrogen line, where radio transmissions are prohibited. Amazingly, the signal abruptly turned off as the telescope monitors recorded it. The signal's amazing strength (60 Janskys in a 10 KHz channel) was 30 standard deviations above the mean background noise. Thus, the transmitter used a huge amount on energy. If the source were a rotating lighthouse kind of beacon, the signal might never be found again.