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The Wow Signal

Page history last edited by PBworks 13 years, 9 months ago



"... the strangest signal I had ever seen ... At first, I thought it was an earth signal reflected from space debris, but after I studied it further, I found that couldn't be the case."

-- Jerry Ehman, Ohio State astronomer"



The Wow! signal was a strong narrowband radio signal detected by professor 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 earmarks of potential non-terrestrial and non-solar system origin. It lasted for 72 seconds 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 nearly 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.


Statistical Data

Bandwidth: <10 kHz

Frequency: 1420.356 MHz (J. D. Kraus) or 1420.456 MHz (J. R. Ehman)


Reference Signal: 1420.405 MHz (Hydrogen Line)


Possible Sources?

Sources ruled out:

  • The requirements of the space-borne reflector hypothesis have been found to be bound to certain unrealistic requirements -- rendering it insufficient to explain the nature of the signal.
  • Frequencies near the hydrogen line (1420MHz) are "protected spectrum". Transmission in around that frequency are prohibited both on and off Earth by international agreement -- for astronomical purposes.



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


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.


"Either the Wow! signal was the intercepted radiation from another civilization, or it's a previously undiscovered astrophysical phenomenon. Either possibility is mind-boggling."

-- Paul Shuch, the SETI League


Reference Links

Unsorted Information


A source at this distance using a transmitting dish as big as the Arecibo radio telescope (the largest in the world) would require a 2.2 gigawatt transmitter-extraordinarily powerful but not out of the question. Another possibility is that a much weaker signal from a more remote source may have experienced gravitational microlensing by an intervening star. More than 100 subsequent searches of the same region of sky have failed to recover the signal.


an intriguing feature of the Wow signal: the manner in which it rose and fell over the course of 72 seconds. The Ohio State survey kept the telescope fixed, letting the Earth's daily spin rotate the heavens through its narrow beam. The "beam," of course, was the elongated patch of sky to which the telescope was sensitive - the direction from which it could pick up cosmic signals. The sensitivity was greatest at the center of the beam, falling off to either side. Given the size of the Ohio State beam, this rise and fall should take 72 seconds. And for the Wow signal, it did. Now contrast this with what you'd expect if the telescope had merely been briefly flooded by an interfering terrestrial signal. The intensity would suddenly switch full on, and then, sometime later, switch off. Even if the interference was due to a low-Earth orbit satellite, a source that might cause a rise and fall in intensity, you wouldn't expect it to fortuitously last for 72 seconds.



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