Wow! Signal

From TinWiki.org

Wow! Signal circled on print-out

The Wow! Signal is named after a notation made on the side of a computer print out.

Dr. Jerry R. Ehman detected a very strong narrow band radio signal on August 15, 1977 using the Big Ear Radio Telescope. The signal lasted for 72 seconds and gets its name from the fact that Dr. Ehman circled the signal on the computer printout and wrote "Wow!" beside it at the edge of the paper. The signal was in the expected band width that they thought an extraterrestrial civilization would transmit in, and it appeared to have originated outside our solar system.

Though further searches have been done looking at that same area of the sky, the signal has not been detected since.

1 Big Ear Telescope
2 The Signal
3 Also On tinWiki
4 ATS Discussion Threads
5 External Sources

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Big Ear Telescope

Big Ear Radio Telescope

It is noted that this telescope spent more time dedicated to SETI than any other in the world.

The Big Ear was constructed in 1963 at Ohio Wesleyan University and was dismantled in 1998. This particular type of telescope is called the Kraus Type, so named after the designer Dr. John D. Kraus.

The design includes a massive "ground plane" covered in heavy duty aluminum foil. This was a very flat surface that covered an area of 3.2 acres or 500 feet x 280 feet. Larger than 3 American Football fields. At one end of the ground plane stood a flat reflector and the other end a paraboloid reflector. Both reflectors were constructed with a steel frame structure covered in a wire mesh.

Two feed horns were mounted on railroad tracks in 1980 near the flat reflector to receive signals from the parabolic reflector. The feed horns were designed to capture the frequency around 1420 MHz. The tracks allowed the telescope to observe a single point for about an hour by moving along as the Earth rotated. Sadly, at the time the Wow! Signal was detected the feed horns were fixed in position and could only observe a single location for 72 seconds.

The control room and receiving equipment is situated underground and only one other telescope of this design has ever been constructed.

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The Signal

The signal was within what is called the hydrogen line, which is at 1420.406 MHz and was the strongest signal ever received by a radio observatory. It is forbidden for any Earth station to broadcast at this frequency.

The fact that it steadily increased in intensity for 36 seconds and dropped off for the next 36 seconds drew the conclusion that it could not be of terrestrial origin. It followed the exact time and expected intensity fluctuation to only have originated in the area they were observing for those 72 seconds.

At the time of the detection the telescope was pointed to an area in the constellation Sagittarius close to a star named Chi-1 Sagittarii.

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