The Wow! signal

The signal was recorded during a sky survey by the Ohio State Radio Observatory’s Big Ear telescope. The next day, volunteer astronomer Jerry Ehman noticed an unusual sequence in a computer printout and wrote “Wow!” beside it. The telescope’s data encoded signal strength using letters and numbers; the sequence “6EQUJ5” represents measured channel intensities, not a decoded message.

The signal stood out because it was narrowband and much stronger than the surrounding background. It appeared near the frequency associated with neutral hydrogen, a frequency of interest in SETI discussions. Its rise and fall across the telescope’s observation were consistent with a source moving through the instrument’s beam as Earth rotated. These characteristics made it noteworthy, but do not establish that it came from an extraterrestrial transmitter.

Follow-up observations did not detect the signal again. Because it was observed only once, researchers have limited evidence for determining its source. Explanations have included interference and possible natural astrophysical processes, but no proposal has been confirmed. The Wow! signal therefore remains an intriguing, unexplained observation—not proof of extraterrestrial life.