What is the Wow! signal?
The Wow! signal is a strong radio signal from space received on August 15, 1977, by the “Big Ear” radio telescope of Ohio State University in the United States. The telescope was being used for SETI, the search for radio signals from extraterrestrial intelligence.
“Wow!” on the printout
A few days later, the astronomer Jerry R. Ehman, going through the records, found an exceptionally strong signal among the columns of numbers and letters printed out by the computer. Astonished, he circled it in red pen and wrote “Wow!” in the margin, which gave the signal its name. It lasted about 72 seconds, exactly the time it took for the telescope to sweep past one point in the sky.
Why it was thought to be an alien signal
The signal’s frequency was very close to that of the radio waves emitted by hydrogen, the most abundant element in the universe (around 1420 MHz). Because this frequency is a universal landmark, it was thought that “if intelligent beings used radio for communication, they would choose this frequency.” The signal came from the direction of the constellation Sagittarius. But despite many later observations of the same direction, the same signal was never received again.
Theories about its source
Theories include mistaken reception of terrestrial or satellite signals and radio waves from a hydrogen cloud surrounding a comet, but none is conclusive. In 2024 a new theory was published suggesting that a cold hydrogen cloud in space briefly brightened due to radiation from an object with a strong magnetic field, such as a magnetar. Research also continues on other mysterious radio signals from space, such as fast radio bursts. For stories of contact with aliens, see also Open Contact.
