What did the wow signal from deep space mean?

On August 15, 1977, one of the most mysterious events in the history of space exploration happened. Dr. Jerry Ehman, while working on the Big Ear radio telescope as part of the SETI project, recorded a strong narrow-band space radio signal. Its characteristics (transmission bandwidth, signal-to-noise ratio) were as expected from a signal of extraterrestrial origin. Amazed by this, Ehman circled the corresponding characters on the printout and signed "Wow!" in the margin. This signature gave the signal its name.

The signal came from a region of the sky in the Sagittarius constellation, about 2.5 degrees south of the Hee star group. However, after years of waiting for something like this to happen again, nothing happened.

Scientists state that if the signal was of extraterrestrial origin, then the beings who sent it must belong to a very, very advanced civilization. To send such a powerful signal, you need at least a 2.2 gigawatt transmitter, which is much more powerful than any one on earth (for example, the HAARP system in Alaska, one of the most powerful in the world, is supposedly capable of transmitting a signal up to 3600 kW).

As one of the hypotheses explaining the strength of the signal, it is assumed that the initially weak signal was significantly amplified due to the action of the gravitational lens; however, this still does not exclude the possibility of its artificial origin. Other researchers suggest the possibility of rotation of the radiation source like a beacon, a periodic change in the frequency of the signal or its single occurrence. There is also a version that the signal was sent from a moving alien starship.

In 2012, on the 35th anniversary of the signal, the Arecibo Observatory sent a response of 10,000 coded tweets towards the alleged source. However, it is unknown whether anyone received them. Until now, the wow signal remains one of the main mysteries for astrophysicists.