For 72 seconds, a high intensity, narrow-band signal, at a frequency of 1420 MHz, was detected by the telescope. The origin of the signal was near the Chi Sagittarii star group. The signal was so strong, and so unexpected, that Ehrman wrote the single word, "Wow!" next to it -- and it has been thereafter called the "Wow Signal."
Despite many efforts to account for the Wow Signal, there have been no convincing explanations regarding its origins. Ehrman himself, while initially doubtful that it was of extraterrestrial origin -- his first thought was that it was a terrestrial signal that had reflected from the surface of space debris -- has backed off from that position, given that (1) the frequency of the signal, 1420 MHz, is a "protected" frequency, because it is precisely the frequency at which hydrogen (the most common element in the universe) emits, and is reserved for astronomical research; and (2) the "space debris" postulated in Ehrman's initial explanation would have to have "significant and unrealistic constraints on its size and movement" in order to account for the signal.
The Wow Signal, a plot of intensity as a function of time
Repeated attempts to relocate the signal have failed. Whatever it was, it seems to have been a one-time occurrence -- or we haven't had our radio telescopes aimed that way when it's happened again.
Now, however, we're about to try to produce our own version of Wow -- via Twitter. (Source)
The ChasingUFO project is aiming to create a large, focused signal, aimed at Chi Sagittarii -- composed of thousands of Tweets. The National Geographic Channel, as a publicity stunt to celebrate the launch of its new series Chasing UFOs, is sponsoring a mass Twitter event this Friday, June 29, starting at 8 PM Eastern Time and ending at midnight Pacific Time. Any tweets sent during that time with the hashtag #ChasingUFOs will be rolled together and beamed into space, aiming at the spot where Wow was detected.
Me, I'm psyched. I've always been fascinated with Wow -- okay, yeah, maybe there's a conventional explanation for it, but I'm damned if I can see what it might be. Even the frequency is suspicious -- given that 1420 MHz corresponds to one of the main spectral lines of the hydrogen atom, it makes sense that if you were an intelligent alien, you'd have your radio telescope tuned to that frequency -- and also, that if you were sending a signal, you'd choose that frequency because it would be likely to be detected. So my feeling is -- and it is just a feeling -- the Wow signal is the best candidate we currently have for a communiqué from an extraterrestrial intelligence.
So I'm trying to decide what I'm gonna say. I'm thinking that "Hi aliens! We love you! Please don't come here and vaporize us with laser pistols!" might be a little disingenuous. Maybe a simple, "We're curious about you. If you're curious, too, please respond," is more in the spirit of the thing. In any case, I welcome you to join in. Let's give those aliens a great big shout -- and maybe make them sit back on their heels (or tentacles, or whatever), and say, "Wow!"