PHOTOS: 13 Ways to Hunt Intelligent Aliens
The Hydrogen Line The curious Wow! signal is more or less a perfect match for what would be expected from a received extraterrestrial transmission. It's been closely analyzed as a result, but to date no one has come up with a satisfactory explanation for where the signal came from.
For a start, the signal's intensity was observed to rise and fall over a period of 72 seconds, consistent with the rotation of Earth, and a single source tracking across the sky, through the Big Ear telescope's view. This gave the signal a characteristic signature, caused by objects seen in the sky. It would be nearly impossible for any Earth-bound object to match it.
It also stood out dramatically over the background noise found in deep space, being about 30 times louder than anything else around it. But by far the most interesting thing about this signal was its frequency.
This signal was very sharp, transmitting at only a single frequency. Natural radio sources don't work like that. They spread across a range of frequencies, meaning that the same signal covers a broad band of transmission. The Wow! signal is not like this at all, showing only one very specific frequency at approximately 1420 MHz.