The "wow" mystery turns 30

Exactly 30 years ago today, astronomer Jerry Ehman was looking over a printout of radio data from Ohio State University's Big Ear Radio Observatory when he saw a string of code so remarkable that he had to circle it and scribble "Wow!" in the margin. The printout recorded an anomalous signal so strong that it had to come from an extraordinary source.Was it a burst of human-made interference? Or an alien broadcast from the stars? No one knows. The source of the "Wow" signal has never been heard from again - even though astronomers have looked for it dozens of times.Now the SETI Institute is gearing up to look for it one more time, using the latest tool for seeking signals from extraterrestrial civilizations: the Allen Telescope Array in California.The array combines observations from dozens of separate 20-foot-wide (6-meter-wide) radio dishes to produce an instrument that will eventually become more sensitive than the world's largest single-dish telescope, the Arecibo Observatory.

"Once the Allen Telescope Array is up and running, and that should be later this year, there's going to be a small project in which we'll look at the same section where the 'Wow' signal was detected, and of course the same spot on the radio dial," Seth Shostak, senior astronomer at the SETI Institute, told me today. Although that area of the sky has been searched dozens of times before, the Allen Telescope Array will bring more sensitivity and wider spectral coverage to the quest, Shostak said. The renewed search came as welcome news to Ehman, the man behind the "Wow." "Back in 1977, of course, the computers weren't very powerful," he told me. "Nowadays, if you have the money, you can get excellent receivers, filter banks, computers - you can do much more now than you could in 1977." But he cautioned that the search could well come up empty again.