June 6, 2008 -- Scientists scouring the skies for radio waves from any extraterrestrial neighbors had an epiphany recently: Assume ET knows about us and wants to make contact.
Under that framework, the best place to look for cosmic neighbors would be around stars that lie more or less along lines of sight of Earth, a region known as the ecliptic, or the plane of Earth's orbit.
From this vantage point, an extraterrestrial civilization would be able to detect Earth as it passes in front of the sun, much the same way scientists on Earth have found planets circling stars beyond our solar system.
The ecliptic encompasses about 3 percent of the sky.
"Our team hopes this is a concept that should lead rapidly to the detection of other civilizations -- if they exist," Johns Hopkins University astronomer Richard Henry told reporters at the American Astronomical Society meeting this week in St. Louis, Mo.
"It's conceptual breakthrough," Henry said. "If the hypothesis is correct, they know Earth exists, and they know there is life on Earth."
Advanced civilizations would have the tools to make a chemical analysis of Earth's atmosphere, Henry said, which would reveal our planet's atmosphere is rich with water and oxygen.
"The inescapable implication is that Earth has life," he said.
Advocates of the Search for Extraterrestrial Intelligence, or SETI, believe that advanced civilizations would spend the resources necessary to make contact with their cosmic neighbors, particularly those within relatively direct earshot.
"Knowing where to look tremendously reduces the amount of radio telescope time we will need to conduct the search," Henry said.
The California-base SETI Institute is building a dedicated array of telescopes to hunt for alien radio signals. Henry and his team want to use the observatory to comb stars in the plane of Earth's orbit.
The first 42 radio dishes of the Allen Telescope Array were activated in October. Upon completion, the array, which is located in Hat Creek, Calif., just north of Lassen Volcanic National Park, will have 350 dishes.
Microsoft co-founder Paul Allen provided the seed money for the project, which is built around commercially available, 20-foot diameter radio dishes and telecommunications equipment.
Combined, the network has a wide field of view that is ideal for rapid surveys of the sky. Partners in the project include the University of California at Berkeley, the National Science Foundation and several corporate and individual donors.