The first alien civilizations to notice a little water-bearing planet at the right distance from a small yellow star on an outer arm of the Milky Way galaxy might try to contact us.
If they do, scientists now say they know where the signal will originate ? or at least which part of the sky to watch.
The answer is a 3-degree band of sky called the ecliptic, or the plane along which the Earth orbits and eclipses the sun on a regular basis.
“If they exist out there and have known about us for thousands or millions of years and are trying to signal us, it should be easy to detect if we search in the ecliptic,” Johns Hopkins University professor Richard Conn Henry said.
Henry made the proposal during the American Astronomical Society?s annual meeting in St. Louis last week.
Ray Villard of the Space Telescope Science Institute already plans to join the search. In November 2001, the institute publicized Hubble Telescope observations of a planet passing in front of its own star.
“It occurred to me that alien civilizations along the ecliptic would likely be doing similar observations to Earth,” Villard said. “Once they had determined Earth to be habitable, they might initiate sending signals.”
They teamed up with Seth Shostak of the SETI Institute and Steven Kilston of the Henry Foundation, a Silver Spring think tank, to promote the idea.
They propose to use the new Allen Telescope Array (ATA) operated by the SETI Institute and the University of California, Berkeley.
The search will run in the background as the ATA?s radio interferometer network conducts other astronomical observations, according to Berkeley?s Web site.
Already, 42 dishes have begun making observations at the Hat Creek Radio Observatory, 290 miles north of San Francisco, and the array will include 350 antennae at completion.
Like searching for a needle in the haystack, it?s a lot easier if you have a good general idea where you dropped it.
“Knowing where to look tremendously reduces the amount of radio telescope time we will need to conduct the search,” Kilston said.
They can further refine their search by focusing on where the ecliptic intersects the plane of the Milky Way galaxy, home to most of the galaxy?s 100 billion stars.
The two great planes intersect near Taurus and Sagittarius, two constellations opposite each other in the Earth?s sky. That?s where they propose to begin the search.
