January 11, 2007
Do extraterrestrials sweep their skies with radar to scan for
incoming missiles?
If so, Avi Loeb of the Harvard-Smithsonian Center for Astrophysics in
Cambridge, Massachusetts, thinks he can find the radio signals leaked
from warring alien civilizations...
He might also be able to catch their version of reality TV and talk radio.
The concept is different than other radio programs in the search for
extraterrestrial intelligence (SETI) that look for high-frequency
signals deliberately beamed across space to make contact with distant
civilizations.
Extraterrestrials may not emit such beacons, Loeb theorizes.
"However, our own civilization is transmitting power
unintentionally through radio and TV broadcasting and military radars,"
he said in a videotaped presentation played Wednesday to reporters at a
meeting of the American Astronomical Society in Seattle, Washington.
"An interesting question is whether we can eavesdrop on another
civilization at the frequencies that we are ourselves transmitting in,"
he said.
(See related story: "Are Neighborhood Aliens Listening to Earth Radio?" [September 7, 2006].)
Piggyback Search
Loeb believes he can detect the leaked signals by piggybacking
his search on a new generation of radio telescopes designed to study
low-frequency radio emissions in the distant, infant universe.
He and his colleagues hope to test the theory with the Mileura
Wild-Field Array currently under construction in Australia and is
slated to start operations in 2008.
In its current configuration, the array will be sensitive to any
Earth-like civilizations that may exist on a planet orbiting one of
about a thousand stars up to 30 light-years away, Loeb said.
Future observatories, such as the Square Kilometer Array proposed for
development in Australia or southern Africa, could detect Earth-like
planets ten times farther away, which would encompass 100 million
stars.
If radio emissions were detected from a distant planet,
additional observations could tell astronomers about the host star's
mass, the orbit of the planet, and the distance between the two, Loeb
noted.
"That by itself would allow us to decide whether there could be liquid
water on the surface of the planet and whether that can support life as
we know it," he said.
(See a gallery of what life on other planets might look like.)
High Frequency
Peter Backus is the observing programs manager at the SETI
Institute in Mountain View, California. He said the institute's radio
telescope under construction in northern California is also exploring
new regions of the frequency spectrum.
"Just as [Loeb]'s paper talks about the low-frequency end,
we're expanding up to higher frequencies that really haven't been
searched at all," he said at the briefing.
Previous searches looked at the frequency range between 1,200 and 3,000 megahertz.
The new telescope, named the Allen Telescope Array after its
primary donor, Microsoft cofounder Paul Allen, will go up to 11,200
megahertz, Backus said.
Preliminary tests reveal that nearly 90 percent of that band is available to detect extraterrestrial transmissions.
The array configuration will also allow simultaneous examinations of several patches of the sky.
"That gives us a lot of flexibility in what we can do and how much we can do at one time," Backus said.
Ultimately the array will consist of 350 20-foot (6-meter) dishes
spread out over 2,300 feet (700 meters). Currently 36 of the antennas
are online with 42 expected to boot up this summer.
Though originally conceived as a telescope primarily for SETI,
Backus said radio astronomy projects will direct where the array
points. Within the field of view are bound to be several of the million
or so SETI candidate stars.
"Although a certain fraction of the time we'll have to point the array to follow up on result candidates," he noted.
http://news.nationalgeographic.com/news/
2007/01/070111-alien-life.html
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