Eavesdropping on ET Sooner Than We Think
SEATTLE -- On Wednesday, January 10, here at the American Astronomical Society Meeting, theorist Dr. Avi Loeb from Harvard Smithsonian Center for Astrophysics led a press conference on the search for ET. "Soon, we may be eavesdropping on signals from Galactic civilizations," said Loeb. "This is the first time in history that humans will be capable of finding a civilization like ours among the stars." Loeb asserts that the proposed search will find "leakage" from transmissions equivalent to our broadcast television or military radars. SETI Institute's Project Phoenix and UC Berkeley's SERENDIP have both had the technical capability to detect intentional signals--beamed at Earth--with the equivalent power to military radars. Loeb's search would expand the frequency range over which searches are conducted.
Loeb and his co-author Matias Zaldarriaga (CfA) suggest looking for accidental leakage from an alien civilization. They point out that the new Mileura Wide-Field Array's Low Frequency Demonstrator (MWA-LFD), which is designed to study frequencies of 80-300 Megahertz, will pick up the same frequencies used by Earth technologies. On Earth, military radars are the most powerful broadcast sources, followed by television and FM radio. If similar broadcast sources exist on other planets, facilities like MWA-LFD might detect them. A SETI program at the MWA-LFD would complement other SETI projects. It will observe a larger area of the sky over a longer period of time and in a different frequency range.
"The MWA-LFD is a science instrument intended to study the distant, young universe," explained Zaldarriaga. "But by piggybacking onto its normal observations, SETI researchers could use it to look for E.T. civilizations." Loeb and Zaldarriaga calculate that by staring at the sky for a month, the MWA-LFD could detect Earth-like radio signals from a distance of up to 30 light-years, which would encompass approximately 1,000 stars. More powerful broadcasts could be detected to even greater distances. Future observatories like the Square Kilometer Array could detect Earth-like broadcasts from 10 times farther away, which would encompass 100 million stars.
Dr. Peter Backus, Research Scientist at SETI Institute also spoke at the press conference. He stated that the MDA-LFD represents a good example of the power of the new generation of radio telescopes. Taking advantage of advances in technology, these telescopes are more powerful and flexible than the traditional, large radio telescopes. Using this same design model, "large N, small D" (a large number of small diameter dishes) the Allen Telescope Array (ATA) will ultimately have 350 dishes, each only 6 meters across. The combination of these dishes will have the equivalent sensitivity of the Very Large Array in New Mexico and the Green Bank Telescope in West Virginia. Using programmable electronics, the signals from the 350 dishes can be combined to form up to 16 virtual antennas, each making independent observations. At the same time, other electronics can image an area of the sky at two different frequencies. The ATA will expand the search to higher frequencies that have far less interference and background noise than the lower frequencies that will be observed by the MWA-LFD.
Backus feels that this proposed low-frequency search is a good first step in exploring the lower frequencies for leakage or non-intentional signals. The unknown properties of such extraterrestrial transmissions will continue to provide challenges for low frequency searches. He looks forward to the outcome of this new observing project with the MWA-LFD.
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