Hunt for alien life to expand its scope

New, stronger telescopes could examine millions of stars within a generation.

Researching the prospects for life beyond our solar system is moving to the next level. Exoplanet hunters are getting instruments that promise to spot Earth-like planets around alien stars. In some cases, they may even yield crude estimates of how life-friendly such a planet may be.

Meanwhile, the search for extraterrestrial intelligence (SETI) is gaining new capacity to scan the heavens for alien signals. It could produce more analyzed data over the next two years than its researchers have collected over the past half century.

Seth Shostak, who forecast that data bonanza at a meeting at Arizona State University in Tempe earlier this month, readily admits that researchers have monitored only a tiny bit of the cosmos. A senior astronomer at the SETI Institute in Mountain View, Calif., Dr. Shostak explains that "we might have to search millions of star systems" to detect an alien signal. Yet, he says, "The actual number of star systems that radio SETI experiments have carefully examined is fewer than a thousand." [Editor's note: The original version misidentified Arizona State University.]

That's about to change. New systems planned or under construction, such as the SETI Institute's 42-antenna Allen Telescope array, will begin the needed millions-of-stars search. Many of these radio telescopes will be devoted to other radio astronomical missions. But they will be sensitive enough to detect leakage from radio transmissions an alien civilization may be sending domestically.

Avi Loeb and Matias Zaldarriaga at Harvard University have proposed piggy-backing monitoring software on these telescopes to detect alien radio leakage. It will be technically difficult to avoid being fooled by Earth's own leakage. But the Harvard astronomers think it is doable. Shostak forecasts: "SETI experiments will have examined millions of star systems within a generation."

Meanwhile, exoplanet hunters do have something to show for their past efforts. The confirmed planet count is closing in on 300. It's hard to keep an accurate count since new planets are reported frequently. Two more were announced last week. One is Jupiter-size the other is Saturn-size in a star system 5,000 light-years away.

Planets are detected by how their gravitational tug makes their parent star wobble or by catching them when they pass in front of the star. The star system's gravity also can act like a lens focusing distorted images of objects behind them. Planets can be detected by their contribution to this lensing effect.

Most of the planets found are large and orbit close to their stars. Now the hunters' goal is to find the full range of exoplanet types, including Earth-like bodies. Discussing this last month in Nature, Harvard University astronomer Dimitar Sasselov said this goal "will be achieved quickly" with help from missions dedicated to this purpose. France launched such a mission in December. NASA plans to launch one next year.

Dr. Sasselov says, "Exploring planets down to Earth size remains a priority of enormous resonance, both scientific and emotional."

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