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Astronomers announced on Monday that they had taken E.T. off hold and resumed searching for radio signals from extraterrestrial civilizations with a set of radio telescopes in Hat Creek, Calif. The project, part of the Search for Extraterrestrial Intelligence, or SETI, was suspended in April when the University of California's Hat Creek Observatory ran out of money.

Astronomers from the SETI Institute had been using an innovative set of radio telescopes known as the Allen Telescope Array to try to listen in on alien broadcasts from the raft of planets newly found by NASA's Kepler satellite. Under a new deal — as well as a public fund-raising effort that netted $200,000 — the SETI astronomers will share the telescopes with the Air Force, which is interested in using them to track satellites and space junk.

At 6:18 a.m. Pacific Standard Time on Monday, when the stars in Kepler's field of view rose in Hat Creek, the array was back on the job, looking for what Jill Tarter of the SETI Institute here called “technosignatures” of any inhabitants of those planets.

“We know there are planets there,” she said.

SETI's resurrection was announced at the start of a weeklong conference here devoted to results from the Kepler satellite, which is conducting a cosmic Gallup poll to determine the fraction of stars that harbour habitable, Earth-like planets.

About Kepler

An overflow crowd of more than 500 astronomers signed up, and they got their money's worth in the first hour: William Borucki, Kepler's principal investigator, reported that Kepler had confirmed its first “Goldilocks” planet, one that orbits its star in the so-called habitable zone — the right distance from its star to have liquid water on its surface.

Kepler 22b, as it is known, is 2.4 times the size of the Earth and about 600 light years from here. It takes 290 days to orbit its star, which is slightly smaller and dimmer than the Sun. Mr. Borucki said that if it had a reasonable atmosphere, the surface temperature on 22b would be about 72°Fahrenheit, “a very pleasant temperature.”

But whether Kepler 22b is actually habitable depends on its composition and atmosphere, neither of which is known. Kepler finds planets by detecting starblinks when planets pass in front of their own stars; this allows astronomers to measure the sizes of the planets, relative to that of their home stars, but not their masses and thus their densities and compositions.

The size of Kepler 22b, however, puts it in a class of planets known as super Earths, about which little is known since there is no planet in that range in our own solar system. It could be mostly rock, making it about 13 times the mass of the Earth, or it could be mostly gas, like Neptune. Probably, it is somewhere in between, said Mr. Borucki, adding, “We have no planets like this in the solar system.”

He did say that because there could be water there, Kepler 22b was a good target for SETI.

The bounty hardly stops there. Natalie Batalha, Kepler's deputy science team leader and a professor at San Jose State University, unleashed an avalanche of new planet candidates, bringing Kepler's potential bounty to 2,326 exoplanets, or planets outside our solar system. Among them, she said, are 207 objects that are about the size of the Earth and 680 others up to 10 times the size of Earth, or super Earths. In all, 48 of the putative planets are in the Goldilocks zone, Dr. Batalha said.

And so there are plenty of targets for the re-energised Allen Array, named for Paul Allen, the Microsoft co-founder and philanthropist who paid for the array of 42 telescopes. Dr. Tarter said that the SETI effort needed about $100,000 a month to keep operating and that in the long run, the Air Force money would not be enough to keep it alive.

“We are going to need public support,” she said. — New York Times News Service

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