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Radio eyes open wide

SETI Institute
Dishes spread out across a California valley as part of the Allen Telescope Array.


Searchers for alien signals have just christened a new set of 42 radio eyes - a computer-coordinated array of antennas that is destined to spread even wider across a California valley in the years to come.

The astronomers behind the project plan to use the $50 million Allen Telescope Array to bring the search for extraterrestrial intelligence to a whole new level. But the first picture produced by the array, showing atomic hydrogen in the Andromeda Galaxy, demonstrates that they can do much, much more than just looking for E.T.

Thursday's dedication drew a flock of notables to the arid, scruffy telescope site - near the town of Hat Creek, 300 miles northeast of San Francisco. Perhaps the most notable notable was software billionaire Paul Allen, who provided the telescope with millions of dollars in seed money, as well as its name.

"I'm just very happy to see it all working," the Redding Record Searchlight quoted him as saying.

In a news release issued by the University of California at Berkeley - which has partnered with the SETI Institute to operate the telescope - Allen hailed the project as "a potential breakthrough" in the use of large arrays of relatively small antennas for radio astronomy.

Unlike large single dishes, such as the 1,000-foot-wide Arecibo Observatory in Puerto Rico, the Allen Telescope Array knits together a virtual web of data from platoons of 20-foot-wide dishes. The signal processing system produces the same quality of data you'd get from a 130-foot-wide dish, SETI Institute senior astronomer Seth Shostak said in a Space.com commentary.

"That wouldn't knock the hosiery off most radio astronomers, but it does start to become a serious instrument," Shostak told me today from Redding.

The sock-knocking would happen a few years from now, if and when the telescope system grows to its anticipated full complement of 350 antennas (at an estimated additional cost of $41 million). That would make the array the equivalent of a 300-foot-wide antenna like the Green Bank Telescope in West Virginia, at the birthplace of SETI astronomy.

"It would be one of the most powerful instruments in the world, actually," Shostak said.

Over the next quarter-century, the SETI Institute figures that the Allen Telescope Array could collect 1,000 times more data than has been gathered in the 47-year history of search for extraterrestrial intelligence - in part because the array would be used for the SETI quest 24 hours a day, seven days a week.

Millions of stars could be checked for telltale signals, as opposed to the 1,000 or so checked so far. If you accept SETI pioneer Frank Drake's estimate that our galaxy of 100 billion stars might have 10,000 alien civilizations, you'd have to check millions of stars to give yourself a fair chance of detecting E.T.'s signal. "That's why I think the next couple of dozen years could be very interesting," Shostak said.

But the design of the telescope array allows for multitasking: Other radio-astronomy projects could be taken on simultaneously with the search for alien signals. Among those potential projects are the usual cosmic mysteries: pulsars, black holes, starburst galaxies, gamma-ray bursts, dark matter and gravitational-wave studies.

SETI Institute / UC-Berkeley
A radio image of the Andromeda Galaxy, mapping
atomic hydrogen, looks like a false-color doughnut.


One of the first projects will be to map the distribution of neutral atomic hydrogen over a wide swath of the sky - an endeavor that could shed light on the process of galaxy evolution and set the stage for future studies of dark energy.

The array's first images illustrate what radio astronomy can bring to bear: The Allen Telescope Array's first radio image makes the Andromeda Galaxy look like a false-color doughnut. The hole in the middle indicates that the galaxy's central star factory is getting close to shutting down.

In contrast, an image of the Pinwheel Galaxy looks more like a solid disk. That means that hydrogen is more evenly distributed throughout the galaxy - and that star formation is still going strong.

Once the Allen Telescope Array reaches its full potential, it will be a speed demon for collecting such astronomical data, thanks to its wide-angle view of the sky, Shostak said. "If there's one adjective that describes this telescope and sets it apart from other telescopes, it's speed," Shostak said.

To see more of the array, check out the SETI Institute's ATA Cam and image gallery. And to hear more about the array - as well as other facets of the SETI biz - you must click on this pilot podcast that Shostak and I cooked up a year ago.