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After 1.5 million days of computer time, SETI@home heads home to probe potential signs of alien civilizations

'We're now approaching the point to do the analysis and write-up,' co-founder tells El Reg

For more than 20 years, SETI@home has sent radio telescope readings to volunteers' home computers to sift for potential signs of extraterrestrial life among the universe's roar of signals. Come the end of this month, that distributed computing effort will cease.

"On March 31, the project will stop sending out new work to users, but this is not the end of public engagement in SETI research," the team said on Monday.

Now it's time to analyze all the blips identified by volunteers' machines – all that potential evidence of alien civilizations.

SETI@home was an early instance of distributed computing. It receives data from the Arecibo radio telescope in Puerto Rico and the Green Bank Telescope in West Virginia. Its software, which runs on participants' computers, attempts to identify signals that deserve closer analysis, and sends back results to scientists to follow up.

There's a lot of data to process. The Arecibo telescope alone produces about 35GB per day for the project, data that gets broken up into 0.25MB work units that get sent over the internet to participating computers. The work units consist of about 107 seconds of 10kHz data slices, centered around the 1420MHz portion of the spectrum.

The project has been overseen since 1999 by the Berkeley SETI Research Center, which manages several related initiatives, such as the Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP) and Astropulse.

'A typical science experiment'

In a phone interview with The Register, computer scientist and software architect David P. Anderson, co-founder of SETI@home, said the project isn't shutting down. "SETI@home is a typical science experiment where you have a hypothesis and collect data and write-up conclusions," he said. "We're now approaching the point to do the analysis and write-up."

Anderson said he is embracing this next phase with a mixture of relief and excitement. "For me personally, this is sort of necessary to finish up this experiment," he said. He added it's unlikely there's an extraterrestrial signal buried in the data, but the information obtained about the likely power threshold for an alien signal will still be valuable.

Since 2002, SETI@home used about 1.5 million days of computer time, Anderson said. In terms of computation, that represents about 2.6e23 floating-point operations (2.6 times 10 to the 23rd power).

Andrew Siemion, director of the Berkeley SETI Research Center and chair for SETI research at the SETI Institute, a separate non-profit, said in an email to The Register that SETI@home helped introduce millions of people around the world to the search for intelligence beyond Earth and the profound questions that arise from such inquiry.

We are looking forward to seeing what candidate signals, if any, the analysis produces

"Many science experiments have a 'data acquisition' phase, a 'data processing' phase and an 'analysis' phase," he said. "SETI@home is now moving into the latter, which is very exciting indeed. We are looking forward to seeing what candidate signals, if any, the analysis produces."

Siemion said the search for intelligent life beyond Earth is in the midst of a dramatic renaissance.

"Whereas the field of SETI was once a very boutique endeavor undertaken by a small cabal of scientists and engineers largely based in the San Francisco Bay Area, today it is rapidly becoming a bonafide part of astronomy, astrophysics and astrobiology, with many research groups around the world engaging the challenge along unique but complementary lines of inquiry," he explained.

One reason for this, Siemion said, arises from the discovery that extrasolar planets – planets that orbit stars – represent the rule rather than the exception. "The average number of planets per star is greater than one, and some 10-20 per cent of stars host a planet of a suitable size and orbital distance liquid water could exist on its surface," he said.

The second reason, he said, is the launch of the Breakthrough Listen Initiative (BLI) in 2015, a 10-year, $100m international project that aims to answer the question, "Are we alone?"

Green space alien with sombrero and drink on a sun lounger

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Siemion is a principal investigator for BLI, which is one of several Breakthrough Initiatives funded by tech billionaires. "A few years ago we were just barely turning our ears toward the cosmos," said Siemion. "Soon every major astronomical observatory in the world will have SETI, or the search for technosignatures, as a part of its scientific program."

As examples of the SETI renaissance, Siemion said BLI has commissioned a new SETI search system based on the MeerKAT array in South Africa and has extended its observational capabilities at the Green Bank Observatory up to 100GHz.

Then there's the Very Large Array (VLA) in New Mexico, which, Siemion observed, is being upgraded with a "commensal" Ethernet interface, meaning its multiple researchers will be able to access its observational capabilities at the same time.

In addition, Siemion pointed to the refurbishment of the Allen Telescope Array and a partnership with the Transiting Exoplanet Survey Satellite (TESS) team to look for anomalies in optical photometry data and provide more detail about newly detected exoplanets.

SETI researchers are also working with the VERITAS telescope and the international Cherenkov telescope community to conduct new surveys for optical pulses, Siemion said. And he expects that next generation telescopes like JWST, the SKA, the ngVLA and the CTA will lead to even better observational capabilities.

"The probability of success in any one of these efforts is difficult to estimate, but whatever the odds were of a successful detection of intelligent life beyond the Earth a few years ago, today they are orders of magnitude higher," he said. ®

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