* Astronomy

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RE: Optical SETI

Blobrana · L

For several decades, astronomers have been aiming sensitive radio receivers toward the heavens hoping to eavesdrop on signals generated by beings on planets elsewhere in the galaxy. Nothing yet, of course, but now an international team of researchers is proposing to look for flashes from alien laser beams as well using gamma-ray telescopes.
Gamma-ray telescopes are designed to detect the highest-energy particles of light: photons from exploding stars and the like. But if their ultra-fast, ultra-sensitive cameras are tuned to the proper wavelength, they also can detect faint flashes of optical light of the sort that might come from lasers positioned thousands of light-years away.

"There are 20 to 30 naturally occurring light flashes recorded every second" by gamma-ray telescopes around the world, says astrophysicist Joachim Rose of the University of Leeds in the U.K. The telescope software usually ignores the flashes because it is configured to reject "anything that it doesn't expect," he says.

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An optical telescope at the Oak Ridge Observatory, 35 miles west of Boston, is the first to be used exclusively for the Search for Extraterrestrial Intelligence project.
Scientists began using optical telescopes on the SETI project in 1998 at Oak Ridge and other sites. Until now, they've had to share time on optical telescopes with other astronomers doing different work. The new 72-inch telescope will be used exclusively for SETI.

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After 20 years of listening for signs of life elsewhere in the universe, The Planetary Society is now ready to watch the skies. On April 11, 2006 the Society will dedicate a brand new optical telescope at an observatory in Harvard, Massachusetts, designed solely to search for light signals from alien civilizations -- a search known as Optical SETI (OSETI).

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Title: Optical SETI with Imaging Cherenkov Telescopes
Authors: J. Holder, P. Ashworth, S. LeBohec, H.J. Rose, T.C. Weekes

The idea of searching for optical signals from extraterrestrial civilizations has become increasingly popular over the last five years, with dedicated projects at a number of observatories. The method relies on the detection of a brief (few ns), intense light pulse with fast photon detectors.
Ground-based gamma-ray telescopes such as the Whipple 10m, providing a large mirror area and equipped with an array of photomultiplier tubes (PMTs), are ideal instruments for this kind of observation if the background of cosmic-ray events can be rejected.

Researchers report here on a method for searching for optical SETI pulses, using background discrimination techniques based on the image shape.

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