Could aliens be flashing us? Astronomers in the US think they might be.
With funding from a Silicon Valley-based Russian tech billionaire, they've set up an array of telescopes that will be looking out for nanosecond-long bursts of light they believe could be a form of interstellar communication.
"When it comes to intelligent life beyond Earth, we don't know where it exists or how it communicates," said Yuri Milner, the founder and financial backer of Breakthrough Initiatives, a programme aimed at locating extraterrestrial life.
"Our philosophy is to look in as many places, and in as many ways, as we can."
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The latest effort involves sweeping the sky with four 12m telescopes at the Fred Lawrence Whipple Observatory in Arizona known as VERITAS, which stands for Very Energetic Radiation Imaging Telescope Array System. It's normally used for detecting gamma rays, but has been repurposed to look for near-instantaneous bursts of light, which could carry information.
"Optical communication has already been used by NASA to transmit high-definition images to Earth from the Moon, so there's reason to believe that an advanced civilization might use a scaled-up version of this technology for interstellar communication," said Andrew Siemion, of the University of California Berkeley's SETI Research Center.
"Using the huge mirror area of the four VERITAS telescopes will allow us to search for these extremely faint optical flashes in the night sky, which could correspond to signals from an extraterrestrial civilisation," added Jamie Holder, physicist at the University of Delaware.
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VERITAS was previously used to study Boyajian's Star, which made headlines in 2017 when measurements suggested it might be surrounded by an alien megastructure known as a Dyson sphere. Follow-up measurements found it was likely just dust.
Breakthrough Initiatives said in a release most of the stars it'll be targeting in its new search are located 10 to 100 times closer than Boyajian's Star, so will be able to pick up signals up to 10,000 times fainter.