An anonymous reader cites a report on The Guardian: A former analyst with the US Department of Defence is on the trail of a 'cold case' -- an unexplained signal that some believe could have come from extraterrestrials. Way back in 1977 something amazing happened. Astronomer Jerry Ehman was using the Ohio State University's Big Ear radio telescope to sweep the sky for possible signals from extraterrestrial civilisations. He found something. While pointing towards a grouping of stars called Chi Sagittarii on 15 August, he received a powerful blast of radio waves that lasted for 72 seconds. He circled it on the readout and wrote: "Wow!" Analysis of the signal showed that it displayed all the hallmarks of coming from interstellar space, and it became something of a cause celebre for those involved in SETI, the search for extraterrestrial intelligence. The trouble is that despite numerous attempts, the signal has never been observed again and so remains unexplained. Until now perhaps, thanks to the work of Professor Antonio Paris of St Petersburg College, Florida. Known as 266P/Christensen and 335P/Gibbs, they have never been investigated before because they were only discovered in 2006 and 2008 respectively. Paris found that they were both in the vicinity of Chi Sagittarii on the day that the 'Wow!' signal was detected. This could be significant because comets are surrounded by clouds of hydrogen gas that are millions of kilometres in diameter. Comet 266P/Christensen will pass the Chi Sagittarii star group again on 25 January 2017, while 335P/Gibbs will make its passage on 7 January 2018. Paris plans to observe these events to look for a recurrence of the mystery signal.In some other news, cosmologist and theoretical physicist, Stephen Hawking says he doesn't expect the humanity to find intelligent alien life for at least another 20 years.