Don’t start drawing up your WELCOME TO EARTH posters just yet. Astronomers at the Search for Extraterrestrial Intelligence (SETI) say the “alien signal” splashed across the Internet this week could just as easily have been caused by a passing satellite or even power lines on Earth.

Scientists at the Russian Academy of Science’s Special Astrophysical Observatory first noticed a spike in radio activity on May 15, 2015. The spike appeared in the 2.7 cm wavelength (11 GHz band) and lasted a mere four seconds—a very short transmission indeed, if that’s what it was.

The RATAN-600 radio telescope in Russia. Image credit: александр с кавказа via Wikimedia Commons // CC BY 3.0

The Russian researchers' calculations put the source of the signal in HD 164595, a Sun-like star 28.927 parsecs, or about 94.4 light-years, from here. To date, we’ve found just one planet orbiting the star: the warm, Neptune-like HD 164595 b. Of course, just because we haven’t found others doesn’t mean they’re not there.

For reasons unknown, the Russian astronomers decided to keep news of the “signal” quiet, circulating the information with a select group of other researchers in a presentation and unpublished documents. They also failed to alert the larger ET-search community—a decision that represents a breach in both practice and protocol, according to SETI senior astronomer Seth Shostak, who wrote on SETI's website about the signal.

The news stayed quiet until August 27, when science writer Paul Gilster broke the story on his blog. “Working out the strength of the signal,” he wrote, “the researchers say that if it came from an isotropic beacon, it would be of a power possible only for a Kardashev Type II civilization. If it were a narrow beam signal focused on our Solar System, it would be of a power available to a Kardashev Type I civilization.”

SETI researchers are less willing to speculate. “It’s hard to understand why anyone would want to target our solar system with a strong signal,” Shostak wrote. “This star system is so far away they won’t have yet picked up any TV or radar that would tell them that we’re here.”

The odds are good that the faint “transmission” was actually the product of some form of Earth-based interference, whether from a satellite in near orbit, power lines, or somebody’s microwave. This certainly wouldn’t be the first time kitchen appliances have been caught impersonating extraterrestrials.

"The chance that this is truly a signal from extraterrestrials is not terribly promising, and the discoverers themselves apparently doubt that they’ve found ET," Shostak concluded. "Nonetheless, one should check out all reasonable possibilities, given the importance of the subject."

Part of the problem in SETI research, he told New Scientist, “is that you have a civilisation that is producing signals that can mess you up all the time—and that civilisation is called humanity.”

Regardless of the signal’s source, experts say, it remains an intriguing data point worthy of further study. “It’s not uncommon in astronomy to see a signal we don’t understand,” astronomer Katie Mack told The Register, “but so far, after lots of data gathering, everything has turned out to be some cool new astrophysical process.”

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