A radio signal first identified as a possible transmission from an extraterrestrial civilization has turned out to be a false alarm, with Russian scientists confirming that it actually came from Earth. Recent reports had suggested that a powerful radio signal from a G-type star 94.4 light years away in the constellation of Hercules might be a deliberate message from an alien species, but it now seems likely that an old Cold War military satellite is the culprit.

According to the SETI Institute, the signal was first received by Russian astronomers in May 2015 using the RATAN-600 radio telescope in Zelenchukskaya at the northern foot of the Caucasus Mountains. However, the news did not filter through to the public until the signal was discussed at a recent presentation where Claudio Maccone, the chair of the International Academy of Astronautics Permanent SETI Committee, was present.

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The signal that seemed to come from the star HD 164595 was very unusual. It had a bandwidth of one GHz, which is a billions of time wider than the bandwidth range that SETI usually uses. Then there was the strength of the signal, which was 0.75 Janskys. A Jansky is equivalent to 10−26 watts per square meter per hertz. For comparison, a mobile phone at about a kilometer away gives off 110 Janskys. To come from 94 light years away, the signal would have needed to be much stronger at its point of origin. If it had been broadcast in every direction, the signal would have consumed 1020 watts or the equivalent of a hundred times all the sunlight reaching the Earth. If the signal was beamed directly at us, it would have needed "only" a trillion watts.

So if this signal did come from someone, then it must be a supercivilization far in advance of our own. Unfortunately, when SETI aimed the Allen Telescope Array (ATA) at HD 164595 on August 28 and 30 to try to locate the signal, the results were negative.

Meanwhile, in an article by TASS, Director of the Institute of Applied Astronomy at the Russian Academy of Sciences Alexander Ipatov stated that the signal was in reality the result of terrestrial interference. Specifically, an old Soviet military either transmitted or reflected the signal picked up by the astronomers. This was later confirmed in a statement by the Special Astrophysical Observatory of the Russian Academy of Sciences, which said, "It can be said with confidence that no sought-for signal has been detected yet."

Source: SETI