If it sounds too good to be true it probably is, goes the famous adage – and so it goes with extraordinary claims of potential alien signals.

Still, astronomers are puzzling over an incredibly powerful burst of energy that seems to have emanated from the star HD 164595, located some 94 light-years away in the constellation Hercules.

"An international team of researchers has announced the detection of 'a strong signal in the direction of HD164595'," book author Paul Gilster wrote at his blog Centauri Dreams, noting that a Russian radio telescope called RATAN–600 detected the signal last year.

"No one is claiming that this is the work of an extraterrestrial civilisation … But the signal is provocative enough that the RATAN–600 researchers are calling for permanent monitoring of this target," he wrote.

The signal's discoverers are urging the Search for Extraterrestrial Intelligence (SETI) to take a long, hard look at HD 164595.

Seth Shostak, a senior astronomer at the SETI Institute, said that's exactly what the organisation did Sunday night after it heard about the alleged signal, which was supposedly detected on 15 May 2015.

"We looked last night with (the) Allen Telescope Array (ATA) last night and didn't find anything," Shostak, who wasn't involved in the signal's initial detection, told Business Insider. "But like all SETI experiments, you can't prove it's not there, only that it is there by finding the signal again."

An "interesting" signal

Gilster and Shostak are both gleaning their information from a scientific presentation sent to them by Claudio Maccone, an Italian astronomer who collaborated with Russian researchers at RATAN–600.

The deck of slides will allegedly be shown to researchers at the International Astronomical Meeting in Mexico on September 27. (Business Insider contacted Maccone for a copy, but he did not immediately respond; Glister, however, sent us a PDF of the slides.)

128764-bi-signal-1A chart of a powerful (and potentially alien) radio signal that allegedly came from the vicinity of the star HD 164595. Credit: C. Maccone et al./Centauri Dreams

If we're to believe the presentation, the signal from HD 164595 is so intriguing partly because the star is "exactly Sun-like," according to the presentation.

HD 164595 weighs almost exactly the same as the sun (just 1 percent lighter), is 4.5 billion years old (just 100 million years younger), has a similar temperature, and even has a near-identical elemental composition, or 'metallicity'.

Astronomers have also found a Neptune-like planet orbiting the distant star, called HD 164595 b, and Gilster notes there may be other planets there – perhaps smaller, rockier worlds left undetected by telescopes and spacecraft like NASA's Kepler mission.

But the radio signal is what drew Maccone and the Russian researchers he's collaborating with toward the star system in the first place.

Shostak says it's about 2.7 centimetres (1.06 inches) in wavelength and 11 GHz in frequency, which makes it an ultra high-frequency signal that's not too different from a digital TV signal.

Assuming the signal is real, Shostak says it'd have to be incredibly powerful to reach Earth from HD 164595.

"If they're aiming it straight at Earth, it'd require about 50 trillion watts," Shostak said – 50 followed by 12 zeros. "That's a little more than all of humanity uses at any moment, more than all the energy being used by all of our power plants, cars, buses, planes, trains, and so on."

And if the signal is being broadcast in all directions? The power requirement gets even steeper, he said.

"The amount of power you'd need is something like 100 billion billion watts," Shostak says, or a 100 followed by 20 zeroes. That's roughly 100 million times more than a focused, beam-type signal.

"Probably not E.T."

Shostak says no one is holding their breath in hopes that the signal is alien – not even Maccone himself.

For one, says Shostak, the research group took more than a year to say anything about the signal.

128764-bi-signal-2The RATAN-600 radio telescope in Russia. Credit: александр с кавказа/Wikimedia

"It's a gentlemen's agreement that if you find a signal that could be real, you call up someone else to check it out in an effort to convince yourself," he said. "The people who found it didn't think enough to tell other people right away."

The Russian researchers, Maccone told Shostak, didn't do this because "they were shy".

"To me that says they are not so convinced it's ET [extraterrestrial]," Shostak said, noting Maccone even told him that he thinks "it is probably not E.T.".

Second, Shostak says the RATAN–600 radio telescope in Russia (shown above) has a sort of "astigmatism", so it can't verify with great certainty that the signal is coming from a place like the HD 164595 star system.

"If you have an ordinary telescope dish, you can zero on one spot on the sky. That spot is usually fairly small, like aiming a laser pointer," Shostak said. "But their antenna is small in one direction and big in another. It's like a squished egg. When you pick something up, you don't know precisely where it's coming from."

Shostak also said the signal the RATAN–600 facility picked up is wide and "spread all over the dial," which makes it harder to verify.

"It swallows 1,000 MHz of spectrum. It's like they're getting all of the TV stations at once," Shostak said. "You'd know there's a transmission in there, but not exactly where."

Which is why, when SETI looked for the signal, it may not have found it; it could be spread out and weak in every channel, or powerful in one channel but harder to zero in on. "Even if you don't see lights on in the windows, it doesn't mean no one is there," Shostak said. "Maybe you're too far away or not looking at the right time."

He says SETI plans to look for the signal again Monday night using the ATA, but insisted that Maccone and his colleagues need to publish their work – and preferably outside of a Power Point presentation.

"I think that says something itself. We'd all like to know more," he said. "Until that's done, this is 'interesting if true.'"

128764-bi-signal-3A gravitational lens or 'Einstein ring'. The blue ring is a galaxy behind a large galaxy that has distorted spacetime, bending the light around it like a lens. Credit: ESA, NASA/Hubble

So what might it be, if not aliens?

"We have a detection of a single source, much like the famous WOW! signal. The WOW! signal never did repeat, and this one may do the same, in which case we won't know whether it is an actual distant signal or a local event caused by something we haven't figured out," Gilster told Business Insider in an email.

One thing it could be is the accidental work of a gravitational lens: which occurs when a massive object, such as a star, warps the fabric of space enough to collect, focus, and concentrate a signal behind it on a far-off target like Earth.

"I am also interested in the idea that this is a microlensing event caused by the star passing in front of a more distant target," Gilster said, noting astronomers at the Paris Observatory are looking into the possibility.

This article was originally published by Business Insider.

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