Spaceflight Insider

Strange signal detected by Russian radio telescope

ratan-600 radio telescope detects signal

The RATAN-600 radio telescope in Russia. On May 15, 2015, it recorded a strange signal appearing to have emanated from a Sun-like star some 95 light-years away. Photo Credit: Special Astrophysical Observatory

On Aug. 27, it was reported a strange signal appeared to have emanated from the vicinity of a Sun-like star almost 95 light-years away. The star is known as HD 164595 (also HIP 88194). The news was broken by Paul Gilster on the Centauri Dreams blog, the official forum of the Tau Zero Foundation (TZF), which is dedicated to the reporting, study, and promotion of interstellar flight and exploration.

Although the signal from HD 164595 was detected back on May 15, 2015, by a team using the large RATAN-600 radio telescope in Zelenchukskaya, in the Karachay–Cherkess Republic of Russia (near the border with Georgia in the Caucasus), Gilster had only just recently learned about this discovery from a member of the discovery team.

“Claudio Maccone, an old friend, is one of the scientists involved with the RATAN-600 work,” Gilster told SpaceFlight Insider. “He sent out an email to most of the SETI community [about HD 164595] and kindly included me in it.”

The signal from HD 164595

The signal from HD 164595 as recorded at the RATAN-600 radio telescope. It shows a large spike, lasting some 4 seconds, raising well above background noise. Credit: Bursov et al

Gilster then wrote back to Dr. Maccone and asked him if the information was meant to be public.

“He told me it was, and that this was the announcement, so I was free to write it up,” Gilster said.

Gilster said the reason why the signal drew such professional attention was because it was “a strong transient signal,” similar to the now legendary “Wow!” signal detected in August of 1977 by the now dismantled Big Ear radio observatory at Ohio State University.

“The fact that it rises so high above the background noise is interesting, but not necessarily definitive,” Gilster said. “The question then becomes, ‘is there a local source that could account for this, like a satellite overhead or something of that nature?’ The [Russian] team clearly thinks this is an unlikely possibility, but it has to be investigated. Also, [astronomer] Jean Schneider is studying this to see if a microlensing event might have occurred involving this star.”

Gilster said Schneider, who works at the Paris Observatory and has maintained the Extrasolar Planets Encyclopaedia since early 1995, is investigating the possibility that HD 164595 is a microlensing event. However, Schneider has not yet told Gilster how strong the evidence for this is.

“We should be able to work this out if we can work back to what stellar occlusions might have occurred in the time frame involved,” Gilster said. “In other words, did the target star move in front of a more distant target that could have produced a lensing event. I don’t know the time frame for Dr. Schneider’s work, but it will be fascinating to see what he uncovers.”

As for other possibilities regarding this “alien” transmission, Gilster said astronomers have to consider things such as a local terrestrial signal.

“It’s always possible, if the signal never repeats, that we won’t know the answer,” Gilster said. “This could be consistent either with a non-repeating local event or with a ‘Benford beacon’: In other words, a distant interstellar beacon that happens to sweep over us and that we don’t notice again because the time between receptions is so long (and we may not be looking).”

This rather large gap in time between the discovery of the signal from HD 164595 and its announcement to the wider community over one year later has frustrated many professional scientists as well as the general public over the potentially lost opportunity to determine the true nature of the enigmatic signal.

Franck Marchis, a senior scientist with the SETI Institute in Mountain View, California, and the organization’s Exoplanets Research Thrust Chair, wrote in his blog that, “although international protocols call for alerting the astronomical community to the detection of a mysterious signal, the observers [at RATAN-600] chose not to do so. Sadly, their failure to observe this simple protocol likely hindered our ability to clarify exactly what caused the signal.”

Wow! signal

In 1977, astronomer Jerry Ehman discovered this signal a few days after the computer recorded the data. He was so impressed when reading the results, he circled the letters and wrote “Wow!” The signal, which spanned 72 seconds, has not been detected since. To date, astronomers have not agreed upon the exact origin or nature of the source. However, it is considered the best candidate ever received for an alien transmission. Photo Credit: North American AstroPhyscial Observatory

Despite the length of time between the discovery of the HD 164595 signal and its revelation to the rest of the world, several SETI facilities have already begun to examine that distant star to see if the signal might return.

The SETI Institute began listening for the signal to repeat the day after its announcement with the 42 radio dishes that comprise their Allen Telescope Array (ATA) at the Hat Creek Radio Observatory in California.

Meanwhile the team at the Berkeley SETI Research Center that is part of the Breakthrough Initiatives effort have also scanned HD 164595 with their back-end instrument at the Green Bank Telescope (GBT) in West Virginia – the same facility where the first modern SETI, Project Ozma, occurred in 1960.

The Berkeley team has already published a preliminary report  in which they stated their GBT observations did not detect any ongoing emission from the direction of HD 164595. According to the report, single-epoch transients are by their nature hard to confirm or deny, illustrating the need for confirming follow-up, either at a later time, or as part of the observing strategy.

Scanning radio frequencies are not the only means by which HD 164595 will be examined. Doug Vakoch, the President of METI International (Messaging Extraterrestrial Intelligence) told Universe Today his organization will be looking for brief laser pulses using the Boquete Optical SETI Observatory in Panama just as soon as meteorological conditions improve there.

The team that made the discovery at RATAN-600 last year will be presenting further details on their findings with HD 164595 at a meeting of the IAA SETI Permanent Committee, to be held during the 67th International Astronautical Congress (IAC) in Guadalajara, Mexico, Sept. 27, 2016.

Gilster said he thinks the public should understand signals like this aren’t necessarily rare, because SETI scientists have seen other transient signals that never repeated and could not be identified.

“These, we assume, were some local signal that was picked up, and this may be the same scenario,” Gilster said, “But I take the RATAN-600 team at their word that they believe the odds on that are slim.”

Gilster does admit he has yet to see the paper the Russian team will submit next month, so he does not know exactly what they are basing their claim upon. However, he does assume it will be revealed next month to an eagerly awaiting world.

“I think this is an ‘interesting’ detection,” Gilster said, repeating what he wrote in his original Centauri Dreams article. “It does not mean we have detected an extraterrestrial civilization. But it does merit further study.”


Larry Klaes is an author and freelance journalist specializing in news and educational work on the sciences. Klae's past endeavors include editor of SETIQuest magazine and President of the Boston chapter of the National Space Society (NSS). Klaes joined SpaceFlight Insider in 2016.

Reader Comments

Marlene E. Arenas Fierro

We are not along!!! Second WOW!, I hope don’t dismantle the radio telescope this time and continue research this star. Great!

Objects such as these should get high priority if any strange signal is detected even if it is to rule out instrumentation issues or signals terrestrial in nature.

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