Enjoying EarthSky? Subscribe.

224,155 subscribers and counting ...

No alien signal, says SETI astronomer

A strong signal from a sunlike star sparked speculation this week that we might – at last – have heard from an alien civilization. Now astronomers say … no.

You might have read the stories this week about Russian astronomers detecting a possible “signal” from a star 94 light-years from Earth. The signal from sunlike star HD 164595 – said to be a very strong signal – spawned a flurry of speculation that, maybe, perhaps, at last, we’ve heard a signal from an alien civilization. In the video above, though, Seth Soshak of the SETI Institute says the signal has now been identified as being from a Russian military satellite.

Astronomer Yulia Sotnikova wrote in an update published today – August 31, 2016 – by the Special Astrophysical Observatory of the Russian Academy of Sciences:

Subsequent processing and analysis of the signal revealed its most probable terrestrial origin. It can be said with confidence that no sought-for signal has been detected yet.

Like many other stars in our Milky Way galaxy, the star HD 164595 looked promising as an abode for alien life. Italian astronomer Claudio Maccone and others had described it as:

… a strong candidate for SETI.

What did SETI astronomers think the signal might be?

If the signal had been artificial, its strength suggested that it came from an advanced civilization, at least a Type II on the Kardashev scale, which astronomers have been talking about and speculating about for decades. The Kardashev scale – originally designed in 1964 by the Russian astrophysicist Nikolai Kardashev – is a lot of fun to think about. It’s a way of imagining a civilization’s level of technological advancement, based on the amount of energy it’s able to harness.

We humans on Earth, for example, represent a Type I civilization – sometimes called planetary civilization. We have the technology to use and store energy from our sun that strikes our world’s surface, or nearby space.

A Type II civilization can do much more. It has the capability to harness the energy of the entire star. The device used to do this is called a Dyson sphere. It’s basically a big sphere built around a star that can capture its energy. Read more about Dyson spheres here.

As early as yesterday, those with technical backgrounds were already urging caution on the idea that the signal apparently from HD 164595 was a sign of aliens. On the website SETI@home, someone (apparently an astronomer) commented:

I was one of the many people who received the the email with the subject ‘Candidate SETI SIGNAL DETECTED by Russians from star HD 164595 by virtue of RATAN-600 radio telescope.’ Since the email did come from known SETI researchers, I looked over the presentation. I was unimpressed. In one out of 39 scans that passed over star showed a signal at about 4.5 times the mean noise power with a profile somewhat like the beam profile. Of course SETI@home has seen millions of potential signals with similar characteristics, but it takes more than that to make a good candidate. Multiple detections are a minimum criterion.

Because the receivers used were making broad band measurements, there’s really nothing about this “signal” that would distinguish it from a natural radio transient (stellar flare, active galactic nucleus, microlensing of a background source, etc.) There’s also nothing that could distinguish it from a satellite passing through the telescope field of view.

And so it is a satellite. To all SETI astronomers: keep searching!

Bottom line: A strong signal from sunlike star HD 164595 sparked a flurry of speculation this week that we have – at last – heard from an alien civilization. Now astronomers say the signal was from a military satellite.

Deborah Byrd