Alien Engineering Around Strange Star?

By Seth Shostak, Senior Astronomer

There's a new big dipper in the nighttime sky.

No, it's not a cozy constellation, but a distant, non-descript star that behaves like a shipboard semaphore, beaming flashes of light into the cosmic darkness that seem random, but may not be.

While the luminous output from everyday stars is relentlessly steady, this one occasionally dips its brightness as much as 20 percent, suggesting either that it is orbited by lumps of dust, rock or other opaque material, or - and hang onto your desk chair - there are residents in this stellar system who have deliberately built hardware of a size and extent big enough to intercept a substantial amount of their sun's output. In that case, what we're seeing is the consequence of a massive, alien construction project.

Seriously? Could this star, lovingly named KIC 846 2852 - a fairly ordinary stellar orb roughly half-again as big as our Sun and nearly five times brighter - be home to some advanced society that's solving its energy crisis by constructing what's called a Dyson sphere (or more practically, a Dyson swarm): a phalanx of solar panels that orbit their sun, turn oodles of starlight into electricity, and then beam that energy back to the home planet to power their fossil fuel-free lifestyle?

Well, that's certainly a possibility. The idea of Dyson swarms (first proposed by physicist Freeman Dyson) is appealing enough to have tempted several astronomers to look for them throughout the Galaxy. They've done so by searching for the warm glow of infrared light that would waft off the back side of the solar panels. Their task is tricky however, because any dust floating in the space between the planets (and there's always dust!) would mimic this infrared glow.

But KIC 846 2852 is different, because the evidence suggesting astroengineering is direct - there's a clear-cut and periodic dimming of the starlight - a much more straightforward observation than trying to tease out a foggy bit of infrared light.

Given this intriguing behavior, shouldn't we be checking out this star more carefully? Isn't it possible that this is a home to true cosmic intelligence - not just pond scum in the watery recesses of a nearby world, but technically adept beings who might have something interesting to tell us ... or at least spark endless conversation by becoming the first sentience discovered other than our own?

Of course. But history gently prods us to temper our enthusiasm by noting that the explanation for KIC 846 2852's inconstant glare might be prosaic, rather than profound. This star is one of the 150,000 stellar targets examined by NASA's Kepler space telescope. It was also one that was vetted in a citizen science campaign that used human eyeballs (as opposed to computer code) to hunt for unusual features. And indeed, what the humans found would likely have escaped notice by the software. The changes in brightness were highly variable and substantial, much as you might expect from a small swarm of moths attacking a street lamp.

The scientists who wrote the paper announcing this behavior gave their own take on what's going on here - their own explanations for what these "moths" might be. Clumps of dust are a possibility, as is natural variability of the star itself, or even errors in the data processing.

But none of these seem to cut the mustard. The discoverers prefer another explanation: A small star, now visible about 100 billion miles away from KIC 846 2852, recently made a closer pass, and disturbed some outer solar system comets. Much as lifting a rock sends sow bugs scurrying, the gravitational tug of this star could have prodded otherwise inoffensive comets to careen towards the inner regions of the KIC 846 2852 star system, filling it with debris that's causing the blinking.

That would be interesting, but obviously less exciting than finding a Dyson swarm. Still we must beware: Given our natural inclination to blame aliens for just about all unexplained phenomena on Earth, it's inevitable we'll give them credit even when they're not involved. Pulsars, when first discovered, were dubbed "Little Green Men" by Cambridge astronomers. They turned out to be dead stars. CTA 102 - a quasar discovered in the early 1960s, was seen to change its brightness very quickly, and at least a few Soviet astronomers figured that clever extraterrestrials were sending coded messages to whoever was paying attention. In fact, it turns out that quasars just naturally blink and for reasons that have nothing to do with intelligence.

In addition, KIC 846 2852 is hardly a star system anyone would finger as "most likely to house aliens." A few thousand degrees hotter than the Sun, this star would bleach the surface of any encircling planet with highly unfriendly ultraviolet light. In addition, it will take only 3 billion years for it to totally exhaust its natal supply of hydrogen fuel. It will die young. Keep in mind that it took 4-1/2 billion years for life on Earth to reach our own, modest technological level.

These are not show-stoppers: Maybe other planets can produce clever critters a lot faster than Earth did, and maybe the inhabitants are born with a number 50 sunblock epidermis.

And more generally, one shouldn't let healthy skepticism degrade into unattractive pig-headedness, even if in this case the evidence for something revolutionary isn't terribly promising. You have to follow up. And we are.

Since October 16, the SETI institute has been using its Allen Telescope Array to observe KIC 846 2852 over a wide range of radio frequencies (1 to 10 GHz), looking for any artificial signals. Keep in mind that this star system is relatively far, roughly 1400 light-years away. That's more distant than the Orion Nebula, and getting there (if you feel the need) would require a 23 million year ride in our fastest rocket. But more to the point, any signals detectable here on Earth would have to be exceptionally powerful.

We're continuing to analyze the data. In another week, our SETI team will once again observe KIC 846 2852 using some new receivers being affixed to the Allen Array - known as Antonio feeds - that will increase the sensitivity by a factor of two. Check this space.

Meanwhile, consider KIC 846 2852 as something suggestive of cosmic company, but no more than a suggestion.