KIC 8462852 The Alien Megastructure Star

Much ado was made at the end of 2015 over a strange star known as KIC 8462852 or "Tabby's Star" after Dr. Tabitha Boyajian, one of the scientists investigating it. The mystery began when a group of citizen scientists known as "The Planet Hunters" were looking at light curves taken by the Kepler spacecraft in 2011. Within these light curves, the planet hunters can see dips in brightness that happen when a planet moves in front of its parent star blocking the light just a little bit. This is how hundreds of exoplanets were found using Kepler, which is remarkable in and of itself. However, one light curve looked very, very strange. Like unprecedented strange.

Within the light curve of Tabby's star, enormous multi-day dimming events were apparent where very large objects or swarms of objects were seen passing in front of the star blocking as much as 22 percent of its light. Compare that to our solar system where at the same distance gigantic Jupiter would block only about 1 percent of the sun's light. Something very large indeed was blocking the light from Tabby's star.

In their original paper, Boyajian and her colleagues concluded that very few natural phenomena could be responsible for that amount of blocked starlight, and none of those explanations fit very well with what they were seeing in the light curve. Ultimately, they concluded that the most likely explanation was a swarm of comets breaking up causing the light to dim from dust and gas. This, however, was not a great explanation, merely the best plausible one. Then, Jason Wright at Pennsylvania State university offered another possibility: that the light was being blocked by gigantic alien megastructures.

That may sound like far-fetched science fiction, but in reality it's not. An object called a Dyson sphere was cited as one possible type of megastructure that might fit the bill. A Dyson sphere, or more probably a Dyson swarm, could be built by an advanced alien civilization to harvest solar energy from their star. We ourselves are already starting our  own primitive Dyson swarm in the form the multitude of spacecraft in solar orbit that we have launched over the decades, so the idea is not that much of a stretch for a civilization considerably older and more advanced than our own. The trick however, is in catching them in the act of having the sphere. The odds are likely low that we would just happen to be looking at just the right moment in time to catch a glimpse of a Dyson sphere due to the relatively short window in geologic time that such a thing might exist. This part of the story has recently become even more complicated because there may be indications that if it is a Dyson's Sphere, it is currently under construction. More on that in a minute.

In an attempt to resolve the question, SETI radio astronomers pointed the Allen Telescope Array towards Tabby's star to look for radio and laser emissions. They saw nothing. But that may not mean too much. The result is not all that surprising, given that Tabby's star is 1,480 light years away which would require extremely powerful radio transmitters pointed directly at us for us to hear them. It seems unlikely that an advanced alien civilization would do that on purpose unless they wanted to contact us. But given the distances, they have no way of knowing that we are here. From their perspective they see us 1,480 years in the past, about the time when the western Roman Empire had just fallen. That was long before anyone here emitted any radio waves for the aliens to pick up. And, of course, there's no guarantee that an alien civilization would care to contact a civilization far more primitive than their own.   

It was at this point that the story began to lose the media's attention. But the story did not end there and several intriguing new developments have come out over the last few months. It came in the form of a paper by Dr. Bradley Schaefer of Louisiana State University. Using photographic plates from Harvard that were taken over the course of a century, he discovered that Tabby's Star not only dims periodically, but has been dimming overall for over a century. This is a very short time for a star of this class to dim as much as it did. Stars like this dim over timeframes of millions of years, not hundreds. He concluded that the unprecedented long-term dimming that he observed, and the light curve dips seen by Kepler must be due to the same phenomenon when Ockham's razor is applied. For this to be a phenomenon related to a group of comets, he calculated that it would require 648,000 giant comets orchestrated to pass in front of the star in order to explain the century long trend. That is considered to be implausible. Whatever this is, it doesn't appear to be due to a swarm of comets.

The second development was known about but not well talked about in the media when the story was hot. It involves a specific feature within the Kepler light curve that presents an interesting mystery. Around day 800 during Kepler's run, a single, large dip occurred over several days that presented very smooth geometry. While this could be interpreted in several ways, one of the ways is that a giant isosceles triangle passed in front of the star.

This is interesting for those willing to entertain the possibility of alien megastructures. It has been suggested that the easiest way to announce to the universe that you exist is not by building huge radio beacons, those require incomprehensibly massive amounts of energy, but instead constructing a huge object, like a baffle, perhaps out of Mylar or a similar material, in such a shape that is not possible in nature. Then you make it pass in front of your star and then anyone with a Kepler spacecraft can see it. A triangle might be one such shape. It's worth noting though that comets are isosceles triangle shaped, but there's a catch, to make this particular signature in the light curve, the comet's tale would have to be pointing towards the star. Very odd, but not impossible, in fact the original Boyajian paper gives an explanation for how that could happen, but this new comet implausibility issue may call that into question and that certainly deepens the mystery.

But then we run into problems with the alien megastructure idea. While I consider the megastructure hypothesis unlikely, I am a science fiction writer rather than a scientist so I'm allowed to speculate a little more than they can. The amount of dimming Schaefer observed is very significant, about 20 percent over a century. That's a lot. For an alien race to create structures that rapidly in order to account for the overall dimming trend, they would have to be in one serious rush. To a point that it seems impossible. But maybe not, at least if you're willing to entertain ideas of future technology.

Building giant objects very rapidly might eventually be possible through the use of self-replicating nanotechnology. Evoking the Grey Goo, a single self-replicating nanobot could in theory exponentially reproduce like a virus and consume the entire mass of the earth within two days. That's a lot of work over a short time. Needless to say, nano-technology theoretically can also build things very rapidly. But to create megastructures of this apparent size that block that much light would require enormous amounts of matter. Think completely disassembling the planets in your solar system amounts of matter. So is it possible that an alien civilization is constructing a Dyson's swarm very rapidly using nanotech? Well, yeah, possibly. Or the phenomenon behind Tabby's star could just be a wild goose chase with a natural explanation that we haven't thought of yet. Only time will tell.

So there you have it, that's where the Tabby's Star story is as of April 11, 2016. What could be the biggest news story in centuries is still ongoing, with the possibility of alien megastructures still not discounted. Of course, it could still get discounted, and very probably will, but for now this is the most tantalizing hint we've ever seen that we are not alone, even more so than the famous 1970's Wow! signal of SETI fame.