Most of the time, stars are pretty predictable. Our telescopes plot their brightening and dimming, usually caused by periodic planetary transits, without too many erratic deviations from the norm.
But KIC 8462852 is different. This star is more massive, hotter, and brighter than the Sun. It’s about 1,500 light-years away—and NASA’s Kepler space telescope has seen some pretty weird data coming from it. There are huge, irregular dips in the light, sometimes dropping up to 22%.
Here’s Phil Plait, writing for Slate:
Straight away, we know we’re not dealing with a planet here. Even a Jupiter-sized planet only blocks roughly 1 percent of this kind of star’s light, and that’s about as big as a planet gets. It can’t be due to a star, either; we’d see it if it were. And the lack of a regular, repeating signal belies both of these as well. Whatever is blocking the star is big, though, up to half the width of the star itself!
Also, it turns out there are lots of these dips in the star’s light. Hundreds. And they don’t seem to be periodic at all. They have odd shapes to them, too. A planet blocking a star’s light will have a generally symmetric dip; the light fades a little, remains steady at that level, then goes back up later. The dip at 800 days in the KIC 8462852 data doesn’t do that; it drops slowly, then rises more rapidly. Another one at 1,500 days has a series of blips up and down inside the main dips. There’s also an apparent change in brightness that seems to go up and down roughly every 20 days for weeks, then disappears completely. It’s likely just random transits, but still. It’s bizarre.
The problem, though, is that KIC 8462852 doesn’t seem to radiate an excess of infrared. Plait writes that if the mini-transits are being caused by scattered planetary collisions, we’d see the extra warmth from those impacts in the infrared, too. And so far, astronomers have ruled out several other possibilities, including a theory that a nearby red dwarf star is warping KIC 8462852’s Oort cloud—an icy region at the edge of a solar system—and sending comets screaming toward the sun. (Though Plait says that idea is still plausible and worth looking into further. Be sure to check out Plait’s article if you want to read his detailed analysis.)
So what else could explain such peculiar data? Enter Dyson spheres. They’re basically like solar panels, but in space.
Kate Becker, editor of NOVA’s Nature of Reality blog, wrote about Dyson spheres in May:
In 1937, the science fiction writer Olaf Stapledon imagined […] an enormous, spherical solar collector, built to encircle an energy-hungry civilization’s home star like a giant mylar balloon. This hypothetical mega-structure would grab every last photon of sunlight, providing enough energy to run whatever future technologies engineers could dream up. In 1960, physicist Freeman Dyson fleshed out the scheme: instead of a giant balloon, he speculated, an advanced civilization might crumble up its solar system’s uninhabited planets to create a swarm of rocks that could gather solar energy more efficiently. Dyson also pointed out that, if such a sphere or swarm existed, it would look to us like an unusually dark star, radiating waste heat in the infrared.
Even though idea originated in science fiction, it has real-life merit. Becker points out that a handful of scientists are going so far as to propose the existence of different types of Dyson spheres. They could surround white dwarfs, or even rapidly rotating neutron stars called pulsars (if the civilization building it is sophisticated enough).
And huge solar panels could create the non-periodic dips we see in the star’s light.
Jason Wright, an astronomer who studies exoplanets, has published a paper in Astrophysical Journal calculating the physics of Dyson spheres. He and Tabetha Boyajian, lead author of the KIC 8462852 study, hope to use a radio telescope to watch for signals from the star. Keeping an eye on a particular star like this might be one of the best ways to narrow down the search for extraterrestrial life—that is, if the Dyson sphere theory is correct.