Just a little news tidbit I thought I’d slip in between the more important stuff, like Jeb Bush’s third-quarter fundraising haul and whether that aunt who sued her nephew has hugged it out with him yet.
You are much, much better off using the time you’d devote to reading this post to reading someone else’s far more intelligent treatment of the subject instead. In particular, I’d recommend Slate, The Atlantic, and, for a more skeptical view, the New Scientist. Since clicking a link is too much effort for some readers, though, here’s the bottom line. A long time ago, in a galaxy far, far away (actually, it’s our galaxy, but whatever), roughly 1,481 light years from Earth, something strange started happening to a star known as KIC 8462852. You can’t see it with your naked eye; we know it exists only because the Kepler Space Telescope picked up the light coming from it, along with light from many thousands of other stars. One way astronomers can tell if there are planets orbiting a distant star is by tracking the brightness of the light the star emits. If a star’s light dims a tiny bit at regular intervals, that’s evidence that something is passing between it and the telescope. For a star the size of KIC 8462852, which is around one and a half times as big as our own sun, having a planet the size of Jupiter pass in front of it should dim the light by around one percent.
Since scientists began watching KIC 8462852, they’ve found that its light does dim — but not at regular intervals. And it doesn’t dim by one percent. It dims by … 15 percent. And 22 percent. The dimming doesn’t happen symmetrically, with a slight, gradual fade followed by a slight, gradual brightening. It can dim slowly and then rapidly brighten. Per Slate, “There’s also an apparent change in brightness that seems to go up and down roughly every 20 days for weeks, then disappears completely.” This is not the way stars normally behave. In fact, after having looked at thousands of other stars captured by the Kepler, this is the only star known to astronomers to behave this way. They’ve rechecked their data to see if there’s an error in the math or some sort of flaw in the lens, but if there were, you would expect to see the same sort of error in other stars’ measurements. Again: This is the only star that seems to operate this way.
One possibility is that it’s a young star, (relatively) recently formed, with lots of dust and debris still circling around it in the aftermath. That would explain the irregular dimming — except that the dust that surrounds young stars typically leaves a signature of infrared light, and KIC 8462852 doesn’t have that. Same goes for the idea of a nearby planetary collision. Lots of dust should mean lots of infrared reflections, but KIC 8462852 is emitting just the right amount of infrared light you’d expect from a normal star its size. The working hypothesis for now on what’s behind the strange dimming phenomenon is that it’s actually an enormous swarm of comets that were somehow sucked towards the star, possibly by the gravitational pull of another nearby star in transit, and are now burning off like fireworks all around it. That would explain the irregular, unpredictable dimming coupled with the lack of elevated infrared. The New Scientist explains:
Having worked through the other possibilities, the team concluded the most likely explanation is a family of exocomets that veered close to the star and were broken up by its gravity, producing huge amounts of dust and gas in the process. If the comets are on an eccentric orbit passing in front of the star every 700 days or so, further breaking up and spreading out as they go, that could explain all the dips in the data.
KIC 8462852 is about 50 per cent larger than our sun, so if this comet explanation is correct, the dust cloud would be pretty big. It would be an impressive sight up close, says Boyajian. Something that size in our solar system would blot out a significant amount of sunlight. When Earth passes through the debris clouds left in interplanetary space by passing comets, we get meteor showers. There’s no evidence of a planet in the KIC 8462852 system, but someone standing on such a world as it passed through the dust cloud would see quite a light show, says Boyajian. “The scale of the meteor shower would be huge, like cosmic-scale fireworks.”
Here’s where a more intelligent commentator would be useful because I don’t understand why the dust generated by an enormous storm of comets disintegrating around the star wouldn’t also generate an elevated infrared reading. I’m also having trouble conceptualizing the scope of a storm that could dim the light of the star by 22 percent when a mass the size of Jupiter could only manage one percent. And scientists have another problem with the theory: It seems remarkably coincidental that KIC 8462852 would be in the process of devouring a massive comet cluster just at the moment that we happened to point our telescope at it — the blink of an eye cosmically. How long would the heat and gravity from the star realistically take to suck a belt of comets into it? And we somehow caught that on the Kepler, in progress, in the few years that the telescope was functioning properly? That’s some luck.
Which brings us to the other theory. The Atlantic:
Jason Wright, an astronomer from Penn State University, is set to publish an alternative interpretation of the light pattern. SETI researchers have long suggested that we might be able to detect distant extraterrestrial civilizations, by looking for enormous technological artifacts orbiting other stars. Wright and his co-authors say the unusual star’s light pattern is consistent with a “swarm of megastructures,” perhaps stellar-light collectors, technology designed to catch energy from the star.
“When [Boyajian] showed me the data, I was fascinated by how crazy it looked,” Wright told me. “Aliens should always be the very last hypothesis you consider, but this looked like something you would expect an alien civilization to build.”
The theory, in other words, is that the energy from KIC 8462852 is being harnessed by some sort of planetary-sized structure of solar panels or something akin to that — a “Dyson sphere,” named after Freeman Dyson, who imagined that alien civilizations would figure out a way to satisfy their energy needs by milking local stars for it. A star’s just a big nuclear reactor, right? Might as well hook up some power lines to it and enjoy the juice. How a Dyson sphere would explain the data from this star isn’t clear to me, except as the end of a “no other theory works” process of elimination. Any sort of technology we can imagine, however massive, that’s pumping energy from KIC 8462852 would be in orbit around it, no? That means, I would think, that we should be seeing regular dimming intervals, not irregular ones, as the Dyson sphere transits around the star. The answer to that, I guess, is that maybe the dimming isn’t the product of a shadow passing in front of the star but the star itself actually temporarily losing luster as energy is drained from it, like the lightbulbs in a home momentarily dimming when there’s a sudden surge of demand on the grid. That’s hard to conceptualize too, but that’s the beauty of this theory, I guess. Whatever’s happening is so freaky deaky weird that you can indulge whatever flight of fancy you like in imagining how this technology would work. Who knows? Maybe it’s a giant Death Star and dims whenever it’s firing at Alderaan or whatever the aliens’ latest target is.
The Kepler telescope no longer works so astronomers don’t know what’s been happening with KIC 8462852 lately. The next step now is to point a giant antenna at the star and see if any unusual radio signals come back. If they do, hoo boy.