There’s something strange going on in orbit of the Kepler star KIC 8462852. As has been extensively covered elsewhere, the star suffers from some unusual obscuring sources which do not have ready explanations.
Of course, this has excited a great deal of speculation, ranging from everything from the reserved (Mysterious Star Leaves Scientists Wondering What’s Passing in Front of It) to the more prosaic (The Most Mysterious Star in the Galaxy) to the downright fanciful and inaccurate (NASA’s Kepler Telescope discovers a Colossal Artificial Structure Orbiting a Star in our Vicinity) to the incredibly misleading speculation of Michio Kaku. There’s at least three parody twitter accounts (probably run by astronomers, because we’re a cheeky sort) claiming to be the superintelligence responsible for building the structures.
But what is going on?
First off, let’s look at what we actually know about the star.
Kepler observed this star every 30 minutes for its entire prime mission, just over 4 years. During that time, the star was dimmed a number of times. Normally, for Kepler, these events are binary stars eclipsing each other, disks eclipsing the star, fluctuations from variations in the star itself, or planets transiting the star – anything that would remove some of the light received by Kepler.
In this case, there are a LOT of dipping events going on, (see the graphs on Page 3 of the PDF, if you’re interested) all of different depths, and not as regular events. This is something computerized Kepler planet searches couldn’t, and didn’t find. It was found by ordinary citizens looking through Kepler lightcurves with the Planet Hunters project. After it was found, astronomers made a special search of every other star observed by Kepler, and this is the only one that does anything like this. This star is downright RARE.
Here are some things considered by Tabetha Boyajian and her co-authors:
* It’s some crazy kind of variable star, where all the variation in light is because of the star itself. However, it doesn’t look like any kind of variable star we’ve ever heard of before. It really does look like some object passing in front of the star.
* It’s a whole flotilla of planets orbiting the star. It’s difficult to see how to pack them all in such that they wouldn’t crash into each other, but there are actually two stars in the KIC 8462852 system – one is a bright F3 star (30% larger than the Sun and 5 times brighter), while the other is an M dwarf, which is less than half the size of the Sun and much dimmer… the M dwarf can’t be the source of the largest dip (it would have to go to less than zero brightness), but at least SOME of the objects could be orbiting it.
However, not all the objects are symmetrical in-out curves you’d expect from a spherical object like a planet. Some look like a small object transiting, followed by a big one, then a smaller one again.
* It’s something not round orbiting the star, like a giant dense dust cloud or a debris cloud from a planetary collision. They would have to be DENSE and HUGE, and very very recent. That sounds like incredible luck, but KIC 8462852 is genuinely unique, so maybe we ARE that lucky.
* It’s a cloud of dust surrounding new planets that are forming. That’s possible, but we’ll need some observations to look for dust in the system, and at the distance of KIC 8462852 that’ll be difficult.
* It’s a family of giant comets, whose tails are somehow big enough AND dense enough to blot out the star to that extent. That’s also difficult, because comet tails can either be big enough or dense enough, but not both.
It’s not in the paper, but I throw out another idea here:
* It’s something between us and the star, either a series of clumps of dust in interstellar space, or the remains of a recently disintegrated object in our own Oort cloud where all the fragments are flying in front of this star. Sure, the alignment has to be INCREDIBLY precise, but again this is the only Kepler star that does this, so it CAN be an incredibly unlikely thing.
And then (not mentioned at all in the paper) there’s aliens. Sure, it could be (maybe the Death Star just blew up a planet) but astronomers have been burned before. Pulsars? Not signals from an alien civilization, just rapidly spinning neutron stars. Gamma Ray Bursters? Probably actually high-mass supernovae. Perytons? Microwave ovens reheating the observers’ meals. The “Wow!” radio signal recieved in 1977? …well, I have no idea on that one. The explanation for KIC 8462852 is certainly going to be unusual, but I seriously doubt it’ll be worthy of the X-Files. Maybe NOVA.
But, there’s this paper: The Ĝ Search for Extraterrestrial Civilizations with Large Energy Supplies. IV. The Signatures and Information Content of Transiting Megastructures. We do after all want to find aliens if they ARE out there. That’s in NASA’s mission statement, after all.
For the moment, all we know is that some thing or things are dimming KIC 8462852. To quote Sir Arthur Conan Doyle: when you have eliminated the impossible, whatever remains, however improbable, must be the truth. We haven’t eliminated much of anything, so it’s definitely not time to move into the improbable. It’s not proof of an alien civilization, it’s not proof of gigantic solar-system-sized construction… it’s not proof of ANYTHING yet.
Two weeks ago I talked about the long history of NASA confirming surface water on Mars, which ultimately illustrates that good science takes time. This is also going to take time. There are going to be lots of observations of this star in the next few months and years, so we should know more soon.
I’m not saying it’s not aliens, but it’s not aliens.