字幕表 動画を再生する 英語字幕をプリント There's an unsolved mystery out there in space. One of many, to be sure, but this is one that some people really want to blame on aliens because we haven't had a stronger explanation. I'm talking about Boyajian's star, or KIC 8462852 and some new observations that may have just given us the information we need to say with certainty: Aliens!? Or no? Boyajian's Star, previously referred to as Tabby's star, is named after the astrophysicist who first studied its inexplicable behavior. It's a bit larger than our own sun, and is about 1300 light-years away. And it displays behavior that we just can't figure out. Actually, it's the most unusual dimming of a star ever observed. Its brightness dips in totally erratic and unpredictable ways. Sometimes just a tiny bit, sometimes by as much as 22 percent. And here's the thing—these behaviors can't be attributed to most of the things you would think of. The dimming is much too substantial to be caused by an orbiting planet, because even planets as big as the biggest ones in our solar system would only make a tiny blip in the brightness of Boyajian's star. Plus, if it were a planet, we should be seeing the same dip in brightness at regular intervals as the planet runs rings around that star, but no. Maybe it was a swarm of comets careening toward the star. But then astronomers found that the star actually has been dimming steadily for years in addition to the unpredictable blips in brightness—it's losing its shine, and it's about 14% less bright than it was a century ago. A comet cloud couldn't cause something that gradual. So the lack of any convincing explanation for its finicky behavior is what gave rise to this idea of energy-generating alien technology, like a Dyson sphere, which I think is pretty hilarious. It is indeed very tempting to think that the unpredictable dimming of this star is due to some alien megastructure passing in front of it to gather power. But a new model from Columbia University may just give us an answer that doesn't rely on the existence of a hyper-developed solar-powered alien civilization. The new theory says that maybe Boyajian's star has been a little bad. Like the villain in a Charles Dickens novel, it may have stolen an orphaned exomoon. This hypothesis is based on the idea that the star pulled a moon into its orbit from a now long-gone planet, and the poor moon is now being torn apart by stellar radiation that it wasn't used to in its previous life, orbiting merrily around a planet. The resulting plumes of debris from the moon's outer layers blow off into the solar system, coming in between the star and Earth, causing—from our perspective—the occasional, unpredictable dips in brightness. But what makes this theory so tantalizing is that it also explains the gradual wane in brightness. As more and more of the moon breaks up, the larger, heavier chunks are getting pulled into orbit with what remains of the original exomoon. This forms a disk of debris that sticks around, dimming the star's light over time. Using models of both exomoon detachment dynamics and obscuration of stellar light, the team has compiled some pretty convincing evidence for this hypothesis—and it's certainly at least a little more credible than the idea of alien technology. But we still need a bigger sample size to come to any hard conclusions And we're in luck, because it turns out—Boyajian's star has friends! A new study surveyed more than 14 million stellar objects, and found 21 stars that also might display unusual, unexplained dips in brightness. The hope is that this data will allow us to study these bodies, and look for clues to see if the same mechanism is behind each of their blinking and winking, and if so, if it just might be this orphaned exomoon theory. That sounds like a pretty cool job. If you want even more on some crazy behavior of stars that we're just beginning to uncover, watch this video here, and subscribe to Seeker for all your stellar exploration news. Let us know what other space mysteries you want us to cover in the comments below, and as always—thanks for watching.