字幕表 動画を再生する 英語字幕をプリント You might remember that almost exactly a year ago, there was a lot of buzz about one particular star. There were strange signals coming from this star, and no one was exactly sure what was causing them. Some people were even saying that the signals could have been caused by an alien civilization. Well, last week, the story got even weirder. Because not only does the star’s light flicker unpredictably, but it’s been getting dimmer over time. This star’s called KIC 8462852, and it’s been nicknamed Tabby’s star after Tabetha Boyaijan , the scientist who described its weird properties — and who Hank interviewed on SciShow in August! Tabby’s star caught the attention of astronomers after it was observed by the Kepler telescope’s exoplanet-hunting mission. Kepler spots exoplanets by watching for stars to dim slightly as a planet passes in front of them. Most planets that it spots do this regularly, once every revolution around the star. But, Tabby’s star is different. Its light dims unpredictably, at irregular intervals, and scientists aren’t sure why. The most likely explanation is that a comet has recently broken up in front of the star, and dust and chunks of debris are obscuring our view at random. The far less likely, but way more awesome, explanation is that an alien civilization is using some kind of huge structure to harness the star’s energy. Astronomers have been scratching their heads ever since this phenomenon was announced last year. Then, in January of this year, another researcher announced that Tabby’s Star has gotten dimmer overall since 1890, based on old photographic observations. But, as you can probably imagine, data collecting methods have changed a little since the nineteenth century, and comparing old photographic plates to new digital data could introduce some errors. In a paper being published by The Astrophysical Journal, researchers at Carnegie and Caltech checked into this claim using more recent data: the observations from Kepler over the course of four years. Kepler would check in on the star every now and then to look for changes in its light. Plus, because of the way Kepler works, it has to make a lot of observations to calibrate the camera and get a complete picture. So there are lots of observations made by the same instrument. The results were surprising. Tabby’s star is dimming over time, the researchers say. Over the first three years of Kepler observations, it got darker by one percent. That might not seem like much, but stars are huge, so that amounts to a whole lot of energy. Then, in the next six months, the star’s brightness plunged by two percent, before leveling off for the rest of the observation period. A few of the other stars in Kepler’s dataset got a little dimmer over the same period, but not so much or so quickly. If the star had only dimmed in the past six months, a comet or planet breaking up would fit the data really well. But four years of dimming is harder to explain — and the dimming might go all the way back to 1890! We’ve never seen another star act this way, and we don’t have a good explanation for it. And another space news closer to home, Blue Origin, the spaceflight company run by Amazon CEO Jeff Bezos, has pulled off a pretty cool flight test — and it went way better than they expected. Blue Origin’s New Shepard launch system consists of a crew capsule sitting on top of a booster rocket. And both the capsule and booster are built to be reusable. On October 5th, New Shepard passed a crucial test. The flight was aborted — on purpose — partway through launch. That meant the crew capsule fired an engine to separate itself from the booster. Blue Origin intentionally picked a time, 45 seconds into the flight, where the spacecraft would be most difficult to control. The capsule used parachutes to land in the Texas desert, and it was recovered safely, which means the crew of a launch system like this could probably survive an accident mid-launch. As an added bonus, the booster survived too, and it wasn’t really expected to. Blue Origin predicted that the capsule’s escape motor would send the rocket into a death spiral. Which is an acceptable loss, when you’re trying to save the crew. But the booster was fine, and came back to land on its pad like nothing was wrong. So, with five successful tests in less than a year, Blue Origin seems ready to get off the ground. As for New Shepard, it’s flown five successful test missions and will now be retired. It’s done its job of proving that Blue Origin can build a rocket that works, is reusable, and can pass safety tests. But it was also only meant for short flights that don’t achieve Earth orbit. The next planned spacecraft, New Glenn, will have a lot more power under the hood. It’s designed to be capable of orbital flight. And they plan to make even bigger rockets after that. Crewed Blue Origin test flights could happen as early as next year, and the company eventually plans to take private passengers, too. No word yet on how much a ticket will cost, but you might want to start saving up. Thanks for watching this episode of SciShow Space News, and thanks especially to our patrons on Patreon who help make this show possible. If you want to help us keep making episodes like this, you can go to patreon.com/scishow. And don’t forget to go to youtube.com/scishowspace and subscribe!