字幕表 動画を再生する 英語字幕をプリント You up for a little space adventure? Well, ok then, strap in! But today's destination won't just be a little cosmic pit stop – it could be your next home! Basically, astronomers have recently found a potentially habitable planet, but the key word here is “potentially” so don't go packing your bags just yet! This planet is called Barnard's Star B. (If you're wondering who Barnard is, I'll get to that a bit later.) Anyway, if you step on its surface, you'd probably see nothing around you except endless ice fields. Look up high into the dark sky, and you'll see a little murky-looking circle. No, that's not Barnard's moon – it's the planet's sun. Now look down. Deep under your feet lie countless rivers, lakes, and seas of liquid methane. Ok, time out. None of this sounds like something I'd call “habitable,” at least not for humans! So, that's it, there can be no life here. Case closed! Thanks for watching, remember to give this video a “like,” share it with your... Oh, I'm kidding! Give Barnard a chance, will ya? Hey, ya never know, he could be hiding a lot more life than you'd think in those rivers and seas of methane! Ok, back to our story. Let's explore that murky little circle that I told you was Barnard's sun, the one the planet is orbiting around. This star is only located 6 light-years away from us, and it's the 4th closest star to our solar system. Try to imagine our sun 5 times smaller and much less bright. Well, that's Barnard's Star for you, and it has some other absolutely unique properties. Believe it or not, it's the only star that bears the name of the astronomer who studied it. Now, let's meet him! Though Edward Emerson Barnard wasn't the first to discover this star, he proved in 1916 that it's the fastest star known to us. Yes, all stars are moving across the universe, but Barnard's Star is doing it at top speeds. And not only that, it's actually constantly approaching our solar system. Hey, don't worry – it won't cause any trouble to anyone! But one day in the next 10,000 years, it'll come closer to us than the Sun's current nearest neighbor-star: Proxima Centauri. Well, 10,000 years may sound like a lot, but in the cosmic scale of our galaxy, it's a mere moment, maybe two at the most. Barnard's Star is what astronomers call a red dwarf – a small, dim, and truly ancient star that's getting pretty close to the end of its life cycle. And, yes, Barnard's star fits the bill of a red dwarf. It's so ancient that it probably saw the birth of the Milky Way Galaxy itself. At around 10 billion years old, it's easily twice as old as our own Sun. For something normally as bright and heavy as a star, being small, dim, and super-fast is pretty remarkable! So it's no wonder Barnard's Star drew so much attention from astronomers. Ok, but what about all this talk of a habitable planet? I'm getting there! So, the first person to assume there was a planet somewhere near this star was astronomer Peter van de Kamp. Back in the 60s, he observed “wobbles” in the star's movement. So, wobbles = planet? Well, yeah, pretty much! You can even conduct your own little experiment and see for yourself. Try and lift something heavy in both hands, and spin it around yourself a few times as carefully as you can. You'll quickly notice that this object isn't the only thing that's moving – it'll move you too! Or at least it'll make you wobble a bit. The exact same kind of wobble is present when a star is spinning a planet around itself. Unfortunately for Peter van de Kamp, his observations were later proven to be flawed, but that doesn't mean he was completely wrong because there is, indeed, a planet around Barnard's Star! And we've now come full circle. Barnard's Star B was finally discovered on November 14, 2018. An international team of astronomers led by Dr. Ignasi Ribas from the Institute of Space Studies of Catalonia started their research 20 years ago when they observed Barnard's Star doing some other weird stuff besides wobbling. From time to time as it was moving across space, its light would change. It'd look kinda red one minute and then become bluish the next. Besides the whole wobbling thing, this kind of shift in starlight is another sign of an orbiting planet. They took lots of measurements with the most advanced astronomical equipment you could imagine, and they came out with 99% certainty that the planet Barnard's Star B exists. Now, it's considered to be a super-earth class planet. Sounds kinda epic, right? Something like Earth's cooler older brother, and that's not exactly wrong! Barnard's Star B has slightly more than 24 hours in a day, and it's always sunny there no matter what. And now it's definitely starting to sound like a better version of Earth! But “super-earth” is just the term astronomers use to describe only the size of a planet that's larger than Earth but considerably smaller than ice giants like Neptune. As for Barnard's Star B, it's about 3 times more massive than our planet. But it's nothing like it, and you already know that by now! Remember those seas of liquid methane? Yeah, it's all coming back to me! Anyway, besides that, this planet is a huge ball of rock and ice that lies beyond the habitable zone of its star. Even though it's closer to Barnard's Star than our Earth is to the Sun, its star provides only 3% of the light that our Sun does. (Remember, it's a small, dim, red dwarf.) And even if we still decided to meet “a new dawn for humanity” on this planet, there'd be one major problem: there wouldn't be a dawn at all! Barnard's Star is so dim that it barely lights up anything on the planet. And how would you feel about living in temperatures of -275°F below zero?! Well, that's the estimated average temperature on the surface of Barnard's Star B, so, grab your mittens! The only planet-like object in our solar system that resembles Barnard's Star B would be Saturn's largest moon: Titan. And that's exactly what makes the discovery of Barnard's Star B so exciting! Astronomers are really interested in studying Titan, and that's why they've become so enthralled by this new discovery. This planet, just like Titan, is partially composed of ice, which means that it has water. Of course, it's too cold for liquid water to be there, but it has its own forms of lakes, rivers, and oceans that you already know are liquid pools of methane. And according to a 2015 study at Cornell University, chances are that simple methane-based lifeforms can develop and survive in these conditions. So, in a nutshell, there could be something alive floating in a methane lake under the surface of an icy planet 6 light-years away from where you're sitting right now. Pretty cool, huh? But let's not forget that the existence of such lifeforms is pure theory. So the idea that this newly found Barnard's Star B planet is habitable for us humans is really far-fetched for now. But in the miraculous world of science, there's always room for new unexpected discoveries! Not to mention, even if Barnard's Star B isn't exactly a “swipe right” for us Earthlings, we've still got some other potential candidates. Actually, one of them is right in our neighborhood! Remember Proxima Centauri? Ya know, our Sun's closest neighbor-star? Well, it's got a planet of its own called Proxima Centauri B. (Lengthy name, but we can work on rebranding if we decide to move there!) This planet is actually pretty fascinating! It's slightly bigger than Earth, and it receives just enough light from Proxima Centauri to keep temperatures above 32°F. Although one side of the planet never sees starlight and the other is literally baked by its sun, the planet's equator could be quite livable, even for humans! So, would that make us Proxima Centaurians? Proxima Centauri Bees? Eh, like I said, we'll work out the details later! So, do you really think humankind will ever find a habitable planet to make our new home, or is this just the stuff of sci-fi movies? Let me know your thoughts down in the comments! And don't forget to give this video a “like,” share it with your friends, and click “subscribe” to always stay on the Bright Side of life!
B1 中級 米 NASAが驚きに満ちた新惑星を発見! (NASA Just Discovered a New Planet, Full of Wonders!) 148 3 Amy.Lin に公開 2021 年 01 月 14 日 シェア シェア 保存 報告 動画の中の単語