Placeholder Image

字幕表 動画を再生する

  • [♪ INTRO]

  • There's been a lot of exciting asteroid news lately,

  • which is not exactly a sentence you hear very often.

  • First came an asteroid from somewhere else in the galaxy.

  • And just last week, scientists published their first detailed data

  • about the interstellar interloper.

  • Then there were the stories about a big asteroid called 3200 Phaethon,

  • which has an unusually small orbit and causes an unexplained meteor shower.

  • For some reason, most of those stories involved threatening headlines and graphics

  • suggesting that Phaethon will come frighteningly close to the Earth

  • and kill the dinosaurs... or something like that.

  • Which is a shame, because the truth is, as always, a lot more interesting.

  • But let's start with the interstellar visitor.

  • Scientists noticed it going way too fast to be orbiting the Sun back in mid-October,

  • and they realized that it came from outside the solar system.

  • Its name changed as we learned more about it, and now it's called 1I/2017 U1,

  • or just 'Oumuamua, a Hawaiian term roughly meaning something like

  • messenger from the distant past.”

  • But no translation, or pronunciation, is perfect, so please feel free to correct me.

  • Ever since it was first discovered, telescopes worldwide have frantically turned toward 'Oumuamua

  • to study it before it's too far from the Sun to see.

  • And scientists released their first results last week, in a paper published in the journal

  • Nature and another submitted for review in The Astrophysical Journal.

  • And TL;DR: 'Oumuamua is generally kind of boring, but in the best way.

  • Comets tend to be the fastest things in our solar system,

  • so they'd be mostly likely to get kicked into interstellar space.

  • But based on the light 'Oumuamua reflects and its lack of a tail,

  • scientists think it is much more like a rocky asteroid than an icy comet.

  • In fact, the reflected light makes it look a lot like our asteroids;

  • 'Oumuamua would fit right in with the hundreds of thousands of asteroids orbiting the Sun right now.

  • They're made of pretty much the same stuff.

  • Based on how the brightness of the reflected light changes over time,

  • scientists also think that 'Oumuamua is spinning around every seven hours or so.

  • And for something half a kilometer long to spin that fast,

  • it has to be made of some fairly strong rocks,

  • although that's pretty normal in our solar system's asteroids, too.

  • The most surprising characteristic of 'Oumuamua is probably its shape.

  • The light changes so dramatically as it spins that 'Oumuamua seems to be about

  • ten times longer than it is wide, so it's probably shaped like a cigar or a marker.

  • Some people online have started speculating

  • that 'Oumuamua is exactly the same shape and size as an alien spaceship.

  • And as soon as they provide their close-up, high-resolution, peer-reviewed pictures

  • of alien spacecraft, we can start comparing their shapes and characteristics.

  • But as far as any scientists can tell, this thing's just a normal asteroid.

  • Which is exactly why it's so exciting: it helps confirm that there's nothing special

  • about our neck of the galaxy.

  • If our solar system is normal, that means what happens here

  • probably happens all over the place.

  • So even though we can't visit other star systems,

  • we can learn more about them by studying our own.

  • Which brings us to the other weird asteroid that's about to pass by.

  • Among those hundreds of thousands of asteroids orbiting the Sun,

  • we only know of one that produces a meteor shower.

  • It's called 3200 Phaethon.

  • And around December 16, it'll be kind of near the Earth,

  • but not nearly as close as you'd think based on some recent articles.

  • Most meteor showers come from Earth plowing through the dusty debris

  • left behind comets that pass near our orbit.

  • When those dust grains burn up in our atmosphere, they produce bright streaks across the sky.

  • But in 1989, an astronomer noticed that the annual Geminid meteor shower,

  • which happens around the middle of December, doesn't follow this pattern.

  • Instead, it's from 3200 Phaethon, a five-kilometer-wide asteroid

  • that orbits the Sun about every year and a half.

  • Asteroids don't usually have dust trails that could cause something like a meteor shower,

  • and astronomers still aren't sure why Phaethon is the only known exception.

  • One popular explanation is that Phaethon used to be a comet,

  • but it ran out of loose dust sometime in the last couple thousand years.

  • And since then, it's just looked like any other asteroid.

  • We know that's a thing that can happen based on other dead comets we've seen,

  • and it makes sense: Phaethon's orbit is pretty small for a regular comet,

  • and it actually gets closer to the Sun than any other named asteroid.

  • It spends so much time being warmed and exposed to the particles and radiation pressure

  • coming from the Sun that it might have basically run out of dust.

  • This idea gained more support when sudden bursts of dust flew off Phaethon

  • as it got closer to the Sun in 2009 and 2012, just like they might fly off a rocky comet.

  • But not everyone agrees.

  • The grains in those recent bursts were way smaller than the ones in the Geminids,

  • which is one of the best annual meteor showers

  • because of the relatively large grains that produce it.

  • So other scientists think Phaethon used to be bigger but broke apart,

  • leaving behind the Geminids and a few asteroids.

  • But hardly any of that information made it into most of the Phaethon stories

  • that have been circulating recently.

  • They mostly focused on the fact that it'll be about

  • ten million kilometers from Earth on December 16.

  • That's about 25 times farther than the Moon is, with absolutely zero chance of hitting Earth,

  • or re-killing the dinosaurs, or whatever else a banner graphic might've suggested.

  • And just to cover all our bases: Phaethon is not an alien spaceship, either.

  • But the dust it's left near our orbit puts on a pretty good show.

  • The Geminids are best around December 13,

  • but they last for the first couple weeks of December.

  • You can see them from pretty much anywhere on Earth,

  • and they'll mostly seem like they come from the constellation Gemini,

  • right near Orion's Belt, but really, you can look anywhere in the sky.

  • With more than a hundred meteors an hour under the right conditions,

  • the Geminids are pretty hard to miss.

  • So if you can, you might want to spend some time

  • looking at the late night sky in the next few weeks.

  • You won't regret it.

  • ...Unless it's cloudy, in which case I'm really sorry.

  • Maybe pick a different night.

  • So, here's an Exciting Announcement!

  • It's that time of year where a lot of people buy each other gifts.

  • And that's not really the announcement I wanted to make,

  • but we made a thing that can help with that!

  • It's called SciShow Finds and it's a little portal to a select few artifacts of this universe

  • that we love and think are special and thought you would too.

  • This is Hank's newest brainchild

  • and he's meticulously curated thefindswe have there now.

  • I picked out the Mberry tablets which make everything you eat sweet.

  • You can eat a lemon or drink vinegar and they taste like candy,

  • and it's amazing and super weird!

  • We did a SciShow about them

  • and I just want everyone to get to experience those weird tastes.

  • But, you're watching SciShow Space, so you probably care most about my favorite finds

  • like this space shuttle lapel pin designed by SciShow pal Valerie Barr,

  • or these Olympus Mons socks designed by Bill Mead, who works on SciShow and SciShow Kids.

  • We're hoping to add a new finds as we find them throughout the year, so all of those

  • new ones will replace these ones, so all of these are only available for a limited time.

  • So if you're looking for the perfect stocking stuffer for someone,

  • or just something to treat yourself, SciShow Finds is a good spot to check out.

  • And know that when you shop at SciShow Finds, you're supporting SciShow

  • and everything we do, just like you are by watching right now.

  • So, Thank you.

  • [♪ OUTRO]

[♪ INTRO]

字幕と単語

動画の操作 ここで「動画」の調整と「字幕」の表示を設定することができます

B2 中上級

恒星間小惑星で初の結果が出た! (The First Results on the Interstellar Asteroid!)

  • 0 0
    林宜悉 に公開 2021 年 01 月 14 日
動画の中の単語