Name: 恒星間小惑星で初の結果が出た! (The First Results on the Interstellar Asteroid!)
Uploaded: 2021-01-14T10:31:19.000Z
Duration: 6 min 23 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

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

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

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

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

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.

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.

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

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,

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

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

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

字幕リスト動画再生

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

weird

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