Placeholder Image

字幕表 動画を再生する

  • Shira Polan: In 2015, astronomers

  • noticed something strange

  • going on nearly 1,500 light-years from home.

  • A star named KIC 8462852,

  • aka Tabby's Star, kept dimming,

  • as though something was passing in front of it.

  • Since then, scientists have been trying to figure out

  • what that something might be.

  • A swarm of comets flying by en masse?

  • An alien megastructure?

  • Then, in 2019, astronomers proposed a new,

  • more plausible explanation

  • that might finally solve the mystery of Tabby's Star.

  • There are really two

  • mysteries centered on Tabby's Star.

  • First, the star keeps brightening and dimming

  • in a bizarrely sporadic pattern.

  • While very young stars occasionally do this,

  • astronomers have never seen this behavior

  • in a star of Tabby's age.

  • Second, the star is slowly

  • but surely getting dimmer over time,

  • in a steady decline that astronomers

  • have never observed

  • in another star of its type.

  • Clearly, something fishy is going on.

  • Some researchers have suggested

  • an advanced alien civilization is to blame.

  • If aliens built a megastructure

  • called a Dyson Sphere to siphon off the star's energy,

  • that could explain how the star

  • is a whopping 10% dimmer

  • than it was just a century ago.

  • But there are some holes in that idea.

  • For one, you'd expect an orbiting megastructure

  • to make regular, predictable trips around the star,

  • just like the International Space Station

  • makes regular trips around the Earth.

  • But, so far, there is no clear evidence

  • that the dips occur on a consistent schedule.

  • Plus, when it comes to any theory

  • about advanced alien civilizations...

  • Brian Metzger: It's a little hard to test it.

  • Polan: That's Brian Metzger, an astrophysicist

  • at Columbia University.

  • He studies what he calls...

  • Metzger: Things that go bump in the night.

  • Polan: Or strange phenomena in the universe,

  • including the odd behavior of Tabby's Star.

  • Metzger says another theory has problems as well.

  • You see, some experts suggest a massive swarm

  • of comets is the real culprit.

  • This has the advantage that, unlike aliens,

  • we're positive comets exist.

  • And if they were orbiting the star,

  • they'd explain the random blips, but...

  • Metzger: A lot of the explanations

  • run into the problem of:

  • Why is this relatively rare?

  • Like, why don't other stars show this behavior?

  • Polan: Basically, there would need to be something special

  • about Tabby's Star to attract so many comets

  • to congregate at the same time at the same place.

  • But as far as astronomers can tell,

  • Tabby's Star is just like any other star of its type.

  • Luckily, Metzger and his team may have a new solution.

  • In 2019, they published a paper

  • in the Monthly Notices of the Royal Astronomical Society

  • that argued for a different culprit:

  • the dusty remains of a dying moon.

  • According to Metzger's models,

  • a gas giant may have

  • orbited the star millions of years ago.

  • And, like Jupiter and other gas giants,

  • it hosted a few icy moons.

  • Now, the planet and its

  • moons would have continued

  • to orbit Tabby's Star to this day,

  • if not for one problem.

  • Metzger says a second nearby star

  • may have exerted

  • a tiny gravitational pull on the planet.

  • Over time, it slowly tugged the planet

  • out of its orbit and towards Tabby's Star

  • until, eventually, the planet fell in

  • and was destroyed.

  • But the planet's moons may have escaped this fate,

  • instead getting trapped into orbit by Tabby's gravity.

  • Over time, the constant radiation

  • could have melted off chunks of these icy moons,

  • resulting in a colossal cloud of moon dust around the star.

  • Now, this plan makes sense for a number of reasons.

  • First:

  • Metzger: Dust or small particulate grains

  • is a really effective way

  • to block the light of a star.

  • Polan: Unlike an alien superstructure,

  • dust floats around in a blob

  • that's constantly morphing and changing its shape,

  • which could explain the irregular dips.

  • And if enough of it accumulated around the star,

  • over time, it could lead

  • to that mysterious 10% dimming

  • astronomers observe.

  • The moon part of Metzger's hypothesis works well, too.

  • Metzger: So, you need an object which is

  • very massive

  • and has a lot of dust or has a lot of materials

  • that it could survive for a very long time,

  • that it could feed this giant cloud of debris.

  • Polan: Meanwhile, you'd need

  • a remarkably large swarm

  • of unusually giant comets

  • in order to get the same job done.

  • Metzger: We would need something much bigger

  • than an ordinary comet to explain

  • the dipping around Tabby's Star.

  • Polan: Plus, unlike an alien machine,

  • we see moons all the time.

  • And while we haven't seen this exact scenario before,

  • it's based on something we have observed

  • with Jupiter-like planets.

  • Metzger: So, we have lots of evidence

  • from other planetary systems

  • that the Jupiters can be driven into their stars.

  • Polan: And...

  • Metzger: If you think Jupiters are being driven

  • close to their stars, you have to say,

  • "What happened to their moons?"

  • Polan: So, mystery solved?

  • Not quite.

  • While Metzger says he's happy

  • with his team's explanation,

  • he still has plenty of work ahead of him.

  • Metzger: You know, I think it's important to, you know,

  • moving beyond what we're working on now.

  • The next thing is obviously to make some predictions

  • that can be tested.

  • Polan: After all, theoretical models only get you so far.

  • That being said, it's still probably not aliens.

Shira Polan: In 2015, astronomers

字幕と単語

ワンタップで英和辞典検索 単語をクリックすると、意味が表示されます

B1 中級

Astronomers Have Their Best Solution Yet To The Mysterious 'Alien Megastructure' Star

  • 4 0
    林宜悉 に公開 2020 年 10 月 24 日
動画の中の単語