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  • One day, the last star will die, and the universe will turn dark forever.

    ある日 最後の星が死に

  • It will probably be a red dwarf, a tiny kind of star,

    宇宙は闇に包まれる

  • that's also one of our best bets to find alien life,

    その星はおそらく赤色矮星で

  • and might be the last home of Humanity before the universe becomes uninhabitable,

    その特徴から言って

  • so what do we know about them, and why are they our last hope?

    人類の最後の住処となる場所だ

  • At least 70% of stars in the universe are red dwarfs.

    なぜこの星が人類最後の希望なのか

  • They are the tiniest stars out there, with only about 7 to 50% of the mass of our sun,

    宇宙にある恒星の70%は赤色矮星だ

  • not that much bigger than our planet, Juptier, which is still huge, though.

    小さな星であり

  • They are also very dim.

    質量は太陽の7~50%ほど

  • It's impossible to see them with the naked eye.

    木星よりは大きい

  • You've never seen one in the night sky.

    大きいが とても暗い

  • Even with all our technology,

    夜空に肉眼で見ることはできない

  • we can only clearly observe red dwarfs in our neighborhood.

    現代技術なら近くのものが観測でき

  • Approximately 20 of the 30 stars close to Earth are red dwarfs.

    20個ほどが見つかっている

  • Like all stars, red dwarfs fuse hydrogen into helium,

    赤色矮星も他の星同様 核融合を行う

  • but while more massive stars accumulate all the fused helium in their cores,

    大きな星は核で核融合を行うが

  • red dwarfs stay convective, meaning that the helium and hydrogen constantly mix,

    赤色矮星は流動的で

  • so they use up their fuel incredibly slowly before they are extinguished.

    中が混じり合っている

  • Red dwarfs burn so slowly

    そして燃料の消費速度がとても遅い

  • that their average lifespan is between one and ten trillion years;

    ゆっくり燃えるため

  • by comparison, the Sun will survive for another five billion years.

    平均寿命は1~10兆年まで及んでいる

  • Because the universe is only 13.75 billion years old,

    太陽の寿命は残り50億年だ

  • not a single red dwarf has reached later development stages.

    宇宙の年齢は137億年だから

  • Every single one of the trillions that exist is still a baby.

    死んだ赤色矮星はいない

  • Speaking of babies, the smallest star in the entire universe

    赤色矮星はみんなまだ赤ちゃんだ

  • is also a red dwarf because small red dwarfs are right on the verge of being a star at all.

    また宇宙で最も小さな恒星でもある

  • Just a tiny bit less hydrogen, and they are mere brown dwarfs,

    恒星になれる最小の大きさだからだ

  • failed stars that cannot sustain a fusion reaction for long,

    これ以下だと褐色矮星になる

  • so what about aliens or a new home for Humanity?

    核融合できないただの星だ

  • Since our sun will die one day, we'll eventually need to look for a new home,

    生物にとってはどんな場所だろうか

  • and where there are habitable planets, there might also be aliens.

    太陽が死んだら 新しい家が必要だ

  • The Kepler space observatory found that at least half of all red dwarfs host

    快適な場所なら 宇宙人がいるかも

  • rock planets between half and four times the mass of our Earth.

    観測では 赤色矮星の半数に

  • Many of them are in the habitable zone, the area around a star where water can be liquid,

    地球の半分以下の小さい惑星がある

  • but since red dwarfs burn at relatively cold temperatures,

    水が液体で存在できる

  • a planet would need to be really close to be hospitable,

    良い距離のものもある

  • probably as close as Mercury to our Sun or even closer

    赤色矮星は温度が低いため

  • which brings with it all kinds of problems.

    その距離は短くなる

  • For example, a planet this close to a star would probably be tidally locked,

    太陽と水星の距離くらいだろう

  • meaning the same side would always face it.

    だがこれが問題をもたらす

  • This side would be incredibly hot, while the shadow side would be frozen

    近すぎるために向きが固定され

  • which makes it hard for life to develop;

    常に同じ面が向く

  • although, a planet with a big enough ocean might be able to distribute the star's energy

    表はとても熱く

  • and create some kind of stability.

    裏は凍りついて住みにくいだろう

  • All the gravitational forces of the red dwarf could squeeze the planet

    惑星に大きな海があれば

  • and heat it up so much that it might lose all its water over time.

    熱が分散されて安定するが

  • These planets could end up like Venus, a hot burning hell.

    強い重力によって惑星は角張り

  • Another problem is that many red dwarfs vary in their energy output.

    水も蒸発してなくなるかもしれない

  • They can be covered in star spots that condemn their emitted light by up to 40% for months

    そして金星のような灼熱地獄になる

  • which would cause oceans on planets to freeze over;

    出るエネルギーの安定性も問題だ

  • at other times, they can emit powerful solar flares,

    黒点が現れ 光を40%に弱め続ければ

  • sudden outbursts of energy incredibly powerful.

    惑星の海は凍ってしまう

  • These red dwarfs could double their brightness in minutes

    また時には強力なフレアが

  • which could strip away sizable portions of a planet's atmosphere and burn it,

    突然火を噴くこともある

  • rendering it sterile;

    数分で倍の明るさになり

  • on the other hand, their extremely long life span is a big plus.

    惑星の大気の大部分を

  • A red dwarf with just moderate levels of activity

    燃やし尽くしてしまう

  • could be an amazing place for a planet that hosts life.

    それでも寿命の長さは利点だ

  • Life on Earth has existed for about four billion years,

    活動が安定していれば

  • and we have about a billion years left before the Sun becomes so hot

    移り住むにはとても良い

  • that complex life on Earth will become impossible.

    生命は40億年存在してきた

  • We will either die out or leave Earth and look for a new home.

    だが太陽は10億年後には

  • We could build a civilization for potentially trillions of years

    熱くなりすぎている

  • around a red dwarf with the right conditions.

    そうなる前に引っ越しが必要だ

  • About 5% of the red dwarfs in the Milky Way may host habitable, roughly Earth-sized planets.

    良い条件の星があれば

  • That would be more than four billion in total,

    数兆年住むことができる

  • but life may not even need a planet like Earth.

    赤色矮星の5%には

  • Candidates for life around a red dwarf may be the moons of gas giants,

    地球に似た惑星が存在し

  • also called Super Earths, really massive rocky planets.

    全部で40億個ある

  • All alone, there are an estimated 60 billion potentially habitable planets

    地球に似てはいなくても

  • around red dwarfs, and that's in the Milky Way alone,

    巨大ガス惑星の衛星や

  • so red dwarfs might become really important for our survival in the future,

    巨大な岩 スーパーアースがある

  • but everything has to die at some point, even red dwarfs.

    これらの星が600億個

  • When in trillions of years the life of the last red dwarf in the universe is about to end,

    赤色矮星の周りに存在する

  • it will not be a very spectacular event.

    この天の川銀河だけで

  • As its hydrogen runs out, it shrinks becoming a blue dwarf, burning out completely.

    赤色矮星は将来 重要になるだろう

  • After its fuel is spent, it's transformed into a white dwarf,

    しかし赤色矮星もいつかは死ぬ

  • an object about as small as Earth, packed very densely,

    数兆年後 赤色矮星が死ぬ時が来るが

  • and made of degenerate gasses, mostly of Helium-4 nuclei.

    特に大したことは起きない

  • Having no more source of energy, it will cool extremely slowly

    縮んで青色矮星になり さらに燃える

  • over trillions of years until it becomes its final form: a cold black dwarf.

    燃え尽きると白色矮星になる

  • White and black dwarfs are so fascinating that they deserve their own video;

    地球大で密度が高く

  • anyway, it's going to be a long time before the last stars in the universe vanish.

    ほとんどヘリウム4でできた物体だ

  • It's kind of uplifting to know that, if Humanity succeeds in venturing into Space,

    もうエネルギー源はなく

  • we have plenty of time before the universe turns out the lights.

    数兆年かけて冷えて

  • Our videos are made thanks to your support on Patreon.com.

    最後の形 黒色矮星になる

  • If you want to help us make more of them, we really appreciate your support!

    これらは別の動画で説明しよう

  • Subtitles by the Amara.org community

    最後の星が死ぬまで長い時間がある

One day, the last star will die, and the universe will turn dark forever.

ある日 最後の星が死に

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B2 中上級 日本語 惑星 宇宙 恒星 太陽 融合 寿命

宇宙最後の星-赤い小人の説明 (The Last Star in the Universe – Red Dwarfs Explained)

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    簡簡哲 に公開 2021 年 01 月 14 日
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