Most of them are small potato shaped pieces of ice and rock.

その大半は氷と岩でできており

Some are so far away from Neptune that they need 29 years to circle Neptune once.

海王星から遠く離れ

Almost all of them are asteroids trapped by Neptune's gravity.

29年かけて一周しているものもある

99.5% of all the mass around Neptune is concentrated in Triton.

そのほとんどが 昔は小惑星だった

It's the 7th biggest moon, and more massive than all other known moons

全体の質量の99.5％は

in the solar system that are smaller than itself combined.

トリトンが担っている

Its surface area is about as big as the mainland of Russia and Australia together.

太陽系で７番目に大きな衛星で

Also, Triton is one of only four objects in the solar system that we know is geologically active.

これ以下には小さい衛星しかない

Triton orbits Neptune in the 'wrong' direction, against the rotation of Neptune,

表面積はロシアと

which is unique in our solar system for an object as big as Triton.

オーストラリアを足したぐらい

We can conclude from this that Triton hasn't always been a moon of Neptune,

太陽系で地質的活動のある

but probably was a dwarf planet that was forced into submission by Neptune,

４つの星の一つだ

when the solar system was younger and more chaotic.

トリトンは海王星の公転と

The most popular theory here is that Triton was once part of a double system,

逆に周っており

when Neptune migrated to the outer edges of the solar system,

この大きさでは他にない特徴だ

its gravity interfered with the double system and catapulted the other object into space,

ここから トリトンは元々は準惑星で

while Triton was forced into orbit.

まだ太陽系が若かった頃に

This would of disrupted the orbits of other Neptune moons rather violently

海王星に捕まったと考えられる

and would most likely have either pushed them away from Neptune,

トリトンは二重惑星だったようで

or let them collide or crash into Neptune.

そこに海王星が近づいた時

This would explain why Neptune's moons are so dominated by Triton.

その重力の影響を受け

But, this will end one day,

片方は宇宙へ飛び去り

Triton is being slowed down by Neptune,

トリトンは衛星になった

and eventually,

これが元あった衛星に影響を及ぼし

it will either crash into it,

宇宙へ吹き飛ばされるか

or be ground by Neptune's gravity into a huge ring system, similar to Saturn's.

粉々に破壊されるかした

So, don't by real estate on Triton.

これがトリトンだけが大きい理由だ

Fixed English Subtiles by Mads Hagemann Nielsen - 2015

が それもいつか終わる

Subtitles by the Amara.org community

トリトンは減速し続けており