All the thin lines are caused by tiny amounts of complex elements 这些细细的线条，都是微量复杂元素造成的

metals like iron and magnesium.  好比说像铁或镁等金属

But there are 3 very deep,broad lines,  但是这里有三条很暗、很粗的线条

and they are all caused by  它们都是

an enormous amount of a single element.  由大量单一元素形成的

There's some helium and traces of heavier elements.  太阳中含有氦和少量较重的元素

But over 90% of the sun is Hydrogen.  但有90%是氢

It is the simplest and most common element in the universe.  氢是宇宙中最简单也最常见的元素

The secrets of the sun's power must lie in this gas.  太阳能量的秘密，想必和这种气体有关

Look carefully into the night sky  仔细观察夜空

and you'll see huge clouds of  你会发现大片由氢组成的云

hydrogen floating in interstellar space.  在星际间飘移

These are nebulae.  这些是星云

And they can be hundreds of light years across.  它们直径可能高达数百光年

They are some of the brightest areas in the sky  星云被新近形成的巨大恒星强光照亮

lit up by the intense light of newly formed massive stars.  是空中最明亮的区域

In them we can see stars being born.  我们可以在星云中看到诞生中的恒星

It is to areas like this that astronomers turn  天文学家用望远镜观察这些区域

their telescopes when they want to study how our sun was formed.  以研究太阳的形成过程

There she is,  在那里

okay,so now let's recentre on her.  把焦距移到这里

By studying different nebulae it's possible to  科学家藉由研究不同的星云

piece together the stages in which stars are made.  拼凑出恒星的形成阶段

And it all starts in a cold dark cloud,  这一切的起点，是一片冰冷、黝黑的云

floating around waiting for something to happen.  飘浮在虚无中等待大事发生

Cold clouds like this are actually quite stable.  像这样的冰冷云朵其实很稳定

They will sit there for a very very long time,  有时它们会静止很长很长时间

for thousands and in some cases millions of years  几千，甚至几百万年

before they'll actually do anything.  才会发生变化

What you need to do to get the star formation process going  它们要受到刺激

is you need to kick it with something.  才会展开恒星形成的过程

That can be the impact on the cloud  刺激可能来自

from one side by a supernova blast wave;  超新星的爆炸波

a massive star nearby has gone boom at the end of its life  邻近的巨大恒星在生命尽头爆炸

and that sends out in all directions very energetic  并朝四面八方发出能量十足的压缩波

compression waves that hit the gas and compress it.  压缩波撞击气体并将之压缩

The shock waves knock the cloud out of balance.  云朵因震波而失去平衡

Causing localised clumps of hydrogen to form.  并导致某些区域出现氢气团块

These are the seeds from which stars grow.  这就是萌生恒星的种子

The increased gravity of the seeds sucks in more  种子与日俱增的引力吸引越来越多氢气

and more hydrogen in a runaway process  这样的出走过程

that lasts for a million years.  会持续一百万年

As more hydrogen is squeezed into the clumps the temperature rises.  团块聚集的氢气越多，温度就越高

They are not yet producing light  它们还不会发光

but they are well on the way to becoming stars.  但已踏上成为恒星的道路