When that happens, you get that idealized soap bubble nebula.

如此一来，就会得到理想肥皂泡云。

In a lot of nebulae there's no sharp edge; they just kinda fade away.

在很多云中并没有尖锐缘；它们只是会慢慢消失。

However, this nebula started off more or less as a big shapeless blob.

但是一开始这云或多或少更像个不成形水滴。

The orion nebula is a special kind of nebula called a stellar nursery.

猎户座云是一种云，叫做恒摇篮。

He saw clusters of stars, brightly colored nebulas, even entire galaxies!

他看到了无数团，明云，甚至还看到了整个银河！

But sometimes nebulae do have sharp edges.

但有时云确实有锋缘。

That's a very common shape for planetary nebulae.

这是行状云很常见形状。

It is a nebula: a star-forming region where new stars are being born.

一个正在诞生新恒恒形成区域。

Among the other four images were two that showed huge clouds of gas and dust – called nebulas.

在其他四张照片中，有两张展示了巨大气体和尘埃云——也就是云。

Orion's sword is home to the great orion nebula, a cloud of dust, hydrogen, helium, and other gases.

猎户剑位置有猎户座云，是一种由尘埃、氢气、氦气及其他气体组成云。

Those elements will spread out to become a nebula, a rich chemical cloud drifting through space.

这些物质最后会扩散开来，形成新云，即一大团富含化学物质云团飘逸在宇宙之中。

So planetary nebulae really may owe their existence to planets!

所以行状云存在可能真要归功于行！

That usually happens when a gas cloud is expanding, like in a planetary nebula or supernova.

这通常发生在气体云膨胀时，比如行状云或超新。

Gas inside a nebula can be in turmoil, too.

云内气体也可能处于混乱状态。

The Orion nebula is one of the wonders of the universe.

猎户座云是宇宙中奇迹之一。

These can create lovely sheets, tendrils, and filaments in nebulae as well.

这些也可以在云中创造出可爱片状、卷须和丝状物。

At the centre of the nebula lies the remnant of the star, its core, crushed by the force of gravity.

在云中心处，这颗恒核依然存在着，在引力作用下它已是面目全非。

Everything we find on the Earth today also originated in that nebula.

我们地球上一切也都来源于那片云。

The glow in a planetary nebula is due to the hot central white dwarf exciting the gas.

行状云中光芒是由中央炽热白矮激发气体产生。

Stars, nebulae, stellar clusters of various sorts, the occasional supernova.

恒、云、各种类型团，偶尔还有超新。