巨蟹星云的英文：
crab nebula

crab是什么意思：
n. 螃蟹，爱争吵的人，偏航
v. 捕蟹，偏航，发牢骚

Crabs harbor in holes.
蟹躲藏在洞里。

My neighbor is such an old crab.
我的邻居可真是个爱争吵的人。

A crab has two clams.
螃蟹有两个钳。

Crabs scuttle along the muddy bank.
几只螃蟹沿着泥泞的河堤快速横行。

You can not make a crab walk straight
不要强人所难

nebula是什么意思：
n. 星云,云翳

The spiral nebulae are impressive objects.
旋涡星云是迷人的天体。

The element hydrogen comprises 90% of the matter in gaseous nebulae
元素氢占气体星云物质的90%。

The element hydrogen comprises 90% of the matter in gaseous nebulae.
元素氢占气体星云物质的90%。

galactic nebulas are masses of diffuse material within our galaxy
银河星云是我们星系中的一团团弥散物。

Good spectra of the spiral nebulas are difficult to obtain because of their extreme faintness
旋涡星云因为非常暗，难以得到它们的清晰的光谱。