Then they start spewing dust and gases, forming a giant glowing head.

然后它们开始喷出灰尘和气体， 形成一个巨大的发光头。

When they get near the Sun the ice turns into gas, forming the long tail, and also releases dust that forms a different tail.

当它们靠近太阳时，冰变成了气体，形成了长长的彗尾，同时其释放出的尘埃又形成了另一个彗尾。

You can even see how the collision has shaped the gas, forming a bow shock in one cluster like the waves of water created by a rapidly moving boat.

你甚至可以看到碰撞是如何形成气体的，在一个星团中形成弓形冲击，就像快速移动的船只所产生的水波。

There are three main parts of a comet: the nucleus, or solid central structure made of rock, dust, and ice; the coma, or dust and gas forming a thin atmosphere around the nucleus; and the tails.

彗核，即由岩石、尘埃和冰构成的中心固体结构，彗发，即由尘埃和气体在彗核周围形成的稀薄气体，还有彗尾。