Gas Noted Wavelengths Radiation Change Flowed Galaxy Emit

意群训练： He noted that the wavelengths of the radiation emitted by a gas would change as the gas cooled ，so that as the gas flowed into the galaxy and became cooler ，it would emit not x-rays ，but visible light ，like that which was captured in the photographs .

标志： He noted that the wavelengths ［of the radiation (emitted by a gas)］would change /as the gas cooled/, so that /as the gas flowed into the galaxy and became cooler/, it would emit not x-rays, but visible light, like that which 　was captured in the photographs.

译文： 他 指出 ，［（一种气体发射出来的）辐射的］波长 /当这种气体冷却的时候/将会发生改变 ，以至于 /当气体流入星系并变得更冷的时候/，它 所发射出来的不是 X射线，而是 可见光，就好像被照片所捕捉下来的情形 那样。

解释： that引导的宾语从句比较长，但是结构还算简单，需要解释的是最后的“that which”，其实就等于what。不过阅读现场的这种替换比较耽误时间，读者在现场最快的反应，就是把它看成“具有后面的特征的东西”，英文相当于one that或者ones that。