The structure of a star can often be thought of as a series of thin nested shells, somewhat like an onion.
恒星的结构经常被想象成一系列套在一起的薄层，就像洋葱一样。
2
The structure of an onion allows us to perform the skin-peeling exercise several times, progressing ever deeper into the onion’s inner secrets with every skin peeled off.
我们能够对一个洋葱图结构进行多次脱皮，不断将每层皮剥落，直到进入到洋葱的内心。
3
In structure it is somewhat like a transparent onion, formed of roughly 22,000 very fine layers.