translation.en: Astronomers now believe that every star in the galaxy has a planet, and they speculate that up to one fifth of them have an Earth-like planet that might be able to harbor life, but we haven't seen any of them.
translation.zh: 宇航员现在相信银河系的每个星球 都有一个行星， 并且他们推测他们中间的五分之一 有着一个类似地球的行星 可能会存在生命， 但是我们还没有看见他们中的任何一个