For 100 years astronomers have paid particular attention to a class of variable star known as the Cepheids.
过去100年来，天文学家特别注意一类称作“仙王座变光星”的恒星。
And, since individual Cepheids are bright enough to be seen in other galaxies, they were the first tool used to estimate the distances to such galaxies.
且由于在另一个星系中的单颗“造父变星”的亮度就足于使其被观测到，所以它们是测算类似星系距离的首选工具。
Cepheids are a special type of star that pulsates in a predictable way, and like the type 1a supernova, they are assumed to be the same, no matter where they are located.
造父是种特殊的恒星，它能以可以预测的方式周期脉动，就像I型超新星，他们被当做是一样的，不管他们在那里。
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