The stars are known as Cepheid variables.

这些恒星就是我们熟知的造父变星。

And since there were pulsating Cepheid stars whose actual distances we already knew, this let us build a cosmic measuring stick.

既然我们已经知道这些有规律脉动的造父变星的实际距离，这就给我们造出一把宇宙测量尺。

Now if two Cepheid stars are pulsating at the same rate, and one's dimmer than the other, that means one is actually farther away.

如果两个造父变星以相同的速率脉动，并且其中一个比另一个更加暗淡，这就意味着更暗的那个更远。

If two Cepheid stars are pulsating at the same rate, and one's dimmer than the other, that means one is actually farther away.

如果两颗造父变星以相同的速率脉动，并且一颗比另一颗暗， 这意味着一颗实际上距离更远。

In the early 1900s, astronomer Henrietta Swan Leavitt realized a class of stars called Cepheids pulsate, bright and dim, and every Cepheid that pulsates at the same rate has the same brightness.

1900 年代早期，天文学家 Henrietta Swan Leavitt 发现一系列名为造父变星，它们有规律地变亮和变暗，并且每个造父变星以相同的速率脉动就会有着相同的亮度。

She noticed that a type of star known as a Cepheid variable (after the constellation Cepheus, where it first was identified) pulsated with a regular rhythm-a kind of stellar heartbeat.

她注意到，有一种名叫造父变星（以仙王星座命名，第一颗造父变星就是在那里发现的）的恒星在有节奏地搏动——一种星体的“心跳”。

These are called Cepheid variables, and they were critically important, because it was known that the time it took them to pulse was directly related to their luminosity, how much energy they emitted.

这些被称为造父变星，它们非常重要，因为我们知道它们产生脉冲的时间与它们的光度直接相关，也就是它们释放的能量。