The stars are known as Cepheid variables.

这些恒星就是我们熟知的造变星。

The system belongs to a kind of binary star known as cataclysmic variable.

该系统属于一种被称为激变变星的双星。

And... And right in the middle, there's a variable star that I discovered.

而… … 而在正中央有一颗我所发现的变星。

In 1925, when Edwin Hubble looked at the brightness of variable stars in a smudge called Andromeda, they appeared much dimmer than their pulsing rate predicted, and Hubble realized these stars were too far away to be in the MilkyWay.

1925 当 Edwin Hubble 看着仙女座星体中各种变星的亮度，发现它们的亮度比预测的要暗的多，并且 Hubble 也认识到这些恒星在一个很远的地方，不可能是在银河系内。

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。

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，有一种名叫造变星（以仙王星座命名，第一颗造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”。

Skowron explained that Cepheids are giant stars that are far brighter than the sun.

斯考伦解释说，造变星是比太阳明亮得多的超巨星。

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

They observed variable stars in the Andromeda Galaxy that allowed them to get the distance to the galaxy.

他们观测了仙女座星系中的变星，这使得他们能够到达星系的距离。

Only 12 or so have orbital periods below 75 minutes.

只有12种左右的激变变星拥有低于75分钟的轨道周期。

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。

There are more than a thousand known cataclysmic variables.

已知的激变变星超过一千种。

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变星的实际距离，这就给我们造出一把宇宙测量尺。

While studying what we now call the Andromeda  galaxy in 1923, Hubble realised that one of the stars he was looking at was a Cepheid variable  star – a type of star that blinks brighter and dimmer over the course of weeks.

1923 ，在研究我们现在所说的仙女座星系时，哈勃意识到他所看到的其中一颗恒星是造变星——一种在几周内闪烁得更亮和更暗的恒星。

For example, Cepheids, when we go and try and discover them, like we did with Hubble, maybe one in a thousand stars that we measure turns out to be a Cepheid.

例如，当我们像哈勃那样去寻找造变星时，可能在我们测量的每一千颗恒星中，只有一颗是造变星。

Hertzsprung used these values to calibrate a scale, which allowed him to calculate the distance to the SMC and the intrinsic brightness of each of Leavitt's Cepheids in the SMC.

赫兹普朗利用这些数值校准了一个标尺，这使他能够计算出小麦哲伦云的距离， 以及莱维特在小麦哲伦云中每一颗造变星的内在亮度。

'I am preparing a work on variable stars. There is one of these which I have exceptionally observed for several months, and on this my great theory is mainly based.

“我正在准备一部关于变星的作品。其中之一是我几个月来特别观察到的，我的伟大理论主要基于此。

Actual variable stars do exist, but Tabby's Star doesn't fit that profile, it's what's known as an F-type main-sequence star, and shouldn't behave anything like this.

实际的变星确实存在， 但 Tabby's Star 不符合这种情况，它是所谓的 F 型主序星， 不应该有这样的行为。

However, before making calculations, the period-luminosity relationship has to be calibrated with nearby Cepheid variables, whose distance can be measured using the parallax method.

然而， 在进行计算之前，必须用附近的造变星来校准周期-光度关系，可以使用视差法测量其距离。

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

如果两颗造变星以相同的速率脉动，而其中一颗较暗， 那就意味着它实际上更远。