北极星似乎由一颗脉动的恒星衍变而来。
The Pole Star appears to be changing from a star that pulsates.
这个过程可能周而复始，周期性地重复--天文学家称之为"脉动"对不稳定性超新星--直至恒星失去足够的物质，在普通超新星的形态中走到生命的尽头。
The cycle can repeat itself in pulses—astronomers call this case a “pulsational” pair-instability supernova—until the star loses enough mass to end its life in an ordinary supernova.
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。
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.
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