Newly Discovered Star Type

While I’ve come to be rather accepting of the fact that astronomers and astrophysicists probably know what they are doing, I still find it hard to understand how they can determine that a dim little white dwarf star, some 800 light years away, is made mostly of pulsating, super hot carbon.  Okay, I know it has something to do with light spectrum and red/blue shifts but all and all I have a hard time wrapping my head around it.  Anyway, feel free to read about this new star in Discovery News.