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HR-diagram: Describing the sun's life cycle

  1. Apr 9, 2016 #1
    We are asked to describe the sun's life in 4 different sequences of the HR-diagram. The second one is in main sequence, third one is in the red giant area, and the last one is in the white dwarf area. The first one is the one I cannot understand. I recreated where the numbers are on a new HR-diagram: http://i.imgur.com/H3nqvQA.jpg?1

    I know that all stars that have just been born/can be defined as a star, will come to the main sequence. Since they're using hydrogen as a fuel. I also know that a brown dwarf would be far down outside the diagram, and I would assume that the sun was more like a brown dwarf before it eventually became a star. So I don't understand why there is on just ''out there''.. Maybe it's a trick question? My teacher has not asked any trick questions before so I find it a little strange.. I would very much appreciate it if anyone could help me understand!:smile:
  2. jcsd
  3. Apr 9, 2016 #2


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    A brown dwarf never achieves sufficient mass to sustain hydrogen fusion in its core.

    OTOH, a star like the sun takes a while to accumulate enough mass to begin fusion reactions in its core. Presumably, this mass accumulation phase is what's occurring during 1-2 on your HR diagram.
  4. Apr 9, 2016 #3
    Okay, thank you! :)
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