• The high mass stars (M > 5 Msun) then follow an evolutionary sequence that burns progressively heavier elements up to Fe:

      • He Right Arrow C & O.
      • C & O Right Arrow Ne.
      • Ne Right Arrow Si.
      • Si Right Arrow Fe.

    • Iron (Fe) is a unique nucleus in that you cannot get energy out of it from either fusing it or breaking it apart (i.e., fission). Once an Fe core forms, no further nuclear reactions can occur to halt its collapse.

      • The collapsing core reaches nuclear densities and bounces, producing a supernova explosion that blows apart the outer 9/10th of the star, meanwhile the core becomes a neutron star.

      • The most massive stars have cores that collapse down to a black hole!

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