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Why does fusion stop once a massive star builds an iron core?

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  1. The star runs out of helium
  2. Fusing iron absorbs energy
  3. Iron is too light to fuse

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References

  1. Astronomy 2e, 23.2 Evolution of Massive Stars: An Explosive Finish openstax.org/books/astronomy-2e/pages/23-2-evolution-of-massive-stars-an-explosive-finish Checked 2026-10-10.
  2. NASA Science, Stars in an Exoplanet World science.nasa.gov/exoplanets/stars Checked 2026-10-10.

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