High-mass stars containing more than eight solar masses have a very different evolution from low mass stars and have an explosive death that is responsible for forming many of the heavier elements in the universe.
Evolved high-mass stars have a core with concentric zones of progressively heavier fuel, with the burnt "ash" of one layer forming the fuel for the next deeper layer in the star. At the edge of the core, hydrogen burns to fuse helium, then helium burns to fuse into carbon, which fuses into oxygen. The oxy gen goes through nuclear fusion to form neon, which then forms magnesium, then silicon, and then iron nuclei ash in the core of the massive star. As each fuel is used up, the core of the star contracts, heats up, then starts to burn the fuel of the ash of the previous episode of burning. Each successive burning stage is hotter, proceeds faster than the one before, and lasts for a much shorter time. A typical massive star that is about 20 solar masses may burn hydrogen for 10 million years, helium for 1 million years, carbon 1,000 years, oxygen for 1 year, silicon for a week, and iron for less than one day. After this the core of the massive star collapses, and one of the universe's most spectacular events unfolds.
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