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ExploraTour: A Peek into the Lives of the Stars

What Happens to High Mass Stars (>8 Solar Masses)?

STAGE 2: Red Supergiant Phase

After the star depletes the hydrogen in its core and moves off the main sequence, the core contracts and heats causing the outer layers to expand. The expansion of the outer layers results in a cooling of the surface temperature. The star gets redder but stays about the same brightness. This happens because it is increasing rapidly in size. It first becomes a blue supergiant (like Rigel) and then cools and expands to a white supergiant (like Deneb).

Meanwhile the core is getting hotter reaching 150 million K. At this temperature, helium (He) fuses explosively into carbon (C) and oxygen (O). For lower mass stars, nuclear reactions at this stage cease and the star collapses to a white dwarf. But red supergiants are much more massive.

Gravitational collapse continues to raise the temperature of the core. When the core reaches an amazing 1 billion K, carbon fuses to produce nitrogen (N), magnesium (Mg) and oxgyen (O). These elements fuse to produce even heavier elements.

At each stage less total energy is released and thus the stages get progressively more short-lived. Finally an iron core is produced. Since no energy can be gained by fusing iron to make higher mass elements, the core collapses at blinding speeds.

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ExploraTour - Looking at the World in a Different Light

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ExploraTour - Looking at the World in a Different Light

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ExploraTour - Looking at the World in a Different Light

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ExploraTour - Looking at the World in a Different Light

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ExploraTour - Looking at the World in a Different Light

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA