The lifecycle of a massive star, which typically refers to stars with a mass greater than about eight times that of the Sun, involves several key stages. Here is a possible sequence in the lifecycle of a massive star:
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Stellar Formation: A massive star begins its life in a molecular cloud, where gravitational instabilities cause gas and dust to collapse, forming a protostar.
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Main Sequence: Once nuclear fusion begins in the core, converting hydrogen into helium, the star enters the main sequence phase. Massive stars have high temperatures and pressures at their cores, leading to rapid fusion.
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Hydrogen Burning: During this phase, the star remains in hydrostatic equilibrium as it steadily fuses hydrogen into helium in its core.
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Red Supergiant Phase: As hydrogen in the core is exhausted, the star's core contracts and heats up, while the outer layers expand and cool, turning the star into a red supergiant.
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Helium Burning: When the temperature in the core becomes sufficient to ignite helium fusion, the star begins to fuse helium into heavier elements such as carbon and oxygen.
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Advanced Burning Stages: Depending on the mass of the star, further fusion processes occur, creating heavier elements through successive stages: carbon burning, neon burning, and so on, ultimately reaching iron.
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Supernova Explosion: Once the core becomes primarily iron, fusion can no longer release energy. The core collapses under gravity, leading to a catastrophic explosion—the supernova. This explosion can outshine entire galaxies and disperses elements into space.
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Remnants: The remnants of the massive star can either become a neutron star or a black hole, depending on the core's mass after the supernova.
This lifecycle illustrates the progression from stellar birth to the explosive end of a massive star and the formation of compact remnants that can continue to influence their surroundings and contribute to the ongoing cycle of stellar evolution.