The life cycle of a star involves several stages, which depend largely on the mass of the star. Here is a detailed explanation using the terms provided:
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Nebula: The life of a star begins in a nebula, which is a large cloud of gas and dust in space. Under the influence of gravity, parts of the nebula begin to collapse and condense, forming a protostar.
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Main Sequence: As the protostar continues to contract, it heats up and eventually reaches a temperature where nuclear fusion can occur in its core. This marks the beginning of the main sequence stage, where the star spends the majority of its life, fusing hydrogen into helium. Our Sun is currently in this stage.
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Red Giants: Once a star exhausts the hydrogen in its core, it will begin to fuse helium and other heavier elements in a series of stages. For stars like our Sun, this expansion turns them into red giants. During this phase, the outer layers of the star are expelled, and the core becomes increasingly dense.
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Super Giants: For massive stars, after the red giant phase, they can become super giants as they continue to fuse heavier elements. This leads to an even larger expansion.
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Supernova: When a supergiant has fused heavier elements up to iron, it can no longer maintain the fusion process. The core collapses under gravity, leading to a dramatic explosion known as a supernova. This explosion disperses the outer layers of the star into space and can create new elements.
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White Dwarf: In the case of medium-mass stars (like the Sun), after the red giant phase and the outer layers have been shed, the remaining core becomes a white dwarf. This is a hot, dense remnant that will cool over time but will no longer undergo nuclear fusion.
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Black Hole: For massive stars that experience a supernova, if the remnant core is sufficiently massive (more than about three solar masses), it can collapse further into a black hole, an object with a gravitational field so strong that not even light can escape from it.
In summary, the life cycle of a star can be visualized as: Nebula → Main Sequence → Red Giants → (for massive stars) Super Giants → Supernova → (for lower mass stars) White Dwarf or (for high mass stars) Black Hole.