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"collapsing star" refers to a celestial object, like a star, that is undergoing a process of collapsing or shrinking in on itself. It usually happens when the star runs out of fuel and its core can no longer sustain the nuclear reactions that were responsible for keeping it stable and shining bright. The star's own gravity then causes it to collapse inward, leading to intense pressure and temperature changes, and potentially resulting in a powerful explosion or the formation of a very dense object, like a black hole or a neutron star.
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