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Black holes can be defined as the set of events from which it is not possible to escape to a large distance. To understand how a black hole might be formed, one first needs to have an understanding of the life cycle of a star. A star is formed when a large amount of gas, mostly hydrogen, starts to collapse in on itself due to its gravitational attraction. As it contracts, the atoms of the gas collide with each other more and more frequently, and at greater and greater speeds.
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