The evolution of the intermediate-mass stars is a good example of the process by which stars are born, live, and die. This star begins as a swirling cloud of gas that takes 100,000 years to collapse into a protostar. Hydrogen fusion begins in the protostar and causes the creation of a T-Tauri star which is a variable brightness star. This new star contracts for 10 million years until the core energy is balanced with gravity. "The star has begun the longest part of its life as a producer of energy from hydrogen fusion, the main-sequence phase...The amount of time a star spends there depends on its mass" but is likely to be billions of years (Green, 2005, p. 6). When the balance between the production of fusion energy and gravity shifts, compression occurs and the star enters the "red giant" phase where it expands greatly and appears red in color....
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