The birth of a star:
Stars form out of clouds of dust and gas. The particles in the clouds gather together under their own gravity. The clouds merge and become more and more concentrated to form a Protostar.
As a Protostar becomes denser, it gets hotter. If it becomes hot enough, the nuclei of Hydrogen atoms and other light elements fuse together. Energy is released in the process, so the core gets hotter and brighter and stars to shine. A star is born!
Shining Stars:
Stars like the Sun radiate energy because of Hydrogen fusion in the core. This is the main stage in the life of a Star. It can continue for billions of years until the star runs out of hydrogen nuclei to fuse together.
- Energy released in the core keeps the core hot so the process of fusion continues. Radiation flows out steadily from the core in all the directions
- The force of gravity that makes a star contract is balanced by the outward pressure of radiation from its core. These forces stay in balance until most of the Hydrogen nuclei in the core have been fused together.
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