Stars shine because high temperatures and intense pressure at the core induces nuclear fusion, which releases energy in the form of light. Nuclear fusion happens when two atoms fuse together and create a new atom.Continue Reading
Inside a star, nuclear fusion causes hydrogen atoms to fuse into helium atoms. This fusion causes the release of gamma ray photons inside a star that travel outward against the star's gravity. Gamma rays, however, are not released immediately. Rather, they fight to escape from a star's core while repeatedly undergoing absorption and emission by atoms through nuclear fusion. This process happens so continuously that it might take 100,000 years for a photon to reach the star's surface.
When gamma ray photons manage to escape a star's core and have lost some of their original energy, they become visible light photons. Light photons travel outward from a star in a straight line until they encounter an object. Some light photons may travel forever if they never reach an object. However, when light photons reach eyes, the result is a person seeing the shining star.
When people see a shining star, the light often travels for many years before reaching their eyes. Light from the star, Sirius, for example, takes eight years to reach Earth.Learn more about Constellations