the star around which the earth orbits. • any similar star in the universe, with or without planets.

The sun is the central body of the solar system. It provides the light and energy that sustains life on earth, and its position relative to the earth's axis determines the terrestrial seasons. The sun is a star of a type known as a G2 dwarf, a sphere of hydrogen and helium 870,000 miles (1.4 million km) in diameter that obtains its energy from nuclear fusion reactions in its interior, where the temperature is about 15 million °C. The surface is a little under 6,000°C.

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