The Sun is the nearest star to Earth. The Sun is about 150 million km from Earth. The diameter is more than 100 times greater than Earth's diameter. The Sun's mass is more than 300,000 times greater than the Earth's mass.
Nuclei of atoms combine in the Sun and release huge amounts of energy. This process is called nuclear fusion. The temperature at the core is more than 15,000,000 degrees Celsius. At the surface the temperature is about 5,500 degrees Celsius. A small amount of the Sun's energy reaches Earth as light and thermal energy.