Legacy Astronomical Images > Solar System Series > Sun Unit
The Sun is one of more than 100 billion stars in our galaxy, located at the center of our Solar System. The Sun weighs about 2x1030 kilograms, and is about 1.4x109 meters in diameter. It is composed of about 75% Hydrogen and 25% Helium by mass. Through a series of nuclear reactions in the Sun's core, Hydrogen atoms are fused to to Helium molecules. The energy released by these reactions produces an outward force which balances the inward force of the Sun's own gravity. The temperature in the core is 1.5x107 Kelvin, while the temperature on its surface is 5800 Kelvin.