The sun is the central part of Earth’s solar system, or the system of heavenly bodies that travel around the sun. It is a huge ball of hot gases that measures about 1.4 million km in diameter and is therefore about 110 times bigger than Earth. It is a medium-sized star that shines with a yellow light and is only one of millions and millions of stars in the universe. It appears to be so much bigger than other stars only because Earth is so much nearer to it than to other stars. The temperature on its surface is at about 5500°C while that of its core is at about 15 500 000°C. On the other hand, Earth’s surface temperature is only at 20°C.