The Sun. Artwork of the Sun, the star at the centre of our solar system. The Sun is a huge ball of hydrogen gas, ionised into a plasma by the immense temperatures generated by nuclear fusion at its core. This fusion is ignited by the immense pressure generated by the Sun's mass. The Sun has a diameter of around 1,392,000 kilometres (equivalent to 109 Earths), a mass 330,000 times that of Earth, and a volume 1.3 million times that of Earth. It is 150 million kilometres from our planet, but its light and heat provide almost all the energy for life on Earth. A solar prominence is seen at upper right.