Sun

100 The Sun is the VIP at the centre of our Solar system. It is infrequently referred to as Sol to distinguish it from other "suns". Planet Earth orbits the Sun, as do a lot of other bodies, including other planets, asteroids, meteoroids, comets and dust. Its heat and light support almost all life on Earth.

The Sun has a mass of about 2×1030kg, which is not at all higher than that of an average star. About 74% of its mass is hydrogen, with 25% helium and the respite made up of trace quantities of heavier rudiments. It is thought that the Sun is about 5 billion years old, and is about half way through its key sequence evolution, during which nuclear fusion reactions in its core fuse hydrogen into helium. In about 5 billion years time the Sun will turn into a planetary nebula.

Although it is the bordering star to Earth and has been intensively studied by scientists, many questions about the Sun remain unanswered, such as why its outer atmosphere has a temperature of over 106 K when its able to be seen surface has a temperature of just 6,000 K.