G2 Variable

4,600 million Years

150 Million Kilometres (1 AU)

26.8 days

695,000 Kilometres

71% Hydrogen [H]

26.5% Helium [He]

2.5% Other

1.99 x 10³⁰ Kilograms

6,000^o C

15 million^o C

3.83 x 10³³ ergs / second

0.137Watts / cm²

7.25^o

The Sun is our closest star and the centre of the Solar System.  It's four and a half thousand million years old and in 6 thousand million years or so, it is predicted that it will finally die. Right now it's an average sized star, but just a pinhead of the Sun's raw material could kill a person 160 kilometres away. Each second the Sun loses 4.5 million tonnes of material - this means that in 42 million years it would lose enough material to make the Earth. To give you an idea of its size, it's 333,400 times bigger than the Earth and contains 99.86% of the mass of the entire Solar System - this means Jupiter and all the other planets and asteroids only make up 0.14% of the mass of the Solar System!  All light we see from the Sun comes from a layer 500km deep (the top 0.1%) and takes about 8.3 minutes to reach us down here on Earth.

The Sun is now slowly increasing its luminosity, burning hydrogen in its core, converting it into Helium, but it can only keep that up for another four thousand million years or so, when it will run out of Hydrogen.   When this happens the core will shrink and the Sun will expand and get hotter, engulfing Mercury and nearly reaching Venus. As it does so, the core will reach a blistering 100 million°C and will begin to burn the Helium there. This will keep the star stable as a 'Red Giant' for a thousand million years or so until the Helium runs out.   When this happens, the core will begin collapsing again and it'll get hotter and the star will get bigger once more, expanding to the present orbit of Earth. At this point, the Sun will be very unstable, expanding and shrinking often and losing a lot of material into space. Soon, all that is left will be its inner Carbon core, which, although it will still contain about 2 thirds of the Sun's mass, will be collapsed so much that it will have reached the ultimate density, Quantum forces will stop it collapsing further and it'll become a 'White Dwarf' - a small star about the size of the Earth but much denser (about 1cm³ of this stuff would have the mass of a tonne - that's a million times the density of water!)