Sun

The Sun is a fairly ordinary star which formed in an open star cluster about 4.65 billion years ago. The only major difference between the Sun and any other star is that we live near it, so it looks much bigger and brighter than the others. However there are some features of the Sun which might have made it more likely than most stars to be the host to a planet (Earth) which was the home to life.

Firstly the Sun is rather rich in heavy atoms. Secondly it is unusual in having an almost circular orbit round the Milky Way Galaxy, about 28000 light-years from the center of the Galaxy. Thirdly it is a fairly stable star. We do not know which if any of these factors was important in the origin of life.

The Sun, like all other stars, is a nuclear fusion reactor. Every second our Sun changes 4 billion kilograms of protons into light energy. (Imagine 4 bags of sugar a thousand times too big in each direction!). So far the Sun has only used up half its hydrogen fuel, so it should last for at least another 4 billion years before it turns into a red giant, and destroys the inner planets including the Earth.

The nearest star to the Sun is Proxima Centauri, which is about 4.25 light-years away. This is typical of the distance between stars in the spiral arms of the Galaxy.

If the Solar System was shrunk to the size of a penny (the PennySystem) then Proxima Centauri would be only 10 centimeters away.

Image of Sun courtesy of SOHO(an international cooperation between ESA and NASA)