1. 2. Our favourite star The Sun photographed in soft X-rays

2. The Sun’s stats Distance:1 AU=150 million km Distance:1 AU=150 million km Radius: 700,000 km Radius: 700,000 km Mass: 2 x 10 30 kg Mass: 2 x 10 30 kg Average density:1.4 kg/litre Average density:1.4 kg/litre Surface temperature:5,800 K Surface temperature:5,800 K Luminosity:3.9 x 10 26 watts. Luminosity:3.9 x 10 26 watts.

3. It gives us life and energy Humans have always revered the Sun Humans have always revered the Sun But where did it get its energy from? But where did it get its energy from? If it were coal it would only last 10,000 years! If it were coal it would only last 10,000 years!

4. Atkinson, 1920: The Sun’s energy comes from the fusion of hydrogen nuclei to helium The forces between nucleons are about 100,000,000 times as strong as those between atoms. The forces between nucleons are about 100,000,000 times as strong as those between atoms.

5. This means that the energy involved in nuclear reactions will be hundreds of millions times greater than that involved in chemical reactions This means that the energy involved in nuclear reactions will be hundreds of millions times greater than that involved in chemical reactions The Sun would last nearly 100 billion years on its hydrogen fuel – but other processes will cause problems before then! The Sun would last nearly 100 billion years on its hydrogen fuel – but other processes will cause problems before then!

6. We now know a lot about how the Sun works from computer models based on the laws of physics. We now know a lot about how the Sun works from computer models based on the laws of physics.

8. The corona, the source of the solar wind becomes visible in an eclipse. The corona, the source of the solar wind becomes visible in an eclipse.

9. The solar wind brings us auroras. The solar wind brings us auroras.

10. Sunspots are the result of ‘knots’ in the magnetic field of the Sun. They ‘untie’ every 11 years. Sunspots are the result of ‘knots’ in the magnetic field of the Sun. They ‘untie’ every 11 years.

11. Our insight into the workings of the Sun enables us to understand the stars better …