1. Chapter 11

2. The Sun  average-sized star.  300 000 times more mass than Earth  The sun’s mass results in great pressure and heat at the centre of the Sun cause a thermonuclear reaction  Hydrogen is converted to helium  it has enough hydrogen to last another 5 billion years.

3. The Sun  contains more than 99 percent of all the mass in the solar system  The tremendous radiated energy that is produced keeps Earth warm enough to support life

4. The Sun  Sunspots dark patches on the Sun’s surface that are slightly cooler, about 3500°C, than surrounding areas  Occasionally, extremely violent eruptions of gas called solar flares also occur. These eruptions can last for a few hours and heat gases to 11 000 000°C.

5. The Sun  Sun spots and solar flares are associated with Solar wind.  Exposure to solar wind could be fatal for any organism living on Earth.  Earth’s magnetic field deflects most of the solar wind around the planet

6. The Sun  Some of the high-energy particles in solar wind enter Earth’s atmosphere at the North and South Poles, where they collide with gases in the atmosphere. aurora borealis and aurora australis Northern and Southern Lights

7. The Sun

8. Questions  1-3, 5 -7, 11 page 397