Earth and Space Science / Unit 9: The Solar System
9.2 The Sun
Notes
The Sun is an average star, a ball of hot plasma that makes up 99.8% of the solar system's mass.
- Energy comes from nuclear fusion in the core: hydrogen nuclei fuse into helium, converting a little mass into energy ($E = mc^2$). Core temperature is about 15 million °C.
- Layers: core, radiative zone, convective zone, then the photosphere (visible surface, about 5,500°C), chromosphere, corona.
- Sunspots are cooler dark patches; the sunspot cycle is about 11 years. Solar flares and coronal mass ejections can disturb satellites and cause auroras.
- The Sun has fused hydrogen for about 4.6 billion years and has about 5 billion more.
Practice
The Sun produces energy by:
Fusion in the core powers the Sun.
Sunspots appear dark because they are:
They are about 1,500°C cooler.
The visible surface of the Sun is called the:
The photosphere gives the light we see.
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