Chapter 20 Section 2: The Sun Key Concepts: What are the three layers of the sun’s interior? What are the three layers of the sun’s atmosphere? What features form on or above the sun’s surface? Key terms: core, nuclear fusion, radiation zone, convection zone, photosphere, chromosphere, corona, solar wind, sunspot, prominence, solar flare

The sun’s interior The sun’s interior consists of the core, the radiation zone, and the convection zone

The sun’s core The core is the central region The sun produces a lot of energy in the core (from nuclear fusion) Nuclear fusion occurs at high temperature and pressure The total mass of He produced by nuclear fusion is slightly less than the H that goes in. The mass lost is gained in energy.

Radiation Zone The energy produced in the core moves outward through the middle layer, or radiation zone It is a region of very tightly packed gas where energy is transferred mainly as electromagnetic radiation. Very dense. Energy can take 100,000 years to move through it.

Convection Zone The outermost layer of the sun’s interior. Hot gases rise from the bottom and cool toward the top. Cooler gases sink.

Sun‘s atmosphere Includes the photosphere, chromosphere, and corona

Photosphere Inner layer of the atmosphere. It means sphere that gives off visible light Considered the sun’s surface layer

Chromosphere Middle layer of the atmosphere Means “color sphere”

Corona Means “crown” in latin Outer layer of the atmosphere Extends into space for millions of kilometers Gradually thins into electrically charged particles called the solar wind

Features on the Sun Features on or just above the sun’s surface include sunspots, prominences, and solar flares.

Sunspots Look like dark spots on the sun Sunspots are areas of gas on the sun’s surface that are cooler than the gas around them.

Prominences Sunspots usually occur in groups Huge, reddish loops of gas called prominences often link different parts of sunspot regions.

Solar flares Sometimes the loops in sunspot regions suddenly connect, releasing large amounts of magnetic energy. The energy heats gas on the sun, causing the gas to erupt. The eruption is called a solar flare

Solar wind Solar flares can increase solar wind. Usually, Earth’s magnetic field blocks the particles Near N. and S. poles, though, particles enter Earth’s atmosphere and create electric currents. We call these auroras.