Here Comes the Sun!! Chapter 14 Section 2 Page 545 Miss Sullivan Rm B2

The Sun The sun is the closest star to Earth It is approximately 93 million miles or 150 million kilometers away (1 astronomical unit) It provides almost all of the energy for life on Earth It also accounts for 99.8% of the total mass of our solar system

The Sun’s Energy The sun’s energy is produced through nuclear fusion. Nuclear fusion is when two smaller atomic nuclei (hydrogen) are fused or joined together to form a more massive nucleus (helium) and releasing energy. This fusion happens only under intense pressure and temperature

Nuclear Fusion During nuclear fusion, two atomic nuclei collide and fuse.

Forces in Balance Nuclear fusion in the sun’s core produces an incredible amount of energy. This energy causes gas ions within the sun to move very fast, generating a tremendous pressure pushing outward from the core. This pressure would cause the sun to explode if it weren’t balanced by an equal and opposite force The balancing force is gravity. The weight of matter pushing inward and the outward pushing pressure are balanced throughout the sun.

The Layers of the Sun The sun has an interior and an atmosphere, each of which consists of several layers.

The Sun’s Interior Convection Zone --- where hot gases form convection currents Radiation Zone --- a place of condensed gases that transfer electromagnetic radiation The Core --- where nuclear fusion takes place

The Sun’s Atmosphere The sun’s atmosphere has 3 layers: The Photosphere the sphere that “gives off light” The Chromosphere a thin layer of color The Corona the outer white halo that extends millions of kilometers into space

The Sun Features on or above the sun include sunspots, prominences, and solar flares.

Sunspots Sunspots look like small dark areas on the sun’s surface (some are actually as big as the Earth!) Sunspots are areas of gas on the sun that are cooler than the gases around them. Cooler gases don’t give off as much light as the hotter gases. Sunspots actually occur in cycles and can be linked with weather here on Earth!

Sunspots and Weather Evidence that supports that theory that sunspots cycles influence weather include: Little Ice Age: most parts of the world experienced cold harsh weather. Little Ice Age is associated with low sunspot activity between 1645-1715 (these are called minimums) Low sunspot activity occurs every 500 years, perhaps another Little Ice Age will occur in 2050! (41 years from now…how old will you be?)

Prominences Prominences: Reddish loops of ionized gas that link different parts of sunspot regions.

Solar Flares Solar Flares: When prominences suddenly connect, a large amount of energy is released causing huge explosions of hydrogen (Solar Flares)

Solar Wind Solar flares cause an increase in solar wind that extends the corona into space An increase is solar winds can cause electromagnetic effects on Earth: auroras, disrupt communications, cause electrical problems

Homework Read Chapter 14, Section 2 Do the questions at the end of the section, page 550