Download Unit 3 : The Sun A. Layers of the Sun 1. Core 2. Radiation zone 3

Unit 3 : The Sun
A. Layers of the Sun
1. Core
2. Radiation zone
3. Convection zone
4. Photosphere – visible surface of the sun
– lower atmosphere
5. Chromosphere – thin layer of hot gases –
middle atmosphere
6. Corona – outer weak layer of the
solar atmosphere
B. Sun’s life cycle
1. Starts with large cloud of gas and dust – mainly of hydrogen
2. Nuclear fusion occurs and cloud of gas becomes the Sun
3. Later (billions of years) all the hydrogen gets consumed into helium which will
cause the sun to collapse
4. Sun will expand much larger than it was earlier in its lifetime and will become a
Red Giant (large, cool star of high luminosity)
5. Core will stabilize while the rest of its outer regions continue to expand and are
shed off
6. Core will be a white dwarf – a star that has exhausted all of its nuclear fuel and
has collapsed = final stage of evolution
7. Outer regions will be planetary nebula (glowing shell of gas)
C. Solar Energy becomes Chemical Energy
1. plants take in sunlight, carbon dioxide,
and water to create glucose (sugar) and
releases oxygen = photosynthesis
2. solar energy is called photons
3. glucose is used to make energy for all
living things
D. Nuclear Reactions
1. Fusion – process that produces radiant energy within the sun by colliding 2
atomic nuclei
2. Fission – splitting of something into 2 or more parts
3. Combustion – a burning reaction which causes sun to produce light
E. Forms of Energy Produced by the Sun
1. the sun is the ultimate source of energy for every living thing
2. the sun emits a spectrum of electromagnetic energy which includes UV rays,
visible light, and heat
3. solar energy reaches the Earth as radiation
4. X-rays and cosmic rays are filtered by the atmosphere
F. Energy Flow from the Sun
1. A thermonuclear fusion reaction from the sun’s interior converts hydrogen into
helium which releases a huge amount of energy (therm = heat)
2. the energy created by this fusion reaction creates heat (thermal energy) which
travels through space in the form of electromagnetic waves
3. electromagnetic waves allows the transfer of heat through a process known as
radiation
4. there are different types of radiation depending on the size of the wavelength
a. examples include : gamma rays, X rays, UV rays, and visible light
G. Magnetic Field
1. about 50% of the solar energy that
strikes the top of the atmosphere reaches
the Earth’s surface and is absorbed
2. most of this energy stays in the sky
3. water vapor and carbon dioxide
(greenhouse gases) are the major
absorbing gases that absorb solar radiation
4. there is a strong magnetic field generated
by the movement of the Earth’s liquid
outer core
5. this magnetic field protects the planet
from the harmful effects of radiation
H. Heating of Earth’s Surface
1. how hot the Earth’s surface is determines the temperature of the air above it
2. different land surfaces absorb differing amounts of incoming solar energy
3. land heats more rapidly and to a higher temperature than water
4. land cools more rapidly and to a lower temperature than water
5. it takes more thermal energy (heat energy) to change the temperature of
water, therefore water has a smaller temperature range