1 Chapter 1 – Why does the Sun shine?
OpenStax Astronomy Chapter 15: The Sun: A Garden-Variety Star
OpenStax Astronomy Chapter 16: The Sun: A Nuclear Powerhouse
Sun’s Atmosphere
I. The of the Sun
A. Lower gas than in Sun, density with increasing
1. Includes: Photosphere, chromosphere, corona
II.
A. layer where light is
1. Apparent of sun, layer
B. Average temperature Kelvin or °F
1. Known as the “ Temperature” , related to and of star
C. Temperature and density
1. Hotter in layers of photosphere
D. layers some from deeper layers
1. Produces a complex of light
III.
A. Located the photosphere
B. than the photosphere
1. Temperature
2. Heated by field of the Sun
C. Gives off a spectrum
IV.
A. of gas the chromosphere out to
B. Very : 1 to 2 million K
1. Emits
C. Density is very
D. Parts can for several times width of Sun
E. Can only see during eclipse
From hottest to coolest, the layers in the Sun are:
Solar Magnetic Activity
V. of the Sun
A. Sun: see activity involving such as sunspots, flares, loops
1. Sun: ordinary, little activity
2. Magnetic field is caused by particles in the interior
B. : particles flowing from the Sun
1. Passes through , where magnetic field extends away from the Sun
2. Interacts with atmospheres and magnetic fields of other , producing auroras
3. Extends for about times the distance from the Sun to the Earth
VI.
A. areas in the , by about 1500 K
1. Still very , around 4200 K
2. Appear because emit light than regions
B. area surrounded by part
C. where magnetic field loops the photosphere
1. Occur in
D. of sunspots changes on an 11-year
1. When magnetic North and South poles
E. : peak of cycle, sunspots and activity
Sunspots have temperatures about of 4,000 K. Why do sunspots appear to be dark?
VII. Other Sun
A. : loops of bright charged gas in
B. : of hot rising gas in the constrained by magnetic fields
1. Can reach 1 million kilometers high and speeds of 1300 kilometers per second
C. Solar and coronal mass ejections, : Rapid, violent bursts and eruptions of energy and
1. Heat gas to Kelvin
2. Intense X-rays, gamma rays, and ultraviolet
3. CMEs cause particles to the Sun and flow into at high speeds
D. Solar and CMEs can disrupt electric and
1. Cause brilliant
2. Affect astronauts in space
3. Affect ability to navigate by magnetic field
Fusion
VIII. Nuclear
A. Happens in the of all stars
B. Also called , because Hydrogen (H) is the source
1. from chemical burning/fire
C. Makes by combining (H) into ones (Helium)
1. released per in the Sun: 3.85 x 1026 Watts
D. Requires ramming together at speed
1. Protons have electrical charge
2. But “like” charges , so protons are pushed apart by
E. Atomic nucleus held together by
1. Only works at very distances, size of nucleus
F. For : Must get protons enough for nuclear force to them together overcoming the force
1. Need very high to get protons to high enough speeds for fusion
2. Only get high enough temperature in the of stars (15 million Kelvin)
In order for fusion to occur, protons have to get close enough for what to take place?
IX. from Fusion
A. In the sun, Hydrogen (H) atoms turn into Helium
B. This leaves
1. Mass of 4 H nuclei is slightly than 1 He nucleus
C. Einstein’s says and are :
1. c2 is a large number, so a = of energy
D. in mass between H and He is as energy
E. process is also called the
1. process to get from Hydrogen to Helium, releases other particles like neutrinos
2. Primary method of nuclear fusion in the of the
3. Conditions must be (150 times denser than water, 15 million K)
Sun’s Interior
X. Fusion
A. Fusion emits
1. (low mass) atomic particles, charge
2. with matter
3. the core of the Sun (transparent) traveling near speed of light
4. pass through Earth, and you, without interacting
B. Possible to how often solar neutrinos at to learn about
C. agrees with theoretical models of Sun’s and fusion
XI. The Sun’s long-lasting is a matter of
A. of balance:
1. : outward equals inward force of
a. Density, temperature, and pressure toward the
b. Greater must be by increased of gas
c. Keeps the Sun from collapsing or
2. Rate of from its surface equals rate energy in the by fusion
a. Stars are very and can last for billions of years (Sun about 10 billion years)
Where does nuclear fusion take place in the Sun?
XII. Energy
A. processes from the to the of the sun
B. part of the Sun:
1. : energy moved by (photons), photons move out from the core to less crowded regions
2. of the Sun’s interior
C. part:
1. Convection: of hot material ( of hot/cool gas)
2. Too cool and for radiative transfer
D. : energy into space as , radiation again
E. from the takes years to reach the
1. Photons get and reemitted, or
Tutorial Activity – Introduction
1. Tell me a little about yourself. You may want to answer some of the following: What name would you like me to call you? What are some of your interests or hobbies? What are you studying in college?
2. What do you value the most in life?
3. Is there anything you are excited or worried about in taking this course or anything you want me to know?
Tutorial Activity – The Sun
“Elementary Astronomy Worksheet Handout 18: Sun” (modified by Kaisa E. Young) by Catherine Whiting via OER Commons, licensed under CC BY 4.0, https://oercommons.org/courses/elementary-astronomy-worksheets
1. Order the layers of the Sun from inward to outward and briefly describe each layer, including the temperature. (Photosphere, Chromosphere, Core, Corona, Radiative Zone, Convective Zone)
2. List the main types of solar activity and briefly describe them.
3. What do we think causes solar activity?
4. Why do sunspots appear dark? Is there no light being emitted from those regions of the Sun?
5. What causes the sunspot cycle? How long is it?
6. What effects does solar activity have on the Earth, if any?
7. What keeps the sun shining? Briefly describe how the process works.
8. What prevents the sun from collapsing due to its strong gravity?
