Class notes
Astr 112 Exam 2 Prep Notes
- Course
- ASTR 114
- Institution
- State University Of New York - Binghamton
Detailed and comprehensive exam Preparatory Notes on Exam 2 for Astr 114. *Essential Study Material!!
[Show more]
Content preview
LECTURE 10
Physical properties of the sun
● Interior structure of the Sun:
● Outer layers are not to scale
● The core is where nuclear fusion takes place
● Luminosity—total energy radiated by the Sun— can be calculated from the
fraction of that energy that reaches Earth.
● Solar constant—the amount of Sun's energy reaching Earth—is 1400 W/m2.
● Total luminosity is about 4 × 1026 W—the equivalent of 10 billion 1-megaton
nuclear bombs per second.
● Radius—6.9x108m (109 x Earth)Mass—1.99x1030kg (300,000 Earths)
How is the Sun Stable If All this Radiation is Given Off?
● Weight Of Upper Layers compresses lower layers.
The Solar Interior – Gravitational Equilibrium
● Mathematical models, consistent with observation and physical principles,
provide information about the Sun’s interior
● In equilibrium, inward gravitational force must be balanced by outward
pressure
The Solar Interior – Energy Balance
● Energy Balance:
○ Therateat which energy radiates from the surface of the Sun must be the
same as the rate at which it is released by fusion in the core.
● Solar wind:
○ A flow of charged particles from the surface of the Sun
● Corona: Outermost layer of solar atmosphere
○ ~1 million K
● Chromosphere: Middle layer of solar atmosphere
○ ~ 104–105 K
● Photosphere: Visible surface of Sun
○ ~ 6000 K
● Convection Zone: Energy transported upward by rising hot gas
● Radiation Zone: Energy transported upward by photons
● Core: Energy generated by nuclear fusion
○ ~ 15 million K
Review
● Why does the Sun shine?
○ Chemical and gravitational energy sources could not explain how the Sun
could sustain its luminosity for more than about 25 million years.
, ○ The Sun shines because gravitational equilibrium keeps its core hot and
dense enough to release energy through nuclear fusion.
● What is the Sun's structure?
○ From inside out, the layers are:
• Core
• Radiation zone
• Convection zone • Photosphere
• Chromosphere
• Corona
Nuclear fusion in the sun
● Fission
○ Big nucleus splits into smaller pieces.
○ (Example: nuclear power plants)
● Fusion
○ Small nuclei stick together to make a bigger one.
○ (Example: the Sun, stars)
● High temperatures enable nuclear fusion to happen in the core.
● • The Sun releases energy by fusing four hydrogen nuclei into one helium
nucleus.
● The proton–proton chain is how hydrogen fuses into helium in the Sun.
○ IN- 4 protons
○ OUT- 4He nucleus 2 gamma rays 2 positrons 2 neutrinos
○ Total mass is 0.7% lower.
Solar energy transport
● Energy transport: The radiation zone is relatively transparent;;the
coolerconvection zone is opaque
Random photon walk
● Energy gradually leaks out of the radiation zone in the form of randomly
bouncing photons.
Granulation of the Sun – Evidence of Convection
● Convection (rising hot gas) takes energy to the surface.
● Bright blobs on photosphere show where hot gas is reaching the surface.
Review
● How does nuclear fusion occur in the Sun?
○ The core's extreme temperature and density are just right for nuclear
fusion of hydrogen to helium through the proton–proton chain.
○ Gravitational equilibrium acts as a thermostat to regulate the core
temperature because fusion rate is very sensitive to temperature.
● How does the energy from fusion get out of the Sun?
○ Randomly bouncing photons carry energy through the radiation zone.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller anyiamgeorge19. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $9.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
72042 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now