The Sun's Energy and Structure

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Questions and Answers

What is the primary source of energy that allows the Sun to shine for billions of years?

  • Nuclear potential energy (correct)
  • Gravitational potential energy
  • Chemical energy
  • Thermal energy

What does gravitational equilibrium in the Sun help maintain?

  • A stable chemical composition
  • Continuous expansion of solar mass
  • Balance between gravity and fusion pressure (correct)
  • Increased surface temperature

How long can the chemical energy content of the Sun sustain its luminosity?

  • 10,000 years (correct)
  • 10 billion years
  • 1 billion years
  • 25 million years

What ensures that the Sun is not contracting over time?

<p>Energy produced by nuclear fusion (A)</p> Signup and view all the answers

Which of the following statements is NOT true about the Sun's luminosity?

<p>It is balanced by gravitational potential energy. (B)</p> Signup and view all the answers

What is the significant fate of the Sun given its current energy source?

<p>It will shine for around 10 billion years total. (B)</p> Signup and view all the answers

Which is the correct relationship concerning the Sun's energy balance?

<p>Energy radiated equals energy from the nuclear fusion process. (A)</p> Signup and view all the answers

What is the particle that fuses into helium in the Sun?

<p>A proton (B)</p> Signup and view all the answers

What product is formed when four protons fuse together in the Sun?

<p>One helium nucleus (D)</p> Signup and view all the answers

Why can the Sun be classified as in hydrostatic equilibrium?

<p>The outward pressure from nuclear fusion balances the weight of outer layers. (D)</p> Signup and view all the answers

Which equation describes the energy released during the fusion of hydrogen into helium?

<p>E = mc^2 (B)</p> Signup and view all the answers

What is the primary source of energy that allows the Sun to shine?

<p>Nuclear fusion (B)</p> Signup and view all the answers

How much energy is approximately released when four protons fuse into one helium nucleus?

<p>4 x 10^-12 J (C)</p> Signup and view all the answers

Which layer of the Sun is where nuclear fusion occurs?

<p>Core (D)</p> Signup and view all the answers

What happens to the core of the Sun when the temperature declines?

<p>Fusion rate drops and core contracts (C)</p> Signup and view all the answers

At what temperature does the Sun's corona exist?

<p>1 million K (C)</p> Signup and view all the answers

What mechanism primarily transports energy through the radiation zone?

<p>Photons (A)</p> Signup and view all the answers

What byproducts are released alongside the helium nucleus during fusion?

<p>Neutrinos, gamma rays, and positrons (B)</p> Signup and view all the answers

Why is there a decrease in total mass during the fusion of protons into helium?

<p>Mass is converted entirely into energy (C)</p> Signup and view all the answers

How long does it take for the Sun to rotate once at its equator?

<p>25 days (D)</p> Signup and view all the answers

What is the approximate radius of the Sun compared to Earth?

<p>109 times (A)</p> Signup and view all the answers

What is the primary fuel for nuclear fusion in the Sun?

<p>Hydrogen (C)</p> Signup and view all the answers

Which of the following correctly describes the photosphere?

<p>It is where the plasma becomes transparent. (B)</p> Signup and view all the answers

What defines the solar wind?

<p>A flow of charged particles from the Sun's surface (D)</p> Signup and view all the answers

What is one method used to understand the interior of the Sun?

<p>Observing solar vibrations (B)</p> Signup and view all the answers

How does gravitational equilibrium affect nuclear fusion in the Sun?

<p>It regulates the core temperature. (C)</p> Signup and view all the answers

What role do solar neutrinos play in studying the Sun?

<p>They inform about the Sun's core processes. (B)</p> Signup and view all the answers

What is the primary cause of energy transport in the radiation zone of the Sun?

<p>Randomly bouncing photons (D)</p> Signup and view all the answers

What problem was encountered in early searches for solar neutrinos?

<p>The predicted number was not found. (B)</p> Signup and view all the answers

What is suggested by the agreement between mathematical models and observations of solar vibrations?

<p>The models accurately represent the Sun's interior. (A)</p> Signup and view all the answers

What process occurs in the core of the Sun?

<p>Nuclear fusion of hydrogen into helium (C)</p> Signup and view all the answers

What does hot plasma do in the convection zone of the Sun?

<p>It rises to convey energy to the photosphere. (B)</p> Signup and view all the answers

What causes solar activity?

<p>Stretching and twisting of magnetic field lines near the Sun's surface (C)</p> Signup and view all the answers

How frequently does solar activity rise and fall?

<p>In a 11-year cycle (C)</p> Signup and view all the answers

What force prevents the particles in a star from flying apart?

<p>Gravity (D)</p> Signup and view all the answers

What contributes to a star not collapsing?

<p>Pressure from radiation and heat in the core (A)</p> Signup and view all the answers

What would likely happen if the rate of hydrogen fusion in a star were to increase?

<p>The star would expand (B)</p> Signup and view all the answers

For a star to maintain equilibrium, there must be a balance between the rate of energy generated and the energy lost, specifically related to what?

<p>Energy generation and luminosity (B)</p> Signup and view all the answers

Which of the following statements about solar activity is true?

<p>Solar activity has an 11-year cycle of variation (B)</p> Signup and view all the answers

What is NOT a cause of solar activity?

<p>Gravitational pull from nearby stars (C)</p> Signup and view all the answers

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Study Notes

Sun's Energy Source

  • The Sun's energy is not from fire or contraction
  • The Sun shines because of nuclear fusion in its core
  • Nuclear fusion converts hydrogen into helium, releasing a huge amount of energy
  • The process is called the proton-proton chain

Sun's Stability

  • The Sun is in gravitational equilibrium, where the force of gravity inward is balanced by the outward pressure from the hot gas
  • The Sun maintains its energy balance because fusion in the core provides energy at the same rate it radiates outwards
  • The Sun's core temperature is about 15 million Kelvin

Sun's Structure

  • The Sun has a layered structure, with each layer having different properties
  • core: where nuclear fusion happens, producing the Sun's energy
  • radiation zone: energy is transported outward by photons
  • convection zone: energy is transported upward by rising hot gas
  • photosphere: visible surface of the Sun, where the plasma becomes transparent
  • chromosphere: middle layer of the solar atmosphere
  • corona: outermost layer of the solar atmosphere

Sun's Properties

  • Radius: 6.9 x 10^8 meters (109 times Earth)
  • Mass: 2 x 10^30 kg (300,000 Earths)
  • Luminosity: 3.8 x 10^26 watts
  • Rotation: 25 days at the equator, 30 days at the poles

Solar Activity

  • Solar activity is caused by stretching and twisting of magnetic field lines near the Sun's surface
  • Solar activity varies with an 11-year cycle

Solar Thermostat

  • The Sun acts as a thermostat, regulating its core temperature
  • If the core temperature decreases, the fusion rate drops, causing the core to contract and heat up
  • If the core temperature increases, the fusion rate rises, causing the core to expand and cool down.

Understanding the Sun’s Interior

  • Solar vibrations can be observed, providing information about the Sun's internal structure
  • Solar neutrinos are created during fusion and travel directly through the Sun, providing insights into the core
  • Mathematical models of the Sun's interior match observations of solar vibrations and neutrinos

Energy Escape from the Sun

  • Energy from the core takes a long time to escape the Sun
  • Photons randomly bounce through the radiation zone, carrying energy outward
  • Hot plasma rises in the convection zone, carrying energy to the photosphere

Solar Neutrinos

  • Early observations of solar neutrinos found fewer neutrinos than predicted
  • Later observations found more neutrinos, but some had changed form

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