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4.5 billion years

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According to modern science, approximately how old is the Sun?

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When a star contracts in size, gravitational potential energy is converted to thermal energy.

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Which of the following correctly describes how the process of gravitational contraction can make a star hot?

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nuclear fusion

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The source of energy that keeps the Sun shining today is _________.

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gravitational force and outward pressure

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What two physical processes balance each other to create the condition known as gravitational equilibrium in stars?

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the rate at which fusion generates energy in the Sun's core and the rate at which the Sun's surface radiates energy into space

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Energy balance in the Sun refers to a balance between _________.

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core, radiation zone, convection zone, photosphere, chromosphere, corona

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From center outward, which of the following lists the "layers" of the Sun in the correct order?

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photosphere

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Which of these layers of the Sun is coolest?

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GREATEST: corona, chromoshere, photosphere, convection zone, radiation zone, core LEAST

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Listed following are the different layers of the Sun. Rank these layers based on their distance from the Sun's center, from greatest to least.

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HIGHEST DENSITY: core, radiation zone, convection zone, photosphere, chromosphere, corona LEAST DENSE

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Rank the layers of the Sun based on their density, from highest to lowest.

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HIGHEST: core, radiation zone, convection zone, photosphere LOWEST

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Rank the following layers of the Sun based on their temperature, from highest to lowest.

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HIGHEST: core, radiation zone, convection zone, photosphere LOWEST

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Rank the following layers of the Sun based on the pressure within them, from highest to lowest.

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core

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In which of the following layer(s) of the Sun does nuclear fusion occur?

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photosphere, chromosphere, corona

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Which of the following layers of the Sun can be seen with some type of telescope? Consider all forms of light, but do not consider neutrinos or other particles.

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Corona, chromosphere, photosphere

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Following are the different layers of the Sun's atmosphere. Rank them based on the order in which a probe would encounter them when traveling from Earth to the Sun's surface, from first encountered to last.

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photosphere, chromosphere, corona

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Rank the layers of the Sun's atmosphere based on their density, from highest to lowest.

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corona, chromosphere, photosphere

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Rank the layers of the Sun's atmosphere based on their temperature, from highest to lowest.

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corona, chromosphere, photosphere

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Rank the layers of the atmosphere based on the energy of the photons that are typically emitted there, from highest to lowest.

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core

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Nuclear fusion of hydrogen into helium occurs in the _____

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convection zone

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Energy moves through the Sun's ______ by means of the rising of hot gas and falling of cooler gas.

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photosphere

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Nearly all the visible light we see from the Sun is emitted from the ______

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chromosphere

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Most of the Sun's ultraviolet light is emitted from the narrow layer called the _______ where temperature increases with altitude.

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corona

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We can see the Sun's ________ most easily during total solar eclipses.

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radiation zone

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The ______ is the layer of the Sun between its core and convection zone.

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4 H becomes 1 He + energy

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The overall result of the proton-proton chain is that __________.

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use computer models to predict interior conditions

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To estimate the central temperature of the Sun, scientists _________.

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If the Sun's core were a bit hotter, the fusion rate would increase. This would produce more energy, which would cause the core to expand slightly and cool. The cooling would cause the fusion rate to slow back down until the Sun was back to the original size and temperature and fusion occurred at the original rate.

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How does a natural "solar thermostat" keeps the core fusion rate steady in the Sun?

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Photons take (HUNDREDS OF THOUSANDS OF YEARS) to get out of the Sun because their paths (ZIGZAG REPEATEDLY) . Because the plasma is so (DENSE) in the Sun's interior, a photon can travel (A FRACTION OF A MILLIMETER) before colliding with an electron and deflecting into a new direction.

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How does energy generated by fusion makes its way to the Sun's surface. How long does it take? (FILL IN THE BLANK)

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Mathematical models use the observed composition and mass of the Sun along with the laws of physics to derive equations that describe the gravitational equilibrium, solar thermostat, and rate at which energy moves from the core to the photosphere.

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How do mathematical models help us learn about conditions inside the Sun?

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We can check the models by comparing their predictions for radius, surface temperature, and luminosity, as well as other observable parameters generated by studying helioseismology. The models do indeed make predictions that allow us to explain these observations; we are on the right track.

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How can we be confident that the models are on the right track?

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four individual protons

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Which of these groups of particles has the greatest mass?

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mathematical models of the Sun.

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Scientists estimate the central temperature of the Sun using

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helium, energy, and neutrinos.

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At the center of the Sun, fusion converts hydrogen into

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photons

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Solar energy leaves the core of the Sun in the form of

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We would be able to tell that fusion reactions had ceased because we would no longer detect neutrinos from the Sun. Neutrinos, a by-product of nuclear fusion, exit the Sun immediately.

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Choose the correct description, of how would we be able to tell, if fusion reactions in the Sun were to suddenly cease.

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Introduction: The source of the Sun's energy was a mystery for thousands of years, but today we think we have a very good understanding of how the Sun works and why it shines so steadily. This activity will help you appreciate how we have developed this understanding of the Sun through a combination of observations and theoretical modeling.

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Learning Goal: To understand the interplay between observations and theoretical modeling in our current scientific understanding of the Sun.

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OBSERVATION: The photosphere is made mostly of hydrogen and helium;The photosphere emits mostly visible light; The corona is hotter than the photosphere; The Sun emits neurtrinos INFERENCES: The Sun generates energy by fusing hydrogen into helium;The core temperature is 10 million k; The convection zone is cooler than the radiation zone;The composition of the photosphere is the same as that the gas cloud that have birth to our solar system.

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To understand the interplay of observations and models you must first be able to distinguish between things that we observe and things that we infer from models. Consider the following statements about the Sun. Classify each statement as an observation or as an inference based on the current, accepted model for the Sun.

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The corona primarily emits X rays while the photosphere primarily emits visible light.

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One statement about the Sun from Part A is "The corona is hotter than the photosphere." Which of the following statements provides observational evidence for this claim?

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We can calculate it by applying Newton's version of Kepler's third law with Earth's orbital period (1 year) and Earth's average distance from the Sun (1 AU).

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Now consider the statements in Part A that are inferred from models. A solar model is used to calculate interior conditions based on certain "known" characteristics of the Sun, such the Sun's total mass. How do we know the Sun's mass?

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Measurements of the Sun's total energy output into space Observations of neutrinos coming from the Sun

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A solar model is used to calculate the expected temperature and density at all depths within the Sun. These results are then used to calculate the expected fusion rate within the Sun. We have confidence that the model is correct because it agrees with the observed characteristics of the Sun. Which of the following observations can be used to check that we really do know the Sun's internal fusion rate?

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-An increase in the core temperature -A decrease in the core radius

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Which of the following changes would cause the fusion rate in the Sun's core to increase?

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-If the fusion rate initially increases, then the core expands. -If the fusion rate initially decreases, then the core contracts.

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Which of the following must occur for a star's core to reach equilibrium after an initial change in fusion rate?

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The Sun's core would start to heat up, and the rate of fusion would increase even more.

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What would happen if the fusion rate in the core of the Sun were increased but the core could not expand?

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Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.

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How is the sunspot cycle directly relevant to us here on Earth?

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This statement is sensible. Solar flares can cause havoc with satellites, communication networks, and power grids because of the energetic charged particles released.

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News of a solar flare caused concern among businesses involved in communication and electrical power generation. Choose the correct explanation of whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false).

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They are cooler than their surroundings.

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Why do sunspots appear darker than their surroundings?

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SOLAR MAXIMUM: solar flares are most common; sunspots are most numerous on the Sun; auroras are most likely in Earth's skies; occurs about 11 years after a solar maximum (on average); orbiting satellites are most at risk SOLAR MINIMUM: occurs about 5 to 6 years after a solar maximum (on average)

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Listed following are events or phenomena that occur during either the part of the sunspot cycle known as solar minimum or the part known as solar maximum. Match these items to the correct part of the sunspot cycle.

ASTRO WK TWO Mastering Astronomy Chp 14 – Flashcards

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