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Chapter 14 Concept Quiz Mastering Astronomy
Terms in this set (32)
In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot as a result of gravitational contraction. What was the major drawback to this idea?
It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.
When is (was) gravitational contraction an important energy generation mechanism for the Sun?
It was important when the Sun was forming from a shrinking interstellar cloud of gas.
What do we mean when we say that the Sun is in gravitational equilibrium?
There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
What do we mean when we say that the Sun is in energy balance?
The amount of energy released by fusion in the Sun's core equals the amount of energy radiated from the Sun's surface into space.
Which of the following is the best answer to the question, "Why does the Sun shine?"
As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.
How does the Sun's mass compare to Earth's mass?
The Sun's mass is about 300,000 times the mass of the Earth.
Which of the following best describes why the Sun emits most of its energy in the form of visible light?
Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light.
The Sun's surface seethes and churns with a bubbling pattern. Why?
We are seeing hot gas rising and cool gas falling as a result of the convection that occurs beneath the surface.
Which of the following correctly compares the Sun's energy generation process to the energy generation process in human-built nuclear power plants?
The Sun generates energy by fusing small nuclei into larger ones, whereas our power plants generate energy by the fission (splitting) of large nuclei.
Every second, the Sun converts about 600 million tons of hydrogen into 596 million tons of helium. The remaining 4 million tons of mass is _________.
converted to an amount of energy equal to 4 million tons times the speed of light squared
Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?
Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.
If the Sun's core suddenly shrank a little bit, what would happen in the Sun?
The core would heat up, fusion rates would increase, the core would re-expand.
Why does the Sun emit neutrinos?
Fusion in the Sun's core creates neutrinos.
If the Sun suddenly stopped emitting neutrinos, what might we infer (after checking that our neutrino detectors were still operational)?
Fusion reactions in the Sun have ceased within the past few minutes.
Which of the following best explains why the Sun's luminosity gradually rises over billions of years?
Fusion gradually decreases the number of independent particles in the core, allowing gravity to compress and heat the core, which in turn increases the fusion rate and the Sun's luminosity.
Why do sunspots appear dark in pictures of the Sun?
They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.
How can we best observe the Sun's chromosphere and corona?
The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.
The intricate patterns visible in an X-ray image of the Sun generally show _________.
extremely hot plasma flowing along magnetic field lines
How can we measure the strength of magnetic fields on the Sun?
By looking for the splitting of spectral lines in the Sun's spectrum.
Satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because _________.
Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits
Which of the following choices is not a way by which we can study the inside of the Sun?
We can send a space probe into the Sun's photosphere.
A computer salesman attempts to convince you to purchase a "solar neutrino shield" for your new computer. (It's even "on sale!") Why do you turn down this excellent offer?
Neutrinos rarely, if ever, interact with your computer.
A (picture of sun with green arrows pointing towards core and red arrows pointing away from core)
The arrows in this diagram are meant to show how gravitational equilibrium works in the Sun. What do the different colors and different arrow lengths represent?
Green arrows represent gravity; red arrows represent pressure; longer arrows represent a stronger push or pull.
B (picture of orange ball with a few black specks on it)
What layer of the Sun are we seeing in this photo?
C (same picture with an arrow pointing to one of the black specks)
The dark spots in this photo (such as the one indicated by the arrow) represent what we call _____________.
D Which photo pair shows Earth correctly scaled in comparison to the Sun?
the one where Earth is a tiny spot the size of a sunspot next to the Sun
E (a bright orange and yellow area with bright white spots surrounded by a web of orange and yellow darker areas with an arrow pointed to one of the bright white areas)
This photograph shows a small portion of the Sun's photosphere. What is going on in the bright regions (such as the bright region indicated by the arrow)?
Hot gas is rising up from the solar interior.
F (a dark background with red loops rising from and falling towards the surface with an arrow pointing to an area where the red is coming from on the surface)
This X-ray image shows a loop of hot gas above the surface of the Sun. If we took a visible light photo that looked in the Sun's photosphere just under the two points where the loop of gas comes down (arrows), what would we find?
G (same image)
Look again at the loop of hot gas in this X-ray image. Suppose we took another photo looking at the same place 1 hour later. What would we see?
The loop would look about the same as it does in this photo.
H (dark photo of the sun showing red wisps and patches surrounding brighter yellow flame-like spots coming from the surface)
What layer of the Sun are we seeing in this photograph, and in what wavelength band was it photographed?
corona, photographed in X rays
I (same image)
What do the yellow regions represent in this photograph?
regions where hot gas is emitting a lot of X rays
J (graph; y-axis: Percentage of Sun's surface covered by sunspots (0.0, 0.5); x-axis: year (1900, 2010); graph zig-zags up and down in regular approximate 11-year intervals)
Study this figure and its axis labels. What is this graph showing us?
The number of sunspots on the Sun tends to increase and decrease with an approximately 11-year cycle.
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