Chapter 14 home work 12 The sun

Question 1

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

         10,000 years        
         400 million years.        
         25 million years        
         4 1/2 billion years

Answer 1

4 1/2 billion years

Question 2

The Sun will exhaust its nuclear fuel in about ______.

         5 billion years        
         50 billion years        
         5 million years        
         5000 AD

Answer 2

5 billion years

Question 3

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

     the nuclear force and the electromagnetic force        

     the nuclear force and the gravitational force        
         gravitational force and outward pressure        
         gravitational force and surface tension

Answer 3

gravitational force and outward pressure

Question 4

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

         chemical reactions        
         nuclear fusion        
         nuclear fission        
         gravitational contraction

Answer 4

nuclear fusion

Question 5

What is the Sun made of (by mass)?

         50% hydrogen, 25% helium, 25% other elements        
         100% hydrogen and helium        
         70% hydrogen, 28% helium, 2% other elements        
         90% dark matter, 10% ordinary matter

Answer 5

70% hydrogen, 28% helium, 2% other elements

Question 6

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

         Core, radiation zone, convection zone, photosphere, chromosphere, corona        
         Core, radiation zone, convection zone, corona, chromosphere, photosphere        
         Core, convection zone, radiation zone, corona, chromosphere, photosphere        
         Core, corona, radiation zone, convection zone, photosphere, chromosphere

Answer 6

Core, radiation zone, convection zone, photosphere, chromosphere, corona

Question 7

The Sun’s surface, as we see it with our eyes, is called the _________.

         chromosphere        
         core        
         corona        
         photosphere

Answer 7

photosphere

Question 8

The Sun’s average surface temperature of the sun at its photosphere is about ______.

         37,000 K        
         5,800 K        
         1,000 K        
         1,000,000 K

Answer 8

5,800 K

Question 9

The fundamental nuclear reaction occurring in the core of the Sun is _________.

         nuclear fission        
         nuclear fusion of hydrogen into helium        
         nuclear fusion of helium to carbon        
         radioactive decay

Answer 9

nuclear fusion of hydrogen into helium

Question 10

The light radiated from the Sun’s surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about _________.

         three days ago        
         one hundred years ago        
         a few hundred thousand years ago        
         one thousand years ago

Answer 10

a few hundred thousand years ago

Question 11

What happens to energy in the Sun’s convection zone?

         Energy slowly leaks outward through the radiative diffusion of photons that repeatedly bounce off ions and electrons.        
         Energy is produced in the convection zone by nuclear fusion.        
         Energy is produced in the convection zone by thermal radiation.        
         Energy is transported outward by the rising of hot plasma and sinking of cooler plasma.

Answer 11

Energy is transported outward by the rising of hot plasma and sinking of cooler plasma.

Question 12

What do sunspots, solar prominences, and solar flares all have in common?

         They all have about the same temperature.        
         They all occur only in the Sun's photosphere.        
         They are all strongly influenced by magnetic fields on the Sun.        
         They are all shaped by the solar wind.

Answer 12

They are all strongly influenced by magnetic fields on the Sun.

Question 13

Which of the following is not a characteristic of the 11-year sunspot cycle?

         The Sun's entire magnetic field flip-flops with each cycle, so that the overall magnetic cycle averages 22 years.        
         The sunspot cycle is very steady, so that each 11-year cycle is nearly identical to every other 11-year cycle.        
         The likelihood of seeing solar prominences or solar flares is higher when sunspots are more common and lower when they are less common.        
         The number of sunspots on the Sun at any one time gradually rises and falls, with an average of 11 years between the times when sunspots are most numerous.

Answer 13

The sunspot cycle is very steady, so that each 11-year cycle is nearly identical to every other 11-year cycle.

Question 14

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

         The sunspot cycle is the cause of global warming.        
         The Sun's magnetic field, which plays a major role in the sunspot cycle, affects compass needles that we use on Earth.        
         Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.        
         The brightening and darkening of the Sun that occurs during the sunspot cycle affects plant photosynthesis here on Earth.        
         The sunspot cycle strongly influences Earth's weather.

Answer 14

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

Question 15

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.
Corna
chromosphere'
photosphere
convection zone
radiation zone
core

Answer 15

Corna
chromosphere'
photosphere
convection zone
radiation zone
core

Question 16

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

core
radiation zone
convection zone
photosphere
chromosphere
cornoa

Answer 16

core
radiation zone
convection zone
photosphere
chromosphere
cornoa

Question 17

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

core
radiation zone
convection zone
photosphere

Answer 17

core
radiation zone
convection zone
photosphere

Question 18

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

core
radiation zone
convection zone
photosphere

Answer 18

core
radiation zone
convection zone
photosphere

Question 19

In which of the following layer(s) of the Sun does nuclear fusion occur?
Select all that apply.

	corona
	radiation zone
	convection zone
	photosphere
	core
	chromosphere

Answer 19

core

Question 20

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.
Select all that apply.

	radiation zone
	convection zone
	chromosphere
	core
	corona
	photosphere

Answer 20

chromosphere
corona
photosphere

Question 21

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.

corona
chromosphere
photosphere

Answer 21

corona
chromosphere
photosphere

Question 22

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

photosphere
chromosphere
cornoa

Answer 22

photosphere
chromosphere
cornoa

Question 23

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

corona
chromosphere
photosphere

Answer 23

corona
chromosphere
photosphere

Question 24

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

corona
chromosphere
photosphere

Answer 24

corona
chromosphere
photosphere

Question 25

nuclear fusion of hydrogen in helium occurs in the

Answer 25

core

Question 26

Energy moves through the sun’s _____ by means of the rising of hot gas and falling of cooler gas.

Answer 26

Convection zone

Question 27

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

Answer 27

Photosphere

Question 28

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

Answer 28

Chromosphere

Question 29

We can see the Sun’s _____ most easily during total solar eclipses.

Answer 29

Corona

Question 30

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

Answer 30

radiation zone

Question 31

Which of the following changes would cause the fusion rate in the Sun’s core to increase?
Check all that apply.

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

Answer 31

An increase in the core temperature

A decrease in the core radius

Question 32

Which of the following must occur for a star’s core to reach equilibrium after an initial change in fusion rate?
Check all that apply.

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

Answer 32

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

Question 33

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

The Sun’s core would start to cool down and the rate of fusion would decrease.
The Sun’s core would reach a new equilibrium at a lower temperature.
The Sun’s core would reach a new equilibrium at a higher temperature.
The Sun’s core would start to heat up and the rate of fusion would increase even more.

Answer 33

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

Question 34

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. Observations

The photosphere is made mostly of hydrogen and helium
The photosphere emits ostly visible light.
The corona is hotter than the photosphere.
The sun emits neutrinos.
The sun generates energy by fusing hydrogen into helium in its core.
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 of the gas cloud that gave birth to our solar system.

Answer 34

The photosphere is made mostly of hydrogen and helium
The photosphere emits ostly visible light.
The corona is hotter than the photosphere.
The sun emits neutrinos.

Question 35

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. Inferences from a Model

The photosphere is made mostly of hydrogen and helium
The photosphere emits ostly visible light.
The corona is hotter than the photosphere.
The sun emits neutrinos.
The sun generates energy by fusing hydrogen into helium in its core.
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 of the gas cloud that gave birth to our solar system.

Answer 35

The sun generates energy by fusing hydrogen into helium in its core.
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 of the gas cloud that gave birth to our solar system.

Question 36

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?

The corona has a much lower gas density than the photosphere.
The corona emits much less total light than the photosphere.
The corona primarily emits X rays while the photosphere primarily emits visible light.
The corona is higher in the Sun’s atmosphere than the photosphere.

Answer 36

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

Question 37

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?

We infer the mass from a model of the Sun.
We first measure the Sun's size and density, then use these measurements to calculate the Sun’s mass.
We can calculate it by using the law of conservation of energy with the measured amount of light that the Sun emits.
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).

Answer 37

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).

Question 38

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?
Select all that apply.

Measurements of the varying number of sunspots on the Sun over time
Measurements of the Sun’s total energy output into space
Observations of neutrinos coming from the Sun
Observations of the total X-ray emission from the Sun’s corona
Measurement of the Sun’s mass

Answer 38

Measurements of the Sun’s total energy output into space

Observations of neutrinos coming from the Sun

Question 39

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. Solar Maximum

Occurs about 11 years after a solar maximum (on average)
Solar flares are most common
Auroras are most likely in Earth’s skies
Orbiting satellites are most at risk
Sunspots are most numerous on the Sun
Occurs about 5 to 6 years after a solar maximum ( on average)

Answer 39

Occurs about 11 years after a solar maximum (on average)
Solar flares are most common
Auroras are most likely in Earth's skies
Orbiting satellites are most at risk
Sunspots are most numerous on the Sun

Question 40

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. Solar Minimum

Occurs about 11 years after a solar maximum (on average)
Solar flares are most common
Auroras are most likely in Earth’s skies
Orbiting satellites are most at risk
Sunspots are most numerous on the Sun
Occurs about 5 to 6 years after a solar maximum ( on average)

Answer 40

Occurs about 5 to 6 years after a solar maximum ( on average)

Question 41

In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot due to gravitational contraction. What was the major drawback to this idea?

It predicted that Earth would also shrink in size with time, which would make it impossible to have stable geology on our planet.
It is physically impossible to generate heat simply by making a star shrink in size.
It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.
It predicted that the Sun would shrink noticeably as we watched it, but the Sun appears to be stable in size.

Answer 41

It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.

Question 42

What do we mean when we say that the Sun is in gravitational equilibrium?

The Sun maintains a steady temperature.
The Sun always has the same amount of mass, creating the same gravitational force.
The hydrogen gas in the Sun is balanced so that it never rises upward or falls downward.
There is a balance within the Sun between the outward push of pressure and the inward pull of gravity

Answer 42

There is a balance within the Sun between the outward push of pressure and the inward pull of gravity

Question 43

Which of the following correctly compares the Sun’s energy generation process to the energy generation process in human-built nuclear power plants?

Both processes involve nuclear fusion, but the Sun fuses hydrogen while nuclear power plants fuse uranium.
The Sun generates energy through nuclear reactions while nuclear power plants generate energy through chemical reactions.
The Sun generates energy through fission while nuclear power plants generate energy through fusion.
The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.

Answer 43

The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.

Question 44

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.
As the Sun was forming, nuclear fusion reactions in the shrinking clouds of gas slowly became stronger and stronger, until the Sun reached its current luminosity.
The Sun initially began generating energy through nuclear fusion as it formed, but today it generates energy primarily through the sunspot cycle.
The Sun initially began making energy through chemical reactions. These heated the interior enough to allow gravitational contraction and nuclear fusion to occur.

Answer 44

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.

Question 45

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
ejected into space in a solar wind
ejected into space by solar flares
reabsorbed as molecular hydrogen

Answer 45

converted to an amount of energy equal to 4 million tons times the speed of light squared

Question 46

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.
Nuclear fusion in the Sun's core produces visible light photons.
The visible light comes from energy level transitions as electrons in the Sun's hydrogen atoms jump between level 1 and level 2.
The Sun's gas is on fire like flames from wood or coal, and these flames emit visible light.

Answer 46

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.

Question 47

Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?

Nuclei are attracted to each other by the electromagnetic force, but this force is only strong enough to make nuclei stick when they are very close together.
Fusion can proceed only by the proton-proton chain, and therefore requires that protons come close enough together to be linked up into a chain.
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.
Nuclei have to be very hot in order to fuse, and the only way to get them hot is to bring them close together.

Answer 47

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.

Question 48

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.
They are extremely hot and emit all their radiation as X rays rather than visible light.
They are too cold to emit any visible light.
They are holes in the solar surface through which we can see through to deeper, darker layers of the Sun.

Answer 48

They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.

Question 49

How can we best observe the Sun’s chromosphere and corona?

The chromosphere is best observed with infrared telescopes and the corona is best observed with ultraviolet telescopes.
The chromosphere and corona are both best studied with visible light.
The chromosphere and corona are both best studied with radio telescopes.
The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.

Answer 49

The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.