Deck 14: Our Star

Question 1

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

A)It predicted that the Sun could last only about 25 million years,which is far less than the age of Earth.
B)It predicted that the Sun would shrink noticeably as we watched it,and the Sun appears to be stable in size.
C)It is physically impossible to generate heat simply by making a star shrink in size.
D)It predicted that Earth would also shrink,which would make it impossible to have stable geology on our planet.
E)It was proposed before Einstein's theory of general relativity and was therefore incorrect.

Answer 1

A

Question 2

How do human-built nuclear power plants on Earth generate energy?

A)chemical reactions
B)nuclear fusion
C)nuclear fission
D)converting kinetic energy into electricity
E)converting gravitational potential energy into electricity

Answer 2

C

Question 3

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

A)core,radiation zone,convection zone,corona,chromosphere,photosphere
B)core,corona,radiation zone,convection zone,photosphere,chromosphere
C)core,radiation zone,convection zone,photosphere,chromosphere,corona
D)core,convection zone,radiation zone,corona,chromosphere,photosphere
E)core,convection zone,radiation zone,photosphere,chromosphere,corona

Answer 3

C

Question 4

The core of the Sun is

A)at the same temperature and density as the surface.
B)at the same temperature but denser than the surface.
C)hotter and denser than the surface.
D)constantly rising to the surface through convection.
E)composed of iron.

Question 5

Which is closest to the temperature of the core of the Sun?

A)10,000 K
B)100,000 K
C)1 million K
D)10 million K
E)100 million K

Question 6

How does the Sun generate energy today?

A)nuclear fission
B)nuclear fusion
C)chemical reactions
D)gravitational contraction
E)gradually expanding in size

Question 7

At the center of the Sun,fusion converts hydrogen into

A)hydrogen compounds.
B)plasma.
C)radiation and elements like carbon and nitrogen.
D)radioactive elements like uranium and plutonium.
E)helium,energy,and neutrinos.

Question 8

Based on its surface temperature of 5,800 K,what color are most of the photons that leave the Sun's surface?

A)blue
B)red
C)yellow
D)orange
E)green

Question 9

Why do sunspots appear dark in pictures of the Sun?

A)They are too cold to emit any visible light.
B)They actually are fairly bright but appear dark against the even brighter background of the surrounding Sun.
C)They are holes in the solar surface through which we can see to deeper,darker layers of the Sun.
D)They are tiny black holes,absorbing all light that hits them.
E)They emit light in other wavelengths that we can't see.

Question 10

Which layer of the Sun do we normally see?

A)photosphere
B)corona
C)chromosphere
D)convection zone
E)radiation zone

Question 11

Sunspots are cooler than the surrounding solar surface because

A)they are regions where convection carries cooler material downward.
B)strong magnetic fields slow convection and prevent hot plasma from entering the region.
C)magnetic fields trap ionized gases that absorb light.
D)there is less fusion occurring there.
E)magnetic fields lift material from the surface of the Sun,cooling off the material faster.

Question 12

How much mass does the Sun lose through nuclear fusion per second?

A)4 tons
B)4 million tons
C)600 tons
D)600 million tons
E)Nothing: mass is conserved.

Question 13

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

A)The hydrogen gas in the Sun is balanced so that it never rises upward or falls downward.
B)The Sun maintains a steady temperature.
C)This is another way of stating that the Sun generates energy by nuclear fusion.
D)There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
E)The Sun always has the same amount of mass,creating the same gravitational force.

Question 14

When is/was gravitational contraction an important energy-generation mechanism for the Sun?

A)only during solar minimum
B)only during solar maximum
C)when the Sun was being formed from a collapsing cloud of gas
D)right after the Sun began fusing hydrogen in its core
E)when the Sun transports radiation through the convection zone

Question 15

Hydrogen fusion in the Sun requires a temperature (in Kelvin)of

A)thousands of degrees.
B)millions of degrees.
C)billions of degrees.
D)trillions of degrees.
E)any temperature,as long as gravity is strong enough.

Question 16

What two forces are balanced in what we call gravitational equilibrium?

A)the electromagnetic force and gravity
B)outward pressure and the strong force
C)outward pressure and inward gravity
D)the strong force and gravity
E)the strong force and kinetic energy

Question 17

What is the Sun made of?

A)100 percent hydrogen and helium
B)50 percent hydrogen,25 percent helium,25 percent other elements
C)70 percent helium,28 percent hydrogen,2 percent other elements
D)70 percent hydrogen,28 percent helium,2 percent other elements
E)98 percent hydrogen,2 percent helium and other elements

Question 18

What are the appropriate units for the Sun's luminosity?

A)watts
B)joules
C)meters
D)Newtons
E)kilograms

Question 19

The phase of matter in the Sun is

A)gas.
B)plasma.
C)liquid.
D)solid.
E)a mixture of all of the above

Question 20

What is the average temperature of the surface of the Sun?

A)1 million K
B)100,000 K
C)10,000 K
D)6,000 K
E)1,000 K

Question 21

What happens to energy in the convection zone of the Sun?

A)Energy slowly leaks outward through the diffusion of photons that repeatedly bounce off ions and electrons.
B)Energy is produced in the convection zone by nuclear fusion.
C)Energy is transported outward by the rising of hot plasma and the sinking of cooler plasma.
D)Energy is consumed in the convection zone by the creation of electrons and positrons.
E)Energy is conserved so while the gas moves up and down,there is no net transport of energy.

Question 22

Suppose that,for some unknown reason,the core of the Sun suddenly became hotter.Which of the following best describes what would happen?

A)Higher temperature would cause the rate of nuclear fusion to rise,which would increase the internal pressure,causing the core to expand and turn the Sun into a giant star.
B)Higher temperature would cause the rate of nuclear fusion to rise,which would increase the internal pressure,causing the core to expand and cool until the fusion rate returned to normal.
C)Higher temperature would cause the rate of fusion to fall,decreasing the internal pressure and causing the core to collapse until the rate of fusion returned to normal.
D)The higher temperature would not affect the fusion rate but would cause the core to expand and cool until the temperature returned to normal,with the core at a new,slightly larger size.

Question 23

Why must the Sun's rate of fusion gradually rise over billions of years?

A)The Sun becomes less efficient and must increase the rate of fusion to produce the same amount of energy.
B)Fusion reactions decrease the overall number of particles in the core,causing the core to shrink,converting gravitational potential energy into thermal energy,and increasing the rate of fusion.
C)The radiation produced by fusion reactions that is trapped in the core gradually raises the temperature,increasing the rate of fusion.
D)The Sun gets heavier as it gets older,and the stronger inward pull of gravity increases the fusion rate.
E)The rate of fusion is not rising;it is actually decreasing over time.

Question 24

What processes are involved in the sunspot cycle?

A)gravitational contraction of the Sun
B)wave motions in the solar interior
C)variations of the solar thermostat
D)the winding of magnetic field lines due to differential rotation
E)the interaction of the Earth's magnetic field with that of the Sun

Question 25

Suppose you put two protons near each other.Because of the electromagnetic force,the two protons will

A)collide.
B)remain stationary.
C)attract each other.
D)repel each other.
E)join together to form a nucleus.

Question 26

Why are neutrinos so difficult to detect?

A)because there are so rare
B)because they have no mass
C)because they move at nearly the speed of light
D)because they rarely interact with matter
E)because they are so small

Question 27

The first step in the proton-proton chain produces an antielectron,or positron.What happens to the positron?

A)It slowly works its way to the Sun's surface,where it escapes into space.
B)It rapidly escapes from the Sun,traveling into space at nearly the speed of light.
C)It is rapidly converted to energy when it meets an ordinary electron,resulting in matter-antimatter annihilation.
D)It quickly meets an ordinary electron,forming an electron-positron pair that remains stable.
E)It joins with a nearby neutron to form a proton.

Question 28

How do we know what goes on under the surface of the Sun?

A)We have X-ray images from satellites of the interior of the Sun.
B)Astronomers create mathematical models that use the laws of physics,the Sun's observed composition and mass,and computers to predict internal conditions.
C)We have sent probes below the surface of the Sun.
D)By measuring Doppler shifts,we observe vibrations of the Sun's surface that are created deep within the Sun.
E)both B and D

Question 29

Studies of sunquakes,or helioseismology,have revealed that

A)the Sun vibrates only on the surface.
B)"sunquakes" are caused by similar processes that create earthquakes on Earth.
C)the Sun generates energy by nuclear fusion.
D)our mathematical models of the solar interior are fairly accurate.
E)neutrinos from the solar core reach the solar surface easily.

Question 30

Which of the following statements about neutrinos is not true?

A)About a thousand trillion neutrinos are passing through your body every second.
B)Neutrinos are created as a by-product of the proton-proton chain.
C)Neutrinos have no electrical charge.
D)Neutrinos have a tendency to pass through just about anything without interactions,making them very difficult to detect.
E)The mass of a neutrino is 30 percent of the mass of an electron.

Question 31

The overall fusion reaction by which the Sun currently produces energy is

A)3 H ⇒ 1 Li + energy.
B)3 He ⇒ 1 C + energy.
C)4 H ⇒ 4 He + energy.
D)6 H ⇒ 1 He + energy.
E)4 H ⇒ 1 He + energy.

Question 32

What observations characterize solar maximum?

A)The Sun becomes much brighter.
B)The Sun emits light of longer average wavelength.
C)The Sun rotates faster at the equator.
D)We see many sunspots on the surface of the Sun.
E)all of the above

Question 33

Which is the strongest of the fundamental forces in the universe?

A)strong force
B)weak force
C)electromagnetic force
D)gravitational force
E)none of the above

Question 34

Which of the following statements about the sunspot cycle is not true?

A)The number of sunspots peaks approximately every 11 years.
B)With each subsequent peak in the number of sunspots,the magnetic polarity of the Sun is the reverse of the previous peak.
C)The rate of nuclear fusion in the Sun peaks about every 11 years.
D)The cycle is truly a cycle of magnetic activity,and variations in the number of sunspots are only one manifestation of the cycle.
E)The number of solar flares peaks about every 11 years.

Question 35

Most of the energy produced in the Sun is released in the form of visible light from the photosphere.However,some energy is released from the upper layers of the solar atmosphere.Which of the following best describes where other forms of light are released?

A)The chromosphere is the source of ultraviolet light,and the corona is the source of X-rays.
B)The chromosphere is the source of infrared light,and the corona is the source of ultraviolet light.
C)The chromosphere is the source of X-rays,and the corona is the source of radio waves.
D)The convection zone is the source of ultraviolet light,and the upper photosphere is the source of X-rays.
E)Radio waves can pass directly through the gas which allows us to see the core.

Question 36

What is the solution to the solar neutrino problem?

A)The Sun is generating energy other than by nuclear fusion.
B)The Sun is generating much less energy than we think it is.
C)We do not know how to detect electron neutrinos.
D)Not all fusion reactions create electron neutrinos.
E)The electron neutrinos created in the Sun change into another type of neutrino that we could not detect with our original equipment.

Question 37

What is granulation in the Sun?

A)the bubbling pattern on the photosphere produced by the underlying convection
B)another name for the way sunspots look on the surface of the Sun
C)elements in the Sun other than hydrogen and helium
D)dust particles in the Sun that haven't been turned into plasma
E)lumps of denser material in the Sun

Question 38

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

A)a hundred years ago.
B)a thousand years ago.
C)tens of thousands of years ago.
D)hundreds of thousands of years ago.
E)a million years ago.

Question 39

What are coronal holes?

A)regions on the photosphere where magnetic lines poke through,creating the cooler areas of the sunspots
B)areas of the corona where magnetic field lines project into space,allowing charged particles to escape the Sun,becoming part of the solar wind
C)holes in the corona of the Sun that allow us to see the photosphere
D)tunnels in the outer layers of the Sun through which photons can escape more quickly than through the radiation zone
E)all of the above

Question 40

Which statement best describes the solar neutrino problem?

A)Theoretical models predict that neutrinos should be produced in the Sun,but no neutrinos have ever been observed to be coming from the Sun.
B)Solar neutrinos were detected but in fewer numbers than predicted by theoretical models.
C)No one understands how it can be possible for neutrinos to be produced in the Sun.
D)Our current understanding of fusion in the Sun suggests that all neutrinos should be destroyed before they arrive at Earth,yet neutrinos are being detected.
E)The term solar neutrino problem refers to the fact that neutrinos are extremely difficult to detect.

Question 41

Nuclear power plants on Earth create energy in the same way as the Sun.

Question 42

The solar neutrino problem was solved when we realized neutrinos change types when they pass through matter.

Question 43

Newer neutrino detectors have confirmed the total number of solar neutrinos does in fact match predictions.

Question 44

Although the Sun does not generate energy by gravitational contraction today,this energy-generation mechanism was important when the Sun was forming.

Question 45

The chromosphere is the layer of the Sun that we see as its visible surface.

Question 46

Humans have not sent a spacecraft into the interior of the Sun to confirm any models of the interior.What evidence then do we have to support our current ideas about the solar interior?

A)solar neutrinos
B)solar flares
C)sun spots
D)X-ray observations that penetrate the gas
E)We have no evidence,just informed guesses.

Question 47

Energy from the core of the Sun first travels slowly through the convection zone and then much faster through the radiation zone.

Question 48

What is the solar thermostat?

Question 49

Gravitational equilibrium means that the surface and the core of the Sun are at the same pressure.

Question 50

The Sun is a relatively young star,near the beginning of its life.

Question 51

Sunspots are cooler than the surrounding region of the Sun's surface.

Question 52

The proton-proton chain converts four hydrogen nuclei into one helium nucleus.

Question 53

Describe some of the early theories for why the Sun shines and why they are no longer accepted as viable.

Question 54

The corona and chromosphere are hotter than the photosphere.

Question 55

Briefly explain how the Sun became hot enough for nuclear fusion.

Question 56

The Sun is a ball of gas that is on fire.

Question 57

The core of the Sun is at a temperature of about 20,000 K.

Question 58

The Sun generates energy primarily by nuclear fission.

Question 59

Briefly describe why the fact that we detect neutrinos coming from the Sun supports the idea that the Sun generates energy by nuclear fusion.

Question 60

The Sun's rate of fusion is gradually increasing over time.

Question 61

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

A)the strong force and the weak force
B)the inward pull of gravity and outward pressure
C)the inward pull of gravity and surface tension
D)the strong force and the electromagnetic force

Question 62

Process of Science: Explain the reasoning that led to our understanding of nuclear energy being the source of the Sun's light.

Question 63

The Sun will exhaust its nuclear fuel in about

A)5000 AD.
B)5 million years.
C)5 billion years.
D)50 billion years.

Question 64

The source of energy that keeps the Sun shining today is

A)nuclear fission.
B)gravitational contraction.
C)chemical reactions.
D)nuclear fusion.

Question 65

Briefly explain why sunspots are cooler than surrounding regions of the Sun and why they look dark in photos.

Question 66

Process of Science: How do we know what is going on in the center of the Sun so well if we cannot see it or send spacecraft to it?

Question 67

Might changes in the Sun affect weather or climate on Earth?

Question 68

The Sun's surface,as we see it with our eyes,is called the

A)chromosphere.
B)photosphere.
C)corona.
D)core.

Question 69

Describe two general ways we learn about the Sun's interior.

Question 70

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

A)4 billion years
B)25 million years
C)10,000 years
D)400 million years

Question 71

When we say that the Sun is a ball of plasma,we mean that

A)the Sun is made of material that acts like a liquid acts on Earth.
B)the Sun is made of atoms and molecules.
C)the Sun consists of gas in which many or most of the atoms are ionized (missing electrons).
D)the Sun is roughly the same color as blood.

Question 72

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

A)Gravitational contraction involves nuclear fusion,which generates a lot of heat.
B)When a star contracts in size,gravitational potential energy is converted to thermal energy.
C)Heat is generated when gravity contracts,because gravity is an inverse square law force.
D)Gravitational contraction involves the generation of heat by chemical reactions,much like the burning of coal.

Question 73

Process of Science: Why is it important to understand the Sun in order to understand the Earth's radiation belts and space weather?

Question 74

What are the appropriate units for the Sun's luminosity?

A)watts
B)joules
C)Newtons
D)kilograms

Question 75

Briefly describe the phenomena of the sunspot cycle.

Question 76

What is the Sun made of (by mass)?

A)70% hydrogen,28% helium,2% other elements
B)100% hydrogen and helium
C)50% hydrogen,25% helium,25% other elements
D)90% dark matter,10% ordinary matter

Question 77

Imagine you are plunging into the Sun,starting from Earth.Briefly describe what you will see as you descend.

Question 78

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

A)core,radiation zone,convection zone,corona,chromosphere,photosphere
B)core,convection zone,radiation zone,corona,chromosphere,photosphere
C)core,radiation zone,convection zone,photosphere,chromosphere,corona
D)core,corona,radiation zone,convection zone,photosphere,chromosphere

Question 79

List at least two ways the sunspot cycle affects us on Earth.

Question 80

What is the solar neutrino problem?