Deck 11: Our Star

Question 1

If the sun's surface cooled, how would its appearance change?

A)It would appear more blue.
B)It would appear more red.
C)It would stay the same.
D)It would become bright white.

Answer 1

B

Question 2

Why isn't the Sun shrinking or expanding?

A)Because the Sun is spinning so fast, the centrifugal forces keep the surface of the Sun supported against collapse.
B)because the Sun is solid
C)because gas pressure balances gravity in the Sun
D)because the Sun has lived for billions of years

Answer 2

C

Question 3

All but one of the following statements describe why scientists doubt the solar sunspot cycle affects global climate. Identify which statement is irrelevant to the explanation.

A)Solar winds can affect satellite communications.
B)Variations in solar activity affect the Sun's luminosity by a very tiny amount.
C)The solar cycle varies every 11 years; average Earth temperatures do not show an 11 year variation.
D)The variations in solar particle winds do not change the temperature of the Earth's ocean or ground.

Answer 3

A

Question 4

What are coronal holes?

A)areas in the corona that allow us to see through to the photosphere
B)regions in the photosphere where magnetic lines gather, creating cooler areas with much less plasma
C)tunnels in the outer layers of the Sun that allow photons to escape and form the solar wind
D)areas of the corona where magnetic field lines project out into space, allowing charged particles to escape and form the solar wind
E)all of the above

Question 5

What would happen in the Sun if the temperature of the core decreased?

A)The fusion rate decreases, then the core expands and heats.
B)The fusion rate decreases, then the core shrinks and heats.
C)The fusion rate increases, then the core expands and cools.
D)The fusion rate increases, then the core shrinks and heats.

Question 6

By what process does the Sun generate energy?

A)nuclear fission
B)nuclear fusion
C)chemical reactions
D)gradual expansion
E)gravitational contraction

Question 7

Based on its surface temperature of 6,000 K, most photons that leave the Sun's surface lie in which region of the electromagnetic spectrum?

A)ultraviolet
B)microwave
C)X- ray
D)visible
E)infrared

Question 8

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

A)gravitational force and surface tension
B)gravitational force and outward pressure
C)the strong force and the electromagnetic force
D)the strong force and the weak force

Question 9

Approximately how many neutrinos pass through your body each second?

A)about 1023
B)about one thousand
C)about a thousand trillion
D)None; they are blocked by the Earth's atmosphere.

Question 10

Where in the Sun do fusion reactions happen?

A)only the core
B)everywhere inside the Sun
C)core and radiation zone

Question 11

A computer accessory 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?

A)Solar neutrinos are generated by solar winds, but we're in a solar minimum now, so the risk of damage is very low.
B)Neutrinos rarely, if ever, interact with your computer.
C)There's no such thing as a solar neutrino.
D)The Earth's natural magnetic field already offers excellent protection against the onslaught of solar neutrinos.

Question 12

The Sun's average surface (photosphere)temperature is about .

A)1,000 K
B)37,000 K
C)1,000,000 K
D)5,800 K

Question 13

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 .

A)reabsorbed as molecular hydrogen
B)ejected into space by solar flares
C)converted to an amount of energy equal to 4 million tons times the speed of light squared
D)ejected into space in a solar wind

Question 14

Why do sunspots appear dark?

A)They are thick clouds on the sun, blocking its light.
B)They are regions nearly devoid of gas.
C)They are composed of different elements than the rest of the sun.
D)They are regions that are significantly cooler than the rest of the photosphere.

Question 15

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

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

Question 16

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

A)4 tons
B)600 tons
C)4 million tons
D)600 million tons
E)Nothing; mass- energy is conserved.

Question 17

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

A)monitor changes in Earth's atmosphere
B)use computer models to predict interior conditions
C)send probes to measure the temperature
D)use hot gas to create a small Sun in a laboratory

Question 18

It takes years for the sun to progress through one sunspot cycle, wherein sunspots appear at high latitudes, shift to lower and lower latitude, then return to high latitudes. Refer to the graph above.

A)about 10 years
B)about 110 years
C)about 1 year
D)This figure cannot be used to answer this question.

Question 19

The core of the Sun is

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

Question 20

Order the interior layers of the Sun from the hottest to the coldest.

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

Question 21

Which has a greater mass?

A)two neutrons and two protons in a helium nucleus
B)four protons
C)A and B both have exactly the same mass.

Question 22

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

A)radioactive decay
B)nuclear fission
C)nuclear fusion of hydrogen into helium
D)nuclear fusion of helium into carbon

Question 23

Which of the following is the phase of matter in the Sun?

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

Question 24

If the Sun's core suddenly shrank a little bit, what would happen in the Sun?

A)The core would heat up, causing it to radiate so much energy that it would shrink even more.
B)The core would heat up, fusion rates would increase, the core would re- expand.
C)The core would cool off and continue to shrink as its density increased.
D)The density of the core would decrease, causing the core to cool off and expand.

Question 25

According to this Doppler map of the sun's surface, about how fast is the sun rotating around at its equator?

A)about 20,000 m/s
B)about 2000 m/s
C)about 200 m/s
D)It is not rotating.

Question 26

Which of the following is not a method astronomers use to determine the physical conditions inside the Sun?

A)observing X- ray images of the solar interior using satellites
B)measuring Doppler shifts to observe solar vibrations
C)building mathematical models that use the laws of physics
D)detecting solar neutrinos generated in the Sun's core
E)both C and D

Question 27

What is the solar wind?

A)the wind that causes huge arcs of gas to rise above the Sun's surface
B)the strong wind that blows sunspots around on the surface of the Sun
C)the uppermost layer of the Sun, lying just above the corona
D)a stream of charged particles flowing outward from the surface of the Sun

Question 28

Which of the following best describes why the Sun emits most of its energy in the form of visible light?

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

Question 29

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

A)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.
B)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.
C)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.
D)Nuclei have to be very hot in order to fuse, and the only way to get them hot is to bring them close together.

Question 30

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

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

Question 31

Satellites in low- Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because .

A)of increased magnetic interference
B)they are more likely to have their electronics "fried" by a solar flare during solar maximum
C)Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits
D)it is too dangerous to send the Space Shuttle to service satellites during solar maximum

Question 32

How do we test our computer models for the interior of the Sun?

A)monitoring the helium content of the surface of the Sun
B)comparing model predictions to how the Sun actually vibrates
C)taking movies of the solar prominences and flares
D)sending a probe to the Sun to plunge into its interior

Question 33

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

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

Question 34

Which of the following is the best answer to the question, "Why does the Sun shine?"

A)As the Sun was forming, gravitational contraction increased the Sun's temperature until the core became hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.
B)The Sun initially began generating energy through nuclear fusion as it formed, but today it generates energy primarily through the sunspot cycle.
C)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.
D)The Sun initially began making energy through chemical reactions. These heated the interior enough to allow gravitational contraction and nuclear fusion to occur.

Question 35

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

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

Question 36

How does the Sun's mass compare to Earth's mass?

A)The Sun's mass is about 30 times the mass of the Earth.
B)The Sun's mass is about 300,000 times the mass of the Earth.
C)The Sun's mass is about 300 times the mass of the Earth.
D)Both have approximately the same mass.

Question 37

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

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

Question 38

Which of the following statements about the Sun is an inference from a model, not an observation?

A)The convection zone is cooler than the radiation zone.
B)The photosphere emits visible light.
C)The corona is hotter than the photosphere.
D)The Sun emits neutrinos.

Question 39

At the time the hypothesis was suggested, what major problem was identified with the idea that the Sun was powered by gravitational contraction?

A)This process could not possibly lead to the observed power output of the Sun.
B)Contracting objects cool down rather than heat up.
C)19th century astronomers should have been able to measure the required change in the Sun's size.
D)This process would power the Sun for only about 25 million years, but geologists already had evidence the Earth was much older than that.

Question 40

When the temperature of the Sun's core goes down, what happens next?

A)Fusion reactions slow down; the core expands and heats.
B)Fusion reactions speed up; the core shrinks and cools.
C)Fusion reactions slow down; the core shrinks and heats.
D)Fusion reactions speed up; the core expands and cools.

Question 41

The proton- proton chain is _ .

A)another name for the force that holds protons together in atomic nuclei
B)the specific set of nuclear reactions through which the Sun fuses hydrogen into helium
C)an alternative way of generating energy that is different from the fusion of hydrogen into helium
D)the linkage of numerous protons into long chains

Question 42

Which of the following quantities is equal to the energy per second generated by the Sun's nuclear reactions?

A)the temperature at the Sun's photosphere
B)the luminosity of the Sun's photosphere
C)the force of gravity holding the Sun together
D)the temperature of the Sun's core

Question 43

The Sun will exhaust its nuclear fuel in about .

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

Question 44

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

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

Question 45

Which of the following processes is involved in the sunspot cycle?

A)an imbalance in the operation of the solar thermostat
B)small variations in the rate of nuclear energy generation in the solar interior
C)a large change in the amount of visible light emitted by the Sun
D)a slight gravitational contraction of the Sun
E)the winding of magnetic field lines due to the Sun's rotation

Question 46

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

A)Kilograms
B)Joules
C)Watts
D)Newtons

Question 47

Why do sunspots appear dark in pictures of the Sun?

A)They are holes in the solar surface through which we can see through to deeper, darker layers of the Sun.
B)They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.
C)They are too cold to emit any visible light.
D)They are extremely hot and emit all their radiation as X- rays rather than visible light.

Question 48

What observations characterize solar maximum?

A)There are many sunspots visible on the surface of the Sun.
B)The Sun emits light of longer average wavelength.
C)The Sun rotates faster at its poles.
D)The Sun becomes much brighter.
E)all of the above

Question 49

Studies of solar vibrations have revealed that

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

Question 50

It takes years for the sun to progress through one sunspot cycle from a maximum area covered with sunspots, to a minimum, and back to a maximum. Refer to the graph above.

A)about 1 year
B)about 110 years
C)about 10 years
D)This figure cannot be used to answer this question.

Question 51

Why are neutrinos so difficult to detect?

A)They have no mass.
B)They are extremely rare.
C)They have a tendency to pass through just about any material without any interactions.
D)No one knows; this is the essence of the "solar neutrino problem."

Question 52

The Sun's surface seethes and churns with a bubbling pattern. Why?

A)The Sun's surface is boiling.
B)The churning is an illusion created by varying radiation, as the gas on the Sun's surface is actually quite still.
C)We are seeing hot gas rising and cool gas falling due to the convection that occurs beneath the surface.
D)The churning gas is being stirred up by the strong solar wind.

Question 53

By what process do nuclear power plants on the Earth generate energy?

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

Question 54

How can we measure the strength of magnetic fields on the Sun?

A)by observing auroras here on Earth
B)by looking for the splitting of spectral lines in the Sun's spectrum
C)by observing the sizes of sunspots: Bigger sunspots mean a stronger field
D)only by using sophisticated computer models because there are no observational ways of measuring magnetic field strength

Question 55

Energy balance in the Sun refers to a balance between .

A)the amount of energy the Sun radiates into space and the amount of energy that reaches Earth
B)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
C)the force of gravity pulling inward and the force due to pressure pushing outward
D)the mass that the Sun loses each second and the amount of mass converted into energy each second

Question 56

Which of the following choices is not a way by which we can study the inside of the Sun?

A)We can make a computer model of the Sun's interior that allows us to predict the observable properties of the Sun.
B)We can send a space probe into the Sun's photosphere.
C)We can study solar neutrinos.
D)We can probe the interior of the Sun by studying the vibrations in its photosphere.

Question 57

If the Sun suddenly stopped emitting neutrinos, what might we infer (after checking that our neutrino detectors were still operational)?

A)Fusion reactions in the Sun ceased a few hundred thousand years ago.
B)The Sun has exhausted its supply of neutrinos.
C)Fission reactions in the Sun have ceased.
D)Fusion reactions in the Sun have ceased.

Question 58

Sunspots are cooler than the surrounding gas in the photosphere because

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

Question 59

What is shown by the small- scale changes in the shading in the figure above?

A)variations in the height of the solar surface
B)variations in the temperature of the photosphere
C)vibrations seen at the solar surface
D)Nothing; this is an artist's rendering of the sun.

Question 60

Which of the following statements is an inference from a model (rather than an observation)?

A)The Sun emits neutrinos.
B)The photosphere emits visible light.
C)The photosphere is made out of mainly hydrogen and helium.
D)The corona is hotter than the photosphere.
E)The Sun's core is gradually turning hydrogen into helium.

Question 61

The star Alpha Centauri A is the same type of star as the Sun, but its luminosity is about 1.6 times that of the Sun. What can we conclude?

A)Alpha Centauri A is much farther from Earth than the Sun.
B)Alpha Centauri A fuses hydrogen into helium in its core at a higher rate than our Sun.
C)Alpha Centauri A must have a vastly different interior structure than the Sun.
D)Alpha Centauri A has a much higher surface temperature than the Sun.

Question 62

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

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

Question 63

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

A)The Sun's core would cool and the rate of fusion would decrease.
B)The Sun's core would reach a new equilibrium, but at a higher temperature.
C)The Sun's core would heat and the rate of fusion would increase further.
D)The Sun's core would reach a new equilibrium, but at a cooler temperature.

Question 64

How do we know how old the Sun is?

A)from Newton's version of Kepler's third law and the orbits of the planets
B)from ages of solar system meteorites, based on radioactive elements
C)from calculating its fuel supply and how fast it is using it up
D)from its speed and distance from us

Question 65

The light radiated from the Sun's surface reaches Earth in about 8 minutes. However, the energy of this light was released by fusion in the Sun's core about

A)several hundred thousand years ago.
B)8 minutes ago.
C)several thousand years ago.
D)several hundred years ago.
E)11 years ago.

Question 66

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

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

Question 67

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

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

Question 68

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

A)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.
B)The sunspot cycle is very steady, so that each 11- year cycle is nearly identical to every other 11- year cycle.
C)The Sun's entire magnetic field flip- flops with each cycle, so that the overall magnetic cycle averages 22 years.
D)The likelihood of seeing solar prominences or solar flares is higher when sunspots are more common and lower when they are less common.

Question 69

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?

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

Question 70

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

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

Question 71

Why does the Sun emit neutrinos?

A)Fusion in the Sun's core creates neutrinos.
B)The Sun was born with a supply of neutrinos that it gradually emits into space.
C)Solar flares create neutrinos with magnetic fields.
D)Convection releases neutrinos, which random walk through the radiation zone.
E)The Sun does not emit neutrinos.

Question 72

The overall result of the proton- proton chain is .

A)6 H becomes 1 He + energy
B)4 H becomes 1 He + energy
C)p + p becomes 2H + energy
D)individual protons are joined into long chains of protons

Question 73

What would happen to the core of the sun if its temperature rose slightly?

A)The rate at which fusion occurs would decrease, leading to a contraction of the core, which would in turn cause a further temperature rise.
B)The rate at which fusion occurs would increase, leading to an expansion of the core, which would in turn cause the temperature to drop back down.
C)The rate at which fusion occurs would increase, leading to a contraction of the core, which would in turn cause the temperature to rise even further.
D)The rate at which fusion occurs would decrease, leading to an expansion of the core, which would in turn cause the temperature to drop back down.

Question 74

What keeps the Sun's outer layers from continuing to fall inward in a gravitational collapse?

A)outward pressure due to super- heated gas
B)electromagnetic repulsion between protons
C)the strong force between protons
D)neutrinos produced by nuclear fusion drag gas outward

Question 75

The intricate patterns visible in an X- ray image of the Sun generally show _ .

A)structure within sunspots
B)extremely hot plasma flowing along magnetic field lines
C)helioseismological fluctuations
D)a bubbling pattern on the photosphere

Question 76

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

A)The magnetic polarity of the Sun reverses approximately every 11 years.
B)The rate of nuclear fusion in the Sun peaks about every 11 years.
C)At solar minimum, the first sunspots form at mid- latitudes on the Sun.
D)The number of solar flares peaks about every 11 years.
E)The number of sunspots peaks approximately every 11 years.

Question 77

What is the Sun made of (by mass)?

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

Question 78

What is the only force that can overcome the repulsion between two positively charged nuclei to bind them into an atomic nucleus?

A)the Coriolis force
B)the electromagnetic force
C)the strong force
D)the gravitational force
E)the weak force

Question 79

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

A)4)5 billion years
B)400 million years
C)25 million years
D)10,000 years

Question 80

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

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