Deck 10: Our Star

Question 1

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

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

Answer 1

A

Question 2

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

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

Answer 2

D

Question 3

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

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

Answer 3

A

Question 4

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) Microwave
B) Infrared
C) Visible
D) Ultraviolet
E) X-ray

Question 5

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-energy is conserved.

Question 6

Suppose you try to bring two protons close together. Because of the electromagnetic force, the two protons will

A) collide.
B) remain stationary.
C) attract one another.
D) repel one another.
E) join together to form a deuterium nucleus.

Question 7

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

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

Question 8

Imagine that you are trying to stop neutrinos with a lead shield. How thick would you need to make this shield to ensure that it can stop a neutrino?

A) About one meter.
B) About 700,000 kilometers (the radius of the Sun).
C) About 150 million kilometers (the size of an astronomical unit).
D) About one light year.
E) About 14 billion light years (the size of the observable universe).

Question 9

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 10

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 did not know how to detect neutrinos.
D) Not all fusion reactions create neutrinos.
E) The electron neutrinos created in the Sun's core change into another type of neutrino that we did not detect.

Question 11

The core of the Sun is

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

Question 12

By what process does the Sun generate energy?

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

Question 13

Sunspots are cooler than the surrounding gas in the photosphere 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 sunspot and quickly cool the material.

Question 14

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

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

Question 15

At the center of the Sun, nuclear fusion converts hydrogen into

A) hydrogen compounds such as methane.
B) molecular hydrogen.
C) radiation and elements such as carbon and nitrogen.
D) radioactive elements such as uranium and plutonium.
E) helium, gamma rays, and neutrinos.

Question 16

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) Building mathematical models that use the laws of physics.
C) Detecting solar neutrinos generated in the Sun's core.
D) Measuring Doppler shifts to observe solar vibrations.
E) both C and D

Question 17

What are coronal holes?

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

Question 18

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

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

Question 19

Studies of solar vibrations have revealed that

A) the Sun vibrates only on the surface.
B) they are caused by processes similar to those that create earthquakes.
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 20

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

Question 21

Briefly describe why the detection of neutrinos coming from the Sun supports the theory that the Sun generates energy by nuclear fusion.

Question 22

The Sun generates energy primarily by nuclear fission.

Question 23

Interdisciplinary Science: Significant advancements in science often occur when several separate and distinct scientific disciplines come together to address a single question. Use the search for the Sun's energy source as a case study. Outline how astronomy and physics were driven to consider new possibilities for the Sun's energy by the fields of geology and biology.

Question 24

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

Question 25

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 its poles.
D) There are many sunspots visible on the surface of the Sun.
E) all of the above

Question 26

Nuclear Fusion Power Plants: The public often reacts with fear to any energy source involving the word "nuclear." Imagine that you are discussion the problem of energy generation with a friend, and you mention that nuclear fusion power plants should be investigated. Your friend expresses worry about all of the nuclear waste that would be produced. How would you explain to your friend that this fear is misplaced?

Question 27

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

Question 28

Basis for Fundamental Solar Data: Table 10.1 in your text lists all of the basic fundamental data for the Sun: its mass, radius, luminosity, rotation rate, surface temperature, and composition. Taking each of the quantities in turn, outline the basic observations and physical principles used to infer the values. When done, consider one final fact about the Sun: its core temperature is about 15 million degrees (Kelvin). What observations support this value? Do you consider the Sun's core temperature to be more or less well established than the basic data of Table 10.1? Explain.

Question 29

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

Question 30

What was the solar neutrino problem?

Question 31

What is the solar thermostat?

Question 32

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

Question 33

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

Question 34

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

Question 35

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

Question 36

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

Question 37

The corona and chromosphere are hotter than the photosphere.

Question 38

Describe some of the early theories for the Sun's energy source and why they are no longer accepted as viable.

Question 39

The temperature of the Sun's core is about 20,000 K.

Question 40

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

Question 41

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

A) When a star contracts in size, gravitational potential energy is converted to thermal energy.
B) Gravitational contraction involves nuclear fusion, which generates a lot of heat.
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 42

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

Question 43

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

A) Photosphere, convection zone, core, radiation zone
B) Core, radiation zone, convection zone, photosphere
C) Radiation zone, core, convection zone, photosphere
D) Photosphere, convection zone, radiation zone, core

Question 44

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

Question 45

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

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

Question 46

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

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

Question 47

Briefly describe the Sun's 22 year activity cycle.

Question 48

How do we know how old the Sun is?

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

Question 49

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

A) Sending a probe to the Sun to plunge into its interior
B) Monitoring the helium content of the surface of the Sun
C) Taking movies of the solar prominences and flares
D) Comparing model predictions to how the Sun actually vibrates

Question 50

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

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

Question 51

Where in the Sun do fusion reactions happen?

A) Core and radiation zone
B) Everywhere inside the Sun
C) Only the core

Question 52

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

Question 53

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 has lived for billions of years
C) Because the Sun is solid
D) Because gas pressure balances gravity in the Sun

Question 54

Which weighs more?

A) They both weigh exactly the same.
B) Four protons
C) Two neutrons and two protons in a helium nucleus

Question 55

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

A) 4 ¹/₂ billion years
B) 25 million years
C) 10,000 years
D) 400 million years

Question 56

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 57

Imagine you are plunging into the Sun, starting from Earth. Briefly describe what you will experience on your journey.

Question 58

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

A) The fusion rate decreases, then the core shrinks and heats.
B) The fusion rate decreases, then the core expands 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 59

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

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

Question 60

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

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

Question 61

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

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

Question 62

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 63

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) Gravitational force and outward pressure
C) Gravitational force and surface tension
D) The strong force and the electromagnetic force

Question 64

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

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

Question 65

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

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

Question 66

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

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

Question 67

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

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

Question 68

The proton-proton chain is ________.

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

Question 69

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 70

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

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

Question 71

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

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

Question 72

The overall result of the proton-proton chain is:

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

Question 73

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

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

Question 74

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) few hundred thousand years ago
B) three days ago
C) one hundred years ago
D) one thousand years ago

Question 75

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

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

Question 76

What is the solar wind?

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

Question 77

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 have about the same temperature.
C) They are all shaped by the solar wind.
D) They all occur only in the Sun's photosphere.

Question 78

Why are neutrinos so difficult to detect?

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

Question 79

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

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

Question 80

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

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