Deck 14: Our Starthe Sun

Question 1

The fact that the surface of the Sun rings like a bell lets us understand its interior better.

Answer 1

True

Question 2

In the radiative zone inside the Sun, photons are transported from the core to the convective zone in a matter of seconds.

Answer 2

False

Question 3

In our Sun, hydrostatic equilibrium exists only in the core, where energy production via fusion can balance gravity.

Answer 3

False

Question 4

If the Sun stopped nuclear fusion in its core, it would take 1,000 years for its luminosity to change.

Question 5

Our Sun is unique compared to the other stars in our galaxy because of its:

A) temperature
B) size
C) evolutionary stage
D) proximity
E) mass

Question 6

Which of the following curves best matches the shape of a graph of the density of material inside the Sun (in thousands of kg/m³) as you move further away from the center?

A) A
B) B
C) C
D) D
E) E

Question 7

The Sun has a mass of:

A) 2 * 10¹⁰ kg
B) 2 * 10²⁵ kg
C) 2 * 10³⁰ kg
D) 2 *10³⁵ kg
E) 2 * 10⁴⁵ kg

Question 8

The solar neutrino problem was solved by postulating that neutrinos have a small mass and oscillate between three different types of neutrino.

Question 9

Neutrinos are particles with small masses that interact easily with normal matter.

Question 10

Density, temperature, and pressure increase as you move inward in the interior of the Sun. This means that the force of gravity, (Fg = GMm/r²), _________ as you move inward toward the core.

A) increases
B) decreases
C) stays the same
D) There is not enough information to answer.

Question 11

Hydrostatic equilibrium is a balance between:

A) heat and centrifugal force
B) core temperature and surface temperature
C) pressure and gravity
D) radiation and heat
E) centrifugal force and gravity

Question 12

If coronal holes covered a larger fraction of the Sun's surface, the solar wind would contain a higher density of particles.

Question 13

Which force is responsible for holding the protons and neutrons in the nucleus of an atom together?

A) gravity
B) strong nuclear force
C) electric force
D) magnetic force
E) Electrons push them together.

Question 14

Nuclei of atoms are held together by gravity.

Question 15

The solar magnetic field switches polarity every 11 years.

Question 16

The balance of energy in the solar interior means that:

A) energy production rate in the core equals the rate of radiation escaping the Sun's surface
B) the source of energy in the core is stable and will sustain the Sun for millions of years
C) the outer layers of the Sun absorb and re-emit the radiation from the core at increasingly longer wavelengths
D) radiation pressure balances the weight of the overlying solar layers
E) the core of the Sun has higher pressure than the outer layers

Question 17

The net result of the proton-proton chain of nuclear reactions is that four protons are converted into one helium nucleus and energy, electrons, and neutrinos are released.

Question 18

The temperature of the corona is much hotter than any other layer in the solar atmosphere.

Question 19

At the center of the Sun, the temperature is roughly 15 million K.

Question 20

In a sunspot, the umbra is cooler than the penumbra.

Question 21

Why is hydrogen burning the main energy source for main-sequence stars?

A) Hydrogen is the most common element in stars.
B) Hydrogen nuclei have the smallest positive charge.
C) Hydrogen burning is the most efficient of all fusion or fission reactions.
D) Hydrogen can fuse at temperatures lower than other elements.
E) All the above are valid reasons.

Question 22

The interior zones of the Sun are distinguished by:

A) jumps in density between zones
B) their temperature profiles
C) pressure differences inside each zone
D) their modes of energy transport
E) all of the above

Question 23

Light from the Sun's photosphere reaches Earth approximately _________ times faster than photons released in fusion in the core.

A) 1,000
B) 600,000
C) 1 million
D) 6 billion
E) 10 billion

Question 24

If the Sun converts 5 * 10¹¹ kg of H to He per second and the mass of a single hydrogen nucleus is 1.7 *10^-27 kg, how many net proton-proton reactions go on per second in the Sun? What is the luminosity produced if the mass difference between a single helium nucleus and four hydrogen nuclei is 4 *10^-29 kg? Note that 1 Watt * 1 m² kg/s³.

A) 7 *10³⁷ reactions per sec; 3 * 10²⁶ Watt
B) 3*10³⁸ reactions per sec; 10²⁷ Watt
C) 3 * 10³⁸ reactions per sec; 4 * 10²⁶ Watt
D) 7 *10³⁷ reactions per sec; 5 * 10²⁵ Watt
E) 3 * 10³⁷ reactions per sec; 6* 10²⁴ Watt

Question 25

Some restaurants place food under infrared heat lamps so that it stays warm after it has been cooked. This is an example of energy being transported by:

A) radiation
B) convection
C) conduction
D) convection and conduction
E) radiation and conduction

Question 26

Approximately how long does it take the photons released in nuclear reactions in the core of the Sun to exit the photosphere?

A) 8 minutes
B) 16 hours
C) 1,000 years
D) 100,000 years
E) 4.6 billion years

Question 27

The majority of the Sun's energy comes from:

A) gravitational contraction
B) nuclear fission of uranium
C) hydrogen fusion
D) helium burning
E) burning material as in a fire

Question 28

The detection of solar neutrinos confirms that:

A) the Sun's core is powered by proton-proton fusion
B) energy transport by radiation occurs throughout much of the solar interior
C) magnetic fields are responsible for surface activity on the Sun
D) convection churns the base of the solar atmosphere
E) sunspots are cooler than the rest of the photosphere

Question 29

If neutrinos oscillated between five different types of neutrino during their transit from the Sun to Earth, then how many neutrinos would we have detected compared to what was emitted by the Sun?

A) one-half as many
B) one-third as many
C) one-fourth as many
D) one-fifth as many
E) We would detect no neutrinos.

Question 30

The net effect of the proton-proton chain is that four hydrogen nuclei are converted to one helium nucleus and _________ are released.

A) visible wavelength photons
B) gamma ray photons, positrons, and neutrinos
C) ultraviolet photons and neutrinos
D) X-ray photons, electrons, and neutrinos
E) infrared photons and positrons

Question 31

If the Sun converts 5*10¹¹ kg of H to He per second and 10 percent of the Sun's total mass is available for nuclear burning, how long might we expect the Sun to live?

A) 10⁴ years
B) 10⁸ years
C) 10¹⁰ years
D) 10¹¹ years
E) 10¹⁴ years

Question 32

Which of the following method(s) is (are) NOT used to transport energy from the core of the Sun to its surface?

A) radiation
B) convection
C) conduction
D) All of the above are important in the solar interior.
E) None of the above are important in the solar interior.

Question 33

The energy that fuels the Sun is generated:

A) only on its surface
B) only in its core
C) only in the solar wind
D) both in its core and on its surface
E) in its core, on the surface, and in the solar wind

Question 34

When two atomic nuclei come together to form a new species of atom, this is called:

A) nuclear fission
B) nuclear recombination
C) nuclear splitting
D) nuclear fusion
E) ionization

Question 35

If you hold on to one end of a metal spoon while placing the other end in a pot of boiling water, you will burn your hand. This is an example of energy being transported by:

A) radiation
B) convection
C) conduction
D) convection and radiation
E) radiation and conduction

Question 36

When you turn on the heater in a car, the passengers in the front seat warm up first, then eventually the warm air gets to the passengers in the back seat. This is an example of energy being transported by:

A) radiation
B) convection
C) conduction
D) convection and conduction
E) radiation and conduction

Question 37

Which of these can travel directly from the center of the Sun to Earth in about 8 minutes?

A) photons
B) electrons
C) protons
D) neutrons
E) neutrinos

Question 38

What do astronomers mean when they say that the Sun makes energy by hydrogen burning?

A) The Sun is combusting hydrogen in a fire and releasing energy.
B) The Sun is fusing hydrogen into uranium and releasing energy.
C) The Sun is made of mostly hydrogen at very high temperature.
D) The Sun is fusing hydrogen into helium and releasing energy.
E) The Sun is accumulating hydrogen from the solar wind and releasing energy.

Question 39

If the core of the Sun were hotter than it is now, how would the Sun's energy production change?

A) It would produce less energy per second than it does now.
B) It would produce more energy per second than it does now.
C) Its energy production would vary more than it does now.
D) Its energy production would be more stable than it is now.
E) The Sun's energy production would not change.

Question 40

Which of the following layers of the Sun makes up the majority of its interior?

A) the core
B) the radiative zone
C) the convective zone
D) the photosphere
E) the chromosphere

Question 41

We know the Sun's corona is very hot because:

A) we observe it emitting radiation at visible wavelengths
B) the chromosphere and the photosphere are that hot, too
C) we observe absorption from highly ionized atoms of iron and calcium in its spectrum
D) the gas emits most of its radiation at radio wavelengths
E) all of the above

Question 42

The surface of the Sun appears sharp when we look at it in visible light because:

A) the photosphere is cooler than the layers below it
B) the photosphere is thin compared to the other layers in the Sun
C) the photosphere is much less dense than the convection zone
D) the photosphere is transparent to radiation
E) the Sun has a distinct surface

Question 43

Which of the following is NOT a result of an increase in solar activity?

A) The altitudes of orbiting satellites decrease.
B) Airplanes have trouble navigating.
C) Stronger auroras are seen.
D) Power grids can be damaged.
E) All of the above can be caused by increased solar activity.

Question 44

Which of the following are created by solar magnetic activity?

A) sunspots
B) prominences
C) coronal mass ejections
D) solar flares
E) all of the above

Question 45

By studying how the surface of the Sun vibrates like a struck bell we can determine its:

A) age
B) interior density
C) total mass
D) size
E) temperature

Question 46

The darkest part of a sunspot is called the:

A) penumbra
B) umbra
C) granule
D) photosphere
E) magnetic field

Question 47

Sunspots appear dark because they have _________ than the surrounding gas.

A) higher densities
B) lower densities
C) higher pressures
D) lower temperatures
E) higher temperatures

Question 48

Imagine that you observed the Sun and measured the brightness of the face of the Sun at the locations marked in this image: At which of these locations would you measure the lowest brightness?

A) A
B) B
C) C
D) D
E) They would all have the same brightness.

Question 49

The Sun's corona has a temperature of approximately 1 million degrees. At what wavelength and in what part of the electromagnetic spectrum does its radiation peak?

A) 550 nm, visible
B) 2 *10^-5 m, infrared
C) 4 *10^-7 m, ultraviolet
D) 3 *10^-9 m, X-rays
E) 6 m, radio

Question 50

Which of the layers of the Sun is located the furthest from the center of the Sun?

A) chromosphere
B) photosphere
C) radiative zone
D) convective zone
E) corona

Question 51

The Sun's chromosphere appears red because:

A) it is hotter than the photosphere
B) as the Sun rotates, the chromosphere appears to move away from us radially
C) it has a higher concentration of heavy metals
D) it is made of mostly helium
E) its spectrum is dominated by H $\alpha$ emission

Question 52

If a sunspot appears one-quarter as bright as the surrounding photosphere, and the average temperature of the photosphere is 5800 K, what is the temperature of the gas in this sunspot?

A) 3625 K
B) 4100 K
C) 4500 K
D) 5200 K
E) 5500 K

Question 53

The best wavelength to use to observe a solar prominence is:

A) 550 nm, green visible light
B) 656 nm, a red hydrogen emission line
C) 16 mm, an ultraviolet emission line
D) 21 cm, microwave emission
E) 0.02 nm, X-ray emission

Question 54

The image below taken at visible wavelengths shows a section of the Sun with sunspots visible. Which of the labeled regions is the lowest temperature?

A) region A
B) region B
C) region C
D) They are all the same temperature.
E) There is not enough information to determine their relative temperatures.

Question 55

What keeps the gas in the Sun's corona from flying away from the Sun?

A) gravity
B) strong nuclear force
C) the Sun's magnetic field
D) the solar wind
E) sunspots

Question 56

We can determine how the density changes with radius in the Sun using:

A) radar observations
B) neutrino detections
C) high-energy (gamma ray) observations
D) helioseismology
E) infrared observations

Question 57

The magnetic field of the Sun is continuously produced and deformed by:

A) its differential rotation
B) the solar wind
C) changes in the rate of nuclear fusion in the core
D) a liquid conducting layer in the interior
E) This is a trick question. The solar magnetic field is primordial.

Question 58

The solar spectrum is an example of a(n) _________ spectrum.

A) emission
B) absorption
C) continuum
D) blackbody
E) X-ray

Question 59

The solar neutrino problem was solved by:

A) adjusting the rate of hydrogen burning in solar models
B) improving detector efficiencies so more neutrinos were observed
C) postulating that neutrinos had mass and oscillated between three different types
D) lowering the percentage of helium in models of solar composition
E) correctly measuring the density of the Sun's interior

Question 60

The image below shows the Sun during a solar eclipse at visible wavelengths. Which part of the Sun is visible around the shadow of the Moon?

A) chromosphere
B) photosphere
C) radiative zone
D) convective zone
E) corona

Question 61

Solar wind particles hit the surface of the Moon, but they don't make it to the surface of the Earth because the Earth:

A) is larger than the Moon
B) is warmer than the Moon
C) has an atmosphere while the Moon does not
D) has a magnetic field while the Moon does not
E) is further from the Sun than the Moon

Question 62

The Sun's internal magnetic field becomes tangled up over time because of:

A) coronal holes
B) coronal mass ejections
C) differential rotation
D) temperature changes in the Sun's core
E) all of the above

Question 63

In the proton-proton chain, the net reaction is that 4 protons are converted into 1 helium nucleus. What other byproducts are released in this reaction, and why?

Question 64

Explain why magnetic fields trap coronal gas over much of the solar surface but allow it to escape in coronal holes.

Question 65

In the text we considered the case of a "too-large" Sun. Show that a star with the same mass, composition, radius, and luminosity as the Sun, but with a higher temperature (that is, a "too-hot" Sun), also leads to a contradiction.

Question 66

What is "limb darkening"? Explain why limb darkening occurs in the Sun.

Question 67

The Sun's magnetic field reverses direction every:

A) 24 hours
B) 27 days
C) 12 months
D) 11 years
E) 22 years

Question 68

Through hydrogen fusion, the Sun loses approximately 4 million tons of mass each second. If it burns hydrogen at this rate for 10 billion years, what percentage of its original mass will it lose in all? (Note: The mass of the Sun is 1.99*10³⁰ kg, and 1 ton = 1,000 kg.)

Question 69

The Maunder Minimum was a 60-year period when:

A) debris thrown up in a comet collision blanketed the Sun
B) almost no sunspots occurred on the Sun
C) the Voyager 2 spacecraft traversed the heliopause
D) very few dust storms occurred on Mars
E) very few volcanic eruptions occurred on Mars

Question 70

Calculate the amount of energy released by converting four hydrogen atoms into one helium atom. The mass of a hydrogen atom is 1.67 * 10^-24g; the mass of a helium atom is 6.65 *10^-24
g. The speed of light is 3 * 10⁸ m/s.

Question 71

The picture below shows a diagram of the Sun with zones labeled A, B, and C. Explain how energy is being transferred in each of the three regions.

Question 72

If a coronal mass ejection occurs on the Sun that expels material at a speed of 800 km/s, how long will it take these charged particles to reach the Earth?

A) 0.7 day
B) 1.4 days
C) 1.8 days
D) 2.2 days
E) 3.5 days

Question 73

Explain why hydrostatic equilibrium results in the center of the Sun having the highest pressure and temperature.

Question 74

If you observe a maximum number of sunspots right now, how long would you have to wait to see the next solar maximum?

A) 24 hours
B) 6 months
C) 1 year
D) 11 years
E) 22 years

Question 75

When solar activity is very high, the Earth's atmosphere will:

A) expand
B) contract
C) remain approximately the same
D) repel charged particles
E) block out sunlight

Question 76

Why is hydrogen burning the main energy source for main-sequence stars? Give at least two reasons.

Question 77

In addition to the laws of physics and chemistry, what information do we need to know about our Sun to calculate its internal structure and radius?

Question 78

Explain why the solution to the solar neutrino problem is an excellent example of how observations drive the evolution of science.

Question 79

When is the Sun most luminous?

A) when there are a maximum number of sunspots
B) when there are a average number of sunspots
C) where there a minimum number of sunspots
D) the Sun's luminosity does not change
E) the Sun's luminosity changes, but it has no relation to the number of sunspots

Question 80

List three methods of energy transport in nature and explain how the energy is being transferred in each of those methods. Which two are means by which energy is transported inside the Sun?