Deck 11: Our Star: The Sun

Question 1

If the Sun stopped nuclear fusion in its core,it would take 100 years for its luminosity to change.

Answer 1

False

Question 2

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

Answer 2

False

Question 3

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

Answer 3

True

Question 4

The solar magnetic field switches polarity every 11 years.

Question 5

Opacity in the interior of the Sun allows efficient release of energy to surrounding layers.

Question 6

The majority of the Sun's energy comes from:

A) gravitational contraction
B) its rapid rotation
C) hydrogen fusion
D) helium burning

Question 7

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

Question 8

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

Question 9

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

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

Question 10

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

Question 11

Sunspots generally occur in pairs with opposite polarity.

Question 12

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

Question 13

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

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

Question 14

The energy that fuels the Sun is generated:

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

Question 15

The Sun has a mass of:

A) 2 × 10³⁰ kg
B) 2 × 10¹⁰ kg
C) 2 × 10²⁰ kg
D) 2 × 10⁴⁰ kg

Question 16

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

Question 17

Nuclei of atoms are held together by gravity.

Question 18

Examine the figure below.In a sunspot,the umbra is cooler than the penumbra.

Question 19

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

Question 20

In the proton-proton chain,the net result is that 4 protons are converted into 1 helium nucleus and energy,electrons,and neutrinos are released.

Question 21

Detection of solar neutrinos confirms that:

A) the core is powered by proton-proton fusion
B) 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

Question 22

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 billions 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

Question 23

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) 2.1 days

Question 24

Sunspots appear dark because:

A) they have lower densities
B) they have lower rotation rates
C) they have lower temperatures
D) they are storm systems like those on the Jovian planets

Question 25

Examine the figure below.The interior zones of the Sun are distinguished by:

A) jumps in density between zones
B) their temperature profiles
C) their modes of energy transport
D) all of the above

Question 26

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) All the above are valid reasons.

Question 27

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

Question 28

Which of the following methods is not used to transport energy from the core to the surface of the Sun?

A) Radiation
B) Convection
C) Conduction
D) All of the above are important in the solar interior.

Question 29

The solar neutrino problem was solved by:

A) adjusting the rates 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

Question 30

Examine the figure below.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

Question 31

Which of the following are manifestations of solar magnetic activity?

A) Sunspots
B) Prominences
C) Flares
D) All of the above

Question 32

Hydrostatic equilibrium is a balance between:

A) heat and rotation
B) core temperature and surface temperature
C) pressure and gravity
D) radiation and heat

Question 33

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

A) 5.5 × 10^-7 m,visible
B) 2 × 10^-5 m,infrared
C) 4 × 10^-7 m,ultraviolet
D) 3 × 10^-9 m,X-rays

Question 34

The Sun's magnetic field reverses direction every:

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

Question 35

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

Question 36

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

Question 37

Light from the 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

Question 38

In the proton-proton chain,the net reaction is that 4 hydrogen nuclei are converted to 1 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

Question 39

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-third as many
B) One-fourth as many
C) One-fifth as many
D) We would detect no neutrinos

Question 40

Density,temperature,and pressure increase as you move inward in the interior of the Sun.This means that the force of gravity,(F_g = 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 41

In the figure below,label the regions of the Sun.

Question 42

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

A) expand
B) contract
C) remain approximately the same
D) repel charged particles

Question 43

Examine the figure below.Show where in the Sun nuclear fusion occurs and explain why fusion occurs there.

Question 44

The 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) its spectrum is dominated by H $\alpha$ emission

Question 45

What are the three ways in which energy could be transported within a star (or to your fingers)? Explain your answer.

Question 46

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

Question 47

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

A) The height of orbiting satellites decreases.
B) Airplanes have trouble navigating.
C) Stronger auroras are seen.
D) All of the above can be caused by increased solar activity.

Question 48

If a sunspot appears one-quarter as bright as the surrounding photosphere,and the average temperature of the photosphere is 5,800 K,what is the temperature of the gas in this sunspot?

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

Question 49

The surface of the Sun appears sharp 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

Question 50

Examine the figure below.Explain why it takes so long for gamma-ray energy to find its way to the outer layers of the Sun.

Question 51

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

Question 52

Magnetic field is continuously produced and deformed in the Sun by:

A) differential rotation
B) fusion reactions in the core
C) a liquid conducting layer in the interior
D) This is a trick question.The solar magnetic field is primordial

Question 53

We know the corona of the Sun is very hot because:

A) we observe it emitting large amounts of radio emission
B) the chromosphere and the photosphere are so hot
C) we observe emission from highly ionized atoms of iron and calcium
D) all of the above

Question 54

The Maunder Minimum was a 60-year period when:

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

Question 55

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

A) coronal holes
B) coronal mass ejections
C) differential rotation
D) all of the above

Question 56

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

Question 57

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) 10¹⁴ years

Question 58

The best wavelength to use to observe a solar prominence or flare 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

Question 59

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 m²kg/s³.

A) 7 × 10³⁷ reactions per second; 3 × 10²⁶ watt
B) 3 × 10³⁸ reactions per second; 10²⁷ watt
C) 3 × 10³⁸ reactions per second; 4 × 10²⁶ watt
D) 7 × 10³⁷ reactions per second; 5 × 10²⁵ watt

Question 60

The solar spectrum (see the image below)is an example of a(n)__________ spectrum.

A) emission
B) absorption
C) continuum
D) blackbody

Question 61

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

Question 62

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

Question 63

How do periods of strong solar activity affect near-Earth orbiting spacecraft?

Question 64

If a coronal mass ejection occurred on the Sun and ejected particles toward the Earth that traveled at the speed of 1,000 km/s,how long would it take them to reach Earth?

Question 65

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

Question 66

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

Question 67

When,during its 11-year cycle,is the Sun most luminous? What might this have to do with the Maunder Minimum?

Question 68

Calculate the amount of energy released by converting 4 hydrogen atoms into 1 helium atom.The mass of a hydrogen atom is 1.67 × 10^-24 kg; the mass of a helium atom is 6.65 × 10^-24 g.The speed of light is 3 × 10⁸ m/s.

Question 69

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),leads to a contradiction.

Question 70

If a sunspot is half as bright as the surrounding photosphere of the Sun,what is the approximate temperature of the gas in the sunspot if the photosphere's average temperature is 5800 K?

Question 71

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.)