Astronomy Test 3: Sun and Stars

Why must the Sun's rate of fusion gradually rise over billions of years? a) 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. b) The rate of fusion is not rising; it is actually decreasing over time. 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 Sun becomes less efficient and must increase the rate of fusion to produce the same amount of energy.

a) 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.

The corona and chromosphere are hotter than the photosphere. a) True b) False

a) True

Suppose you put two protons near each other. Because of the electromagnetic force, the two protons will a) repel each other. b) remain stationary. c) collide. d) join together to form a nucleus. e) attract each other.

a) repel each other.

What is the average temperature of the surface of the Sun? a) 100,000 K b) 6,000 K c) 10,000 K d) 1,000 K e) 1 million K

b) 6,000 K

How is the sunspot cycle directly relevant to us here on Earth? a) The sunspot cycle strongly influences Earth's weather. b) Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment. 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.

b) Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.

Nuclear power plants on Earth create energy in the same way as the Sun. a) True b) False

b) False

The Sun generates energy primarily by nuclear fission. a) True b) False

b) False

The chromosphere is the layer of the Sun that we see as its visible surface. a) True b) False

b) False

What observations characterize solar maximum? a) The Sun rotates faster at the equator. b) We see many sunspots on the surface of the Sun. c) The Sun becomes much brighter. d) The Sun emits light of longer average wavelength. e) all of the above

b) We see many sunspots on the surface of the Sun.

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

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

The core of the Sun is a) constantly rising to the surface through convection. b) hotter and denser than the surface. c) composed of iron. d) at the same temperature and density as the surface. e) at the same temperature but denser than the surface.

b) hotter and denser than the surface.

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 surface tension c) gravitational force and outward pressure d) the strong force and the electromagnetic force

c) gravitational force and outward pressure

Based on its surface temperature of 5,800 K, what color are most of the photons that leave the Sun's surface? a) yellow b) blue c) green d) red e) orange

c) green

The phase of matter in the Sun is a) liquid. b) gas. c) plasma. d) solid. e) a mixture of all of the above

c) plasma.

What is granulation in the Sun? a) dust particles in the Sun that haven't been turned into plasma b) elements in the Sun other than hydrogen and helium c) the bubbling pattern on the photosphere produced by the underlying convection d) lumps of denser material in the Sun e) another name for the way sunspots look on the surface of the Sun

c) the bubbling pattern on the photosphere produced by the underlying convection

What are the appropriate units for the Sun's luminosity? a) kilograms b) Newtons c) watts d) joules e) meters

c) watts

What is the Sun made of? a) 98 percent hydrogen, 2 percent helium and other elements b) 50 percent hydrogen, 25 percent helium, 25 percent other elements c) 100 percent hydrogen and helium d) 70 percent hydrogen, 28 percent helium, 2 percent other elements e) 70 percent helium, 28 percent hydrogen, 2 percent other elements

d) 70 percent hydrogen, 28 percent helium, 2 percent other elements

Which of the following statements about the sunspot cycle is not true? a) The cycle is truly a cycle of magnetic activity, and variations in the number of sunspots are only one manifestation of the cycle. b) The number of solar flares peaks about every 11 years. c) The number of sunspots peaks approximately every 11 years. d) The rate of nuclear fusion in the Sun peaks about every 11 years. e) With each subsequent peak in the number of sunspots, the magnetic polarity of the Sun is the reverse of the previous peak.

d) The rate of nuclear fusion in the Sun peaks about every 11 years.

Which layer of the Sun do we normally see? a) corona b) convection zone c) radiation zone d) photosphere e) chromosphere

d) photosphere

Why do sunspots appear dark in pictures of the Sun? a) They are holes in the solar surface through which we can see to deeper, darker layers of the Sun. b) They are too cold to emit any visible light. c) They emit light in other wavelengths that we can't see. d) They are tiny black holes, absorbing all light that hits them. e) They actually are fairly bright but appear dark against the even brighter background of the surrounding Sun.

e) They actually are fairly bright but appear dark against the even brighter background of the surrounding Sun.

At the center of the Sun, fusion converts hydrogen into a) hydrogen compounds. b) radiation and elements like carbon and nitrogen. c) plasma. d) radioactive elements like uranium and plutonium. e) helium, energy, and neutrinos.

e) helium, energy, and neutrinos.