Astronomy Chapter 14

In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot thanks togravitationalcontraction. What was the major drawback of this idea?D.)It predicted that the Sun could last only about 25 million years, which is far less than the ageof Earth.
When is/was gravitational contraction an important energy-generation mechanism for the Sun?C)when the Sun was being formed from a collapsing cloud of gas
What do we mean when we say that the Sun is ingravitational equilibrium?D)There is a balance within the Sun between the outward push of pressure and the inward pullof gravity.
What two forces are balanced in what we callgravitational equilibrium?B)outward pressure and gravity
What is the Sun made of?B)70 percent hydrogen, 28 percent helium, 2 percent other elements
The phase of matter in the Sun isD)plasma.
What are the appropriate units for the Sun’sluminosity?B)watts
What is the average temperature of thesurface of the Sun?D)6,000 K
Which is closest to the temperature of thecore of the Sun?D)10 million K
From the center outward, which of the following lists the “layers” of the Sun in the correct order?D)core, radiation zone, convection zone, photosphere, chromosphere, corona
Which layer of the Sun do we normally see?C)photosphere
The core of the Sun isD)hotter and denser than the surface
Based on its surface temperature of 5,800 K, what color are most of the photons that leave the Sun’ssurface?E)green
Why do sunspots appear dark in pictures of the Sun?D)They actually are fairly bright but appear dark against the even brighter background of thesurrounding Sun.
Sunspots are cooler than the surrounding solar surface becauseD)strong magnetic fields slow convection and prevent hot plasma from entering the region.
How does the Sun generate energy today?E)nuclear fusion
How do human-built nuclear power plants on Earth generate energy?D)nuclear fission
Hydrogen fusion in the Sun requires a temperature (in Kelvin) ofC)millions of degrees.
19)At the center of the Sun, fusion converts hydrogen intoA)helium, energy, and neutrinos.
How much mass does the Sun lose through nuclear fusion per second?A)4 million tons
Suppose you put two protons near each other. Because of the electromagnetic force, the twoprotons willE.)repel each other.
Which is the strongest of the fundamental forces in the universe?B)strong force
The first step in the proton-proton chain produces an antielectron, orpositron. What happens to thepositron?C)It is rapidly converted to energy when it meets an ordinary electron, resulting inmatter-antimatter annihilation.
The overall fusion reaction by which the Sun currently produces energy isB.) 4 H 1 He+ energy.
Why must the Sun’s rate of fusion gradually rise over billions of years?D)Fusion reactions decrease the overall number of particles in the core, causing the core toshrink, converting gravitational potential energy into thermal energy, and increasing the rateof fusion.
Suppose that, for some unknown reason, the core of the Sun suddenly became hotter. Which of thefollowing best describes what would happen?B.)Higher temperature would cause the rate of nuclear fusion to rise, which would increase theinternal pressure, causing the core to expand and cool until the fusion rate returned to normal.
27)How do we know what goes on under the surface of the Sun?E)both B and D
Studies of sunquakes, orhelioseismology, have revealed thatE)our mathematical models of the solar interior are fairly accurate.
Which statement best describes thesolar neutrino problem?B)Solar neutrinos have been detected, but in fewer numbers than predicted by theoreticalmodels.
Why are neutrinos so difficult to detect?A)because they rarely interact with matter
Which of the following statements about neutrinos isnot true?E)The mass of a neutrino is 30 percent of the mass of an electron.
What is a possible solution to thesolar neutrino problem?B)The electron neutrinos created in the Sun change into another type of neutrino that we do notdetect.
The light radiated from the Sun’s surface reaches Earth in about 8 minutes, but the energy of thatlight was released by fusion in the solar core aboutA)a million years ago.
What happens to energy in theconvection zone of the Sun?A)Energy is transported outward by the rising of hot plasma and the sinking of cooler plasma.
Most of the energy produced in the Sun is released in the form of visible light from thephotosphere. However, some energy is released from the upper layers of the solar atmosphere.Which of the following best describes where other forms of light are released?B)The chromosphere is the source of ultraviolet light, and the corona is the source of X rays.
What is granulation in the Sun?E) the bubbling pattern on the photosphere produced by the underlying convection
What arecoronal holes?A) areas of the corona where magnetic field lines project into space, allowing charged particles toescape the Sun, becoming part of the solar wind
Which of the following statements about the sunspot cycle is not true?C.) The rate of nuclear fusion in the Sun peaks about every 11 years.
What processes are involved in the sunspot cycle?C.) The winding of magnetic field lines due to differential rotation
What observations characterize solar maximum?C.) We see many sunspots on the surface of the Sun.
Humans have not sent a spacecraft into the interior of the Sun to confirm any models of the interior.What evidence then do we have to support our current ideas about the solar interior?B)solar neutrinos