Chapter 11

What is the Sun made of (by mass)? 70% hydrogen, 28% helium, 2% other elements 100% hydrogen and helium 90% dark matter, 10% ordinary matter 50% hydrogen, 25% helium, 25% other elements

When we say that the Sun is a ball of plasma, we mean that ________. the Sun is made of atoms and molecules the Sun is roughly the same color as blood the Sun is made of material that acts like a liquid acts on Earth the Sun consists of gas in which many or most of the atoms are ionized (missing electrons)

The proton-proton chain is ________. an alternative way of generating energy that is different from the fusion of hydrogen into helium the linkage of numerous protons into long chains the specific set of nuclear reactions through which the Sun fuses hydrogen into helium another name for the force that holds protons together in atomic nuclei

Which of the following correctly compares the Sun's energy generation process to the energy generation process in human-built nuclear power plants? The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei. The Sun generates energy through fission while nuclear power plants generate energy through fusion. The Sun generates energy through nuclear reactions while nuclear power plants generate energy through chemical reactions. Both processes involve nuclear fusion, but the Sun fuses hydrogen while nuclear power plants fuse uranium.

Which of these layers of the Sun is coolest? core radiation zone photosphere

Which of these groups of particles has the greatest mass? a helium nucleus with two protons and two neutrons four electrons four individual protons

Scientists estimate the central temperature of the Sun using probes that measure changes in Earth's atmosphere. mathematical models of the Sun. laboratories that create miniature versions of the Sun.

At the center of the Sun, fusion converts hydrogen into plasma. radiation and elements like carbon and nitrogen. helium, energy, and neutrinos.

Sunspots appear darker than their surroundings because they block some of the sunlight from the photosphere. are cooler than their surroundings. do not emit any light.

What causes the cycle of solar activity? changes in the speed of the solar wind changes in the organization of the Sun's magnetic field changes in the Sun's fusion rate

According to modern science, approximately how old is the Sun? 11,000 years 4.5 billion years 25 million years 400 million years

What two physical processes balance each other to create the condition known as gravitational equilibrium in stars? the strong force and the weak force gravitational force and surface tension gravitational force and outward pressure the strong force and the electromagnetic force

Which of the following changes would cause the fusion rate in the Sun's core to increase? Check all that apply. an increase in the core temperature an increase in the core radius a decrease in the core temperature a decrease in the core radius

Which of the following must occur for a star's core to reach equilibrium after an initial change in fusion rate? Check all that apply. If the fusion rate initially decreases, then the core expands. If the fusion rate initially increases, then the core expands. If the fusion rate initially decreases, then the core contracts. If the fusion rate initially increases, then the core contracts.

What would happen if the fusion rate in the core of the Sun were increased but the core could not expand? The Sun's core would start to cool down, and the rate of fusion would decrease. The Sun's core would reach a new equilibrium at a lower temperature. The Sun's core would reach a new equilibrium at a higher temperature. The Sun's core would start to heat up, and the rate of fusion would increase even more.

Which of the following is the best answer to the question, "Why does the Sun shine?" The Sun initially began making energy through chemical reactions. These heated the interior enough to allow gravitational contraction and nuclear fusion to occur. As the Sun was forming, nuclear fusion reactions in the shrinking clouds of gas slowly became stronger and stronger, until the Sun reached its current luminosity. As the Sun was forming, gravitational contraction increased the Sun's temperature until the core became hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine. The Sun initially began generating energy through nuclear fusion as it formed, but today it generates energy primarily through the sunspot cycle.

What is the solar wind? the strong wind that blows sunspots around on the surface of the Sun a stream of charged particles flowing outward from the surface of the Sun the uppermost layer of the Sun, lying just above the corona the wind that causes huge arcs of gas to rise above the Sun's surface

Which of the following is the phase of matter in the Sun? solid liquid plasma gas a mixture of all of the above

The Sun's surface seethes and churns with a bubbling pattern. Why? The churning gas is being stirred up by the strong solar wind. The churning is an illusion created by varying radiation, as the gas on the Sun's surface is actually quite still. The Sun's surface is boiling. We are seeing hot gas rising and cool gas falling due to the convection that occurs beneath the surface.

To estimate the central temperature of the Sun, scientists _________. use hot gas to create a small Sun in a laboratory monitor changes in Earth's atmosphere send probes to measure the temperature use computer models to predict interior conditions

In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot due to gravitational contraction. What was the major drawback to this idea? It is physically impossible to generate heat simply by making a star shrink in size. It predicted that the Sun would shrink noticeably as we watched it, but the Sun appears to be stable in size. It predicted that Earth would also shrink in size with time, which would make it impossible to have stable geology on our planet. It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.

Every second, the Sun converts about 600 million tons of hydrogen into 596 million tons of helium. The remaining 4 million tons of mass is ________. reabsorbed as molecular hydrogen ejected into space in a solar wind ejected into space by solar flares converted to an amount of energy equal to 4 million tons times the speed of light squared

If the Sun's core suddenly shrank a little bit, what would happen in the Sun? The density of the core would decrease, causing the core to cool off and expand. The core would cool off and continue to shrink as its density increased. The core would heat up, fusion rates would increase, the core would re-expand. The core would heat up, causing it to radiate so much energy that it would shrink even more.

Why does the Sun emit neutrinos? Solar flares create neutrinos with magnetic fields. The Sun was born with a supply of neutrinos that it gradually emits into space. Convection releases neutrinos, which random walk through the radiation zone. Fusion in the Sun's core creates neutrinos. The Sun does not emit neutrinos.

Why do sunspots appear dark in pictures of the Sun? They are too cold to emit any visible light. They are extremely hot and emit all their radiation as X-rays rather than visible light. They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere. They are holes in the solar surface through which we can see through to deeper, darker layers of the Sun.

A computer accessory salesman attempts to convince you to purchase a "solar neutrino" shield for your new computer. (It's even "on sale"!) Why do you turn down this excellent offer? There's no such thing as a solar neutrino. The Earth's natural magnetic field already offers excellent protection against the onslaught of solar neutrinos. Neutrinos rarely, if ever, interact with your computer. Solar neutrinos are generated by solar winds, but we're in a solar minimum now, so the risk of damage is very low.

Satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because ________. it is too dangerous to send the Space Shuttle to service satellites during solar maximum of increased magnetic interference Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits they are more likely to have their electronics "fried" by a solar flare during solar maximum

The source of energy that keeps the Sun shining today is ________. nuclear fission nuclear fusion gravitational contraction chemical reactions

Energy balance in the Sun refers to a balance between ________. 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 the amount of energy the Sun radiates into space and the amount of energy that reaches Earth the force of gravity pulling inward and the force due to pressure pushing outward the mass that the Sun loses each second and the amount of mass converted into energy each second

Why are neutrinos so difficult to detect? They are extremely rare. They have no mass. They have a tendency to pass through just about any material without any interactions. No one knows; this is the essence of the "solar neutrino problem."

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 ________. one hundred years ago three days ago a few hundred thousand years ago one thousand years ago

What do sunspots, solar prominences, and solar flares all have in common? They all have about the same temperature. They are all strongly influenced by magnetic fields on the Sun. They are all shaped by the solar wind. They all occur only in the Sun's photosphere.

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

Which is closest to the temperature of the Sun's core? 10,000 K 1 million K 100,000 K 10 million K 100 million K

What keeps the Sun's outer layers from continuing to fall inward in a gravitational collapse? neutrinos produced by nuclear fusion drag gas outward outward pressure due to super-heated gas electromagnetic repulsion between protons the strong force between protons

Which of the following correctly describes how the process of gravitational contraction can make a star hot? Gravitational contraction involves the generation of heat by chemical reactions, much like the burning of coal. Gravitational contraction involves nuclear fusion, which generates a lot of heat. Heat is generated when gravity contracts, because gravity is an inverse square law force. When a star contracts in size, gravitational potential energy is converted to thermal energy.

From center outward, which of the following lists the "layers" of the Sun in the correct order? core, corona, radiation zone, convection zone, photosphere, chromosphere core, convection zone, radiation zone, corona, chromosphere, photosphere core, radiation zone, convection zone, corona, chromosphere, photosphere core, radiation zone, convection zone, photosphere, chromosphere, corona