Chapter 14 – Quiz 14 – Flashcards

Which of the following is the best answer to the question, "Why does the Sun shine?" As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes 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. The Sun initially began generating energy through nuclear fusion as it formed, but today it generates energy primarily through the sunspot cycle.

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 _________. converted to an amount of energy equal to 4 million tons times the speed of light squared ejected into space in a solar wind reabsorbed as molecular hydrogen ejected into space by solar flares

How can we best observe the Sun's chromosphere and corona? The chromosphere is best observed with infrared telescopes and the corona is best observed with ultraviolet telescopes. The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes. The chromosphere and corona are both best studied with radio telescopes. The chromosphere and corona are both best studied with visible light.

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 through fission while nuclear power plants generate energy through fusion. Both processes involve nuclear fusion, but the Sun fuses hydrogen while nuclear power plants fuse uranium. The Sun generates energy through nuclear reactions while nuclear power plants generate energy through chemical reactions. The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.

How does the Sun's mass compare to Earth's mass? The Sun's mass is about 300 times the mass of the Earth. Both have approximately the same mass. The Sun's mass is about 30 times the mass of the Earth. The Sun's mass is about 300,000 times the mass of the Earth.

When is/was gravitational contraction an important energy generation mechanism for the Sun? It is important during periods when the Sun is going from solar maximum to solar minimum. It has played a role throughout the Sun's history, but it was most important right after nuclear fusion began in the Sun's core. It is the primary energy generation mechanism in the Sun today. It was important when the Sun was forming from a shrinking interstellar cloud of gas.

If the Sun suddenly stopped emitting neutrinos, what might we infer (after checking that our neutrino detectors were still operational)? Fusion reactions in the Sun have ceased. Fusion reactions in the Sun ceased a few hundred thousand years ago. The Sun has exhausted its supply of neutrinos. Fission reactions in the Sun have ceased.

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

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 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. It predicted that the Sun would shrink noticeably as we watched it, but the Sun appears to be stable in size.

The star Alpha Centauri A is the same type of star as the Sun, but its luminosity is about 1.6 times that of the Sun. What can we conclude? Alpha Centauri A has a much higher surface temperature than the Sun. Alpha Centauri A is much farther from Earth than the Sun. Alpha Centauri A must have a vastly different interior structure than the Sun. Alpha Centauri A fuses hydrogen into helium in its core at a higher rate than our Sun.

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 Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits of increased magnetic interference they are more likely to have their electronics "fried" by a solar flare during solar maximum

The Sun's surface seethes and churns with a bubbling pattern. Why? The Sun's surface is boiling. 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. We are seeing hot gas rising and cool gas falling due to the convection that occurs beneath the surface.

The intricate patterns visible in an X-ray image of the Sun generally show _________. extremely hot plasma flowing along magnetic field lines structure within sunspots helioseismological fluctuations a bubbling pattern on the photosphere

Which of the following best describes why the Sun emits most of its energy in the form of visible light? Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light. Nuclear fusion in the Sun's core produces visible light photons. The visible light comes from energy level transitions as electrons in the Sun's hydrogen atoms jump between level 1 and level 2. The Sun's gas is on fire like flames from wood or coal, and these flames emit visible light.

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

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 heat up, causing it to radiate so much energy that it would shrink even more. The core would heat up, fusion rates would increase, the core would re-expand. The core would cool off and continue to shrink as its density increased.

Which of the following best explains why the Sun's luminosity gradually rises over billions of years? The planets need more and more energy to maintain any life on them as time goes on, and therefore the Sun must bet hotter. Fusion gradually decreases the number of independent particles in the core, allowing gravity to compress and heat the core, which in turn increases the fusion rate and the Sun's luminosity. The Sun's core gradually expands with time, and this expansion means there is more room for energy to be generated and hence increases the Sun's luminosity. Nuclear reactions in the Sun become more efficient with time, so that each fusion reaction releases more energy when the Sun is old than when it is young; this in turn raises the Sun's luminosity.

How can we measure the strength of magnetic fields on the Sun? Only by using sophisticated computer models, because there are no observational ways of measuring magnetic field strength. By observing auroras here on Earth. By looking for the splitting of spectral lines in the Sun's spectrum. By observing the sizes of sunspots: Bigger sunspots mean a stronger field.

Which of the following choices is not a way by which we can study the inside of the Sun? We can send a space probe into the Sun's photosphere. We can probe the interior of the Sun by studying the vibrations in its photosphere. We can study solar neutrinos. We can make a computer model of the Sun's interior that allow us to predict the observable properties of the Sun.