astronomy exam 2
Which galaxy type is shaped like a rugby ball? A Sb B SB0 C E0 D E5
D E5
A planetary nebula glows because Choose one: A. fusion is happening in the nebula. B. it is hot enough to emit UV radiation. C. light from the central star causes emission lines. D. it is heating up the interstellar medium around it.
c
A light-year is a measure of Choose one: A. time. B. distance. C. mass. D. speed.
b
18.3 What does gravity mean in relativity? ⓐ It is a result of mass and energy being the same thing. ⓑ It is a consequence of length contraction. ⓒ It is the result of masses acting larger when they move at high speeds. ⓓ It is the result of the distortion in spacetime around a massive object.
ⓓ It is the result of the distortion in spacetime around a massive object.
The huge amount of energy released in supernova explosions is strong enough to fuse nuclei together into elements heavier than iron. Because these elements cannot be created in ordinary stellar nuclear fusion, supernovae are the only natural source of them in the universe. Locate a periodic table of the elements such as the one in your book, and use it to determine which of the following elements are produced only in supernova explosions. Choose one or more: A. silver B. nitrogen C. copper D. calcium E. gold F. iron G. aluminum H. helium
silver copper gold
Based on hydrogen emission, where is star formation occurring? Choose one or more: No stars are forming. the right arm the left arm the central bulge
the right arm the left arm
rank the following in order of increasing size: sun solar system milky way virgo supercluster universe earth local group
1. earth 2. sun . solar system 4. milky way 5. local group 6. virgo supercluster 7. universe
rank the following in order of decreasing wavelength: infared ultraviolet radio waves visible gamma rays
1. radio waves 2. infared 3. visible 4. ultraviolet 5. gamma rays
Suppose an atom has three energy levels, specified in arbitrary units as 10, 7, and 5. In these units, which of the following energies might an emitted photon have? Choose one or more: A. 2 B. 4 C. 3 D. 5
2,3,5
Albireo, a star in the constellation of Cygnus, is a binary system whose two components can be seen easily with even a small telescope. Viewers describe the brighter star as "golden" and the fainter one as "sapphire blue." What does this tell you about the relative temperatures of the two stars? Choose one: A. The blue star is hotter than the gold star. B. The gold star is hotter than the blue star. C. The stars are the same temperature since they are a binary system. D. We can't tell anything about the temperatures of the stars from this information.
A
Are the brightest stars generally hotter or cooler than the Sun? Choose one: A. hotter B. cooler
A
From the vantage point of Earth in the diagram shown, how will the parallax of Star A compare to that of Star B? A. Star A has twice the parallax of Star B. B. Star A has the same parallax as Star B. C. Star A has four times the parallax of Star B. D. Star A has one-fourth the parallax of Star B. E. Star A has half the parallax of Star B.
A
Identify the element whose emission spectrum is shown in the graph by comparing it to the known spectra of five different elements.Choose one: A. helium B. neon C. sodium D. mercury E. hydrogen
A
subgiant
A star that is between being a main-sequence star and being a giant; subgiants have inert helium cores and hydrogen-fusing shells.
Phases of the interstellar medium include Choose one or more: A. cold, high-density gas. B. hot, low-density gas. C. cold, low-density gas. D. hot, high-density gas.
A, B, C
How does the energy production in a high-mass, main-sequence star differ from energy production in the Sun? Choose one or more: A. High-mass stars use carbon in a process that fuses hydrogen to helium. B. High-mass stars produce energy at a faster rate. C. High-mass stars burn carbon on the main sequence. D. High-mass stars get a lot of energy through non-nuclear processes.
A. High-mass stars use carbon in a process that fuses hydrogen to helium. B. High-mass stars produce energy at a faster rate.
While on the main sequence, a star is stable because there is a balance between its self-gravity trying to make the star collapse in on itself and the outward pressure of the gas heated by nuclear fusion trying to make it expand. When the core of a star runs out of fuel and nuclear fusion stops, what will happen to the star? A. It will collapse. B. Its size will stay the same, but it will suddenly cease emitting light. C. Its size will stay the same, but its light will slowly fade as it cools. D. It will expand.
A. It will collapse.
In a white dwarf, electrons are packed in so tightly that they physically cannot get any closer to one another. This provides an overall outward force, similar to the white dwarf's thermal pressure but much stronger, called electron degeneracy pressure, which does not depend on the temperature of the material. A white dwarf no longer has any ongoing energy production from nuclear fusion, so it will continuously cool off with time. Taking into consideration all the forces acting on each piece of the white dwarf, what will happen to it as it cools? Choose one: A. It will stay constant in size. B. It will become variable as it periodically expands and collapses. C. It will expand. D. It will collapse eventually into a singularity (a point).
A. It will stay constant in size.
The layers in a high-mass star occur in order of Choose one: A. fusion temperature. B. atomic abundance. C. spin state. D. atomic number.
A. fusion temperature.
For a galaxy, the term morphology refers to its Choose one: A. shape. B. overall density. C. motions of its stars. D. evolution over time.
A. shape.
The huge amount of energy released in supernova explosions is strong enough to fuse nuclei together into elements heavier than iron. Because these elements cannot be created in ordinary stellar nuclear fusion, supernovae are the only natural source of them in the universe. Locate a periodic table of the elements such as the one in your book, and use it to determine which of the following elements are produced only in supernova explosions. Choose one or more: A. silver B. nitrogen C. copper D. calcium E. gold F. iron G. aluminum H. helium
A. silver C. copper E. gold
Consider this information, and choose the property below that Type Ia supernova can help us measure. Choose one: A. the distance to a galaxy B. the composition of a galaxy C. the mass of a galaxy D. the radial velocity of a galaxy
a
Study the following figure. If it were possible to watch a high-mass star move to the right along one of the post-main-sequence lines, what would happen to the star's size? Choose one: A. It would become much larger. B. It would become much smaller. C. It would remain the same.
a
The cosmic microwave background radiation (CMB) indicates that the early universe Choose one: A. was quite uniform. B. varied greatly in density from one place to another. C. varied greatly in temperature from one place to another. D. was shaped differently from the modern universe.
a
Based on hydrogen emission, where is star formation occurring? Choose one or more: No stars are forming. the right arm the left arm the central bulge
right and left arm
Galaxies are classified according to A mass B color C density D shape
D shape
In a white dwarf, electrons are packed in so tightly that they physically cannot get any closer to one another. This provides an overall outward force, similar to the white dwarf's thermal pressure but much stronger, called electron degeneracy pressure, which does not depend on the temperature of the material. A white dwarf no longer has any ongoing energy production from nuclear fusion, so it will continuously cool off with time. Taking into consideration all the forces acting on each piece of the white dwarf, what will happen to it as it cools? Choose one: A. It will stay constant in size. B. It will become variable as it periodically expands and collapses. C. It will expand. D. It will collapse eventually into a singularity (a point).
A
Spectral type correlates directly with the temperature of the star. This is not enough to completely classify stars, however, because the luminosity of a star, and thus its exact position on the H-R diagram, depends on something else in addition to temperature. This is apparent from the H-R diagram because of the different populations of stars that exist in addition to the main sequence—they may have the same temperature as a main-sequence star, but a completely different luminosity.Based on the figure, what other property can we use to further classify stars? Choose one: A. radius B. composition C. rotation rate D. color
A
The layers in a high-mass star occur in order of Choose one: A. fusion temperature. B. atomic abundance. C. spin state. D. atomic number.
A
While on the main sequence, a star is stable because there is a balance between its self-gravity trying to make the star collapse in on itself and the outward pressure of the gas heated by nuclear fusion trying to make it expand. When the core of a star runs out of fuel and nuclear fusion stops, what will happen to the star?Choose one: A. It will collapse. B. Its size will stay the same, but it will suddenly cease emitting light. C. Its size will stay the same, but its light will slowly fade as it cools. D. It will expand.
A
Why does mass determine the main-sequence lifetime of a star? A Because more massive stars burn fuel faster and therefore have shorter lives. B Because more massive stars have more fuel and therefore have longer lives. C Because more massive stars burn different fuels and therefore have longer lives. D Because more massive stars have different initial compositions and therefore have shorter lives.
A Because more massive stars burn fuel faster and therefore have shorter lives.
What would the gas in an accretion disk do if there was no friction? A It would orbit indefinitely. B It would eventually fall in. C It would blow away.
A It would orbit indefinitely.
Suppose that your friend flies past you in a spaceship, and both of you measure the time it takes the spaceship to pass your location. Which of the following is true? A The time you measure is longer than the time your friend measures. B The time you measure is shorter than the time your friend measures. C You both measure the same amount of time
A The time you measure is longer than the time your friend measures. B
Could there be neutron stars that appear as pulsars to other civilizations but not to us? A Yes B No
A Yes
The Large Magellanic Cloud and Small Magellanic Cloud will probably A become part of the Milky Way. B remain orbiting forever. C become attached to another passing galaxy. D escape from the gravity of the Milky Way.
A become part of the Milky Way.
Astronomers detect dark matter A by comparing luminous mass to gravitational mass. B because it blocks background light. C because more distant galaxies move away faster. D because it emits lots of X-rays.
A by comparing luminous mass to gravitational mass.
Stars begin burning helium into carbon when the temperature reaches a critical value in the core. This temperature increase is caused by (choose all that apply) Multiple answers: You can select more than one option A gravitational collapse. B fusion of hydrogen into helium in the core. C fusion of hydrogen into helium in a shell around the core. D electron-degeneracy pressure.
A gravitational collapse. C fusion of hydrogen into helium in a shell around the core.
Astronomers determine the radius of an AGN by measuring A how much light comes from it. B how hard it pulls on stars nearby. C how quickly its light varies. D how quickly it rotates.
A how much light comes from it.
How does the energy production in a high-mass, main-sequence star differ from energy production in the Sun? (Choose all that apply.) Multiple answers: You can select more than one option A High-mass stars get a lot of energy through non-nuclear processes. B High-mass stars produce energy at a faster rate. C High-mass stars burn carbon on the main-sequence. D Stars use carbon in a process that fuses hydrogen to helium
B High-mass stars produce energy at a faster rate. D Stars use carbon in a process that fuses hydrogen to helium
Why does on-going star formation lead to a blue-white appearance? A There aren't any red or yellow stars. B Short-lived blue stars outshine the others. C Gas in the disk scatters blue light.
B Short-lived blue stars outshine the others.
According to the conservation of angular momentum, what would happen if a star orbiting in a direction opposite the neutron star's rotation fell onto a neutron star? A The neutron star's rotation would speed up. B The neutron star's rotation would slow down. C Nothing. The directions would cancel each other out.
B The neutron star's rotation would slow down.
One reason astronomers think neutron stars were formed in supernova explosions is that A all supernova remnants contain pulsars. B pulsars are made from heavy elements, such as those produced in supernova explosions. C pulsars spin very rapidly, as did the massive star just before it exploded. D pulsars sometimes have material around them that looks like the ejecta from supernova
B pulsars are made from heavy elements, such as those produced in supernova explosions.
If the main-sequence turnoff of a globular cluster occurs near the very top of the main sequence, then the cluster is A very old. B very young. C very hot. D very dense.
B very young.
Which of the following beams of light is moving the fastest? Choose one: A. a moving spaceship's "headlight" B. All of the beams are moving at c. C. a parked car's headlight D. a moving car's headlight
B. All of the beams are moving at c.
What causes a high-mass star to explode as a Type II supernova? Choose one: A. The high-mass star merges with another star. B. Iron absorbs energy when it fuses. C. The high-mass star runs out of mass in the core. D. The CNO cycle uses up all the carbon.
B. Iron absorbs energy when it fuses.
What happens when a star can no longer fuse hydrogen to helium in its core? A The core cools. B The core shrinks and heats up. C The core expands and heats up. D Helium fusion immediately begins.
B. The core shrinks and heats up.
Which parts of the Milky Way contain old stars, and which contain young stars? Choose one: A. The Milky Way galaxy only contains old stars. B. The disk contains young and old stars; the halo contains mostly old stars. C. The disk contains mostly young stars and the halo contains mostly old stars. D. The disk contains mostly old stars; the halo contains young and old stars.
B. The disk contains young and old stars; the halo contains mostly old stars.
How do two neutron stars get so close together? Choose one: A. Some other object has to intervene, pushing or pulling them close to each other. B. The orbital energy of the stars is lost in the form of gravity waves, allowing them to come close to each other. C. The orbital energy of the stars is lost in the form of radiation emitted from the poles, allowing them to come close to each other. D. Two neutron stars draw each other close by their intense gravity.
B. The orbital energy of the stars is lost in the form of gravity waves, allowing them to come close to each other.
The Hyashi track is a nearly vertical evolutionary track on the H-R diagram. What does the vertical nature of this track tell you about a protostar as it moves along it? Choose one: A. The star remains the same size. B. The star remains the same color. C. The star remains the same brightness. D. The star remains the same luminosity.
B. The star remains the same color.
Suppose that your friend flies past you in a spaceship, and both of you measure the time it takes the spaceship to pass your location. Which of the following statements is true for this scenario? Choose one: A. You both measure the same amount of time. B. The time you measure is longer than the time your friend measures. C. The time you measure is shorter than the time your friend measures.
B. The time you measure is longer than the time your friend measures.
According to Einstein's general theory of relativity, gravity is the Choose one: A. result of masses exerting a greater force at high speeds. B. result of the distortion in spacetime around a massive object. C. consequence of the relationship between mass and energy: E=mc2. D. consequence of length contraction.
B. result of the distortion in spacetime around a massive object.
If a black hole suddenly doubled in mass, the event horizon would become ___________ its original size. Choose one: A. one-half B. twice C. 4 times D. one-quarter E. 3 times
B. twice
What happens in a low-mass star when the core temperature rises enough for helium fusion to begin? (Hint: Degeneracy pressure is the main form of pressure in the inert helium core.) A Helium fusion slowly starts B Hydrogen fusion stops. C Helium fusion rises very sharply.
C Helium fusion rises very sharply.
Hubble's law was discovered using measurements of two properties of a galaxy: <blank1> and <blank2>. A size; mass B distance; rotational speed C distance; recession velocity D size; recession velocity
C distance; recession velocity
Supermassive black holes A are extremely rare - there are only a handful in the Universe. B are completely hypothetical. C occur in most, perhaps all, large galaxies. D occur only in the space between galaxies.
C occur in most, perhaps all, large galaxies.
Currently, stars form in A elliptical galaxies. B S0 galaxies. C spiral galaxies. D all of the above
C spiral galaxies.
Which property is detectable for both dark matter and the supermassive black hole at the center of the Milky Way A their luminosities B their temperatures C their gravity D their composition
C their gravity
If a black hole suddenly doubled in mass, the event horizon would become <blank> its original size. A one-quarter B one-half C twice D 3 times E 4 times
C twice
How does mass determine the main-sequence lifetime of a star? Choose one: A. More massive stars have different initial compositions than low-mass stars and thus have shorter lives. B. More massive stars burn different fuels than low-mass stars and thus have longer lives. C. More massive stars burn fuel faster than low-mass stars and thus have shorter lives. D. More massive stars have more fuel than low-mass stars and thus have longer lives.
C. More massive stars burn fuel faster than low-mass stars and thus have shorter lives.
What is at the very center of our galaxy? This question is difficult to answer because the center is completely obscured to our eyes behind a large amount of dust. On the basis of what you know about dust from previous chapters, what can be done to improve our view of the galaxy's center? Choose one: A. Observe it with a higher-resolution telescope. B. Calculate how much light has been absorbed by the dust and mathematically add it back into images of the center. C. Observe it in the infrared. D. Observe it with a blue filter. E. Observe it with a space telescope.
C. Observe it in the infrared.
Why do astronomers think that neutron stars were formed in supernova explosions? Choose one: A. A pulsar spins very rapidly, as did the massive star just before it exploded. B. Pulsars are made of heavy elements, such as those produced in supernova explosions. C. Pulsars sometimes have material around them that looks like the ejecta from supernovae. D. All supernova remnants contain pulsars.
C. Pulsars sometimes have material around them that looks like the ejecta from supernovae.
How do we know the Sun is not at the center of the Milky Way? Choose one: A. The Sun is moving toward the center of the Milky Way. B. There is no red- or blueshifted light from the stars. C. The Sun is not at the center of the globular-cluster distribution. D. The Sun is moving away from the center of the Milky Way.
C. The Sun is not at the center of the globular-cluster distribution.
Describe the path of the golf balls when they go directly toward the bowling ball. Choose one: A. They would immediately come to rest. B. They would follow a straight-line path. C. They would follow a curved path.
C. They would follow a curved path.
The best evidence for dark matter in the Milky Way comes from the observation that the rotation curve Choose one: A. falls off and then rises again. B. has a peak at about 2,000 light-years from the center. C. is quite flat at great distances from the center. D. rises swiftly in the interior.
C. is quite flat at great distances from the center.
A planetary nebula glows because Choose one: A. fusion is happening in the nebula. B. it is hot enough to emit UV radiation. C. light from the central star causes emission lines. D. it is heating up the interstellar medium around it.
C. light from the central star causes emission lines.
Based on what you have learned in previous chapters, which of the following measurements would we use to determine which galaxies are moving toward or away from the Milky Way? Choose one: A. the parallax angle of the galaxy B. the width of spectral lines within the galaxy's spectrum C. the Doppler shift of spectral lines within the galaxy's spectrum D. the total luminosity of the galaxy
C. the Doppler shift of spectral lines within the galaxy's spectrum
A molecular cloud fragments as it collapses because Choose one: A. the density increases fastest in the center of the cloud. B. the interstellar wind is stronger in some places than others. C. the rotation of the cloud throws some mass to the outer regions. D. density variations from place to place grow larger as the cloud collapses.
D
How do astronomers detect dark matter? Choose one: A. by determining how fast more distant galaxies recede B. by measuring the amount of X-rays emitted C. by measuring the amount of background light blocked D. by comparing luminous mass to gravitational mass
D
If the Sun instantaneously stopped giving off light, what would happen on Earth? Choose one: A. Earth would get dark 1 hour later. B. Earth would immediately get dark. C. Earth would get dark 27 minutes later. D. Earth would get dark 8 minutes later.
D
In astronomy, the term bipolar refers to outflows that Choose one: A. show spiral structure. B. alternate between expanding and collapsing. C. rotate about a polar axis. D. point in opposite directions.
D
Using the figure, determine which of the following statements accurately describes how fast each galaxy appears to be moving away from galaxy A. Choose one: A. Galaxies B, C, and D are all moving at the same speed away from galaxy A. B. Galaxies B and D are moving at the same speed away from galaxy A, but galaxy C is moving away more slowly. C. Galaxies B, C, and D are all moving at different speeds away from galaxy A. D. Galaxies B and D are moving at the same speed away from galaxy A, but galaxy C is moving away more quickly.
D
When you turn on a lightbulb in a room, the entire room appears to flood with light at the same time. Your eyes cannot perceive light originating at the bulb and then moving outward from it. This either means that light has infinite speed (appears everywhere instantaneously), or it moves so fast that it is difficult to tell the difference. How might you improve your chances of detecting the motion of light if it moves at finite speed? Choose one: A. change the color of the light source B. increase the brightness of the light source C. move closer to the light source D. move farther away from the light source
D
Which beam of light is moving faster? A the headlights of a parked car B the headlights of a moving car C the headlights of moving spaceship D all the beams are moving at c
D all the beams are moving at c
All the light in an AGN outburst travels A to the same destination. B at the same speed. C with the same frequency. D in the same direction.
D in the same direction.
How do astronomers detect dark matter? Choose one: A. by determining how fast more distant galaxies recede B. by measuring the amount of X-rays emitted C. by measuring the amount of background light blocked D. by comparing luminous mass to gravitational mass
D. by comparing luminous mass to gravitational mass
If a star follows a horizontal path across the H-R diagram, the star Choose one: A. maintains the same temperature. B. stays the same color. C. keeps the same spectral type. D. maintains the same luminosity.
D. maintains the same luminosity.
What property of these stars can we measure to determine how much mass is at the center of the galaxy? Choose one: A. their total luminosity B. their ages C. their average spectral type D. their velocities as they orbit the center
D. their velocities as they orbit the center
The cosmological principle states that Choose one: A. our place in the universe is not special. B. our universe is infinite. C. the rules governing matter and energy are different from place to place. D. we are at the center of the universe.
a
The scientific method is a process by which scientists A gain confidence in theories by failing to prove them wrong. B survey what the majority of people think about a theory. C prove theories to be known facts. D show all theories to be wrong.
a
its outer layers, which expand into a planetary nebula, as shown in the image on the right. At the center, the very dense carbon-ash core of the star is left behind: a white dwarf. The image on the left shows the path the star takes on the H-R diagram as it sheds its outer layers and settles down as a white dwarf, which has no fuel left to burn. Based on the white dwarf's position in the H-R diagram, which of the following statements is true? Choose one: A. White dwarfs are fainter than stars in other stages at the same temperature because they are smaller. B. White dwarfs are brighter than stars in other stages because carbon fusion outputs more energy than hydrogen and helium fusion. C. White dwarfs are brighter than stars in other stages because they are hotter. D. White dwarfs are fainter than stars in other stages because they are hotter.
a
How does the energy production in a high-mass, main-sequence star differ from energy production in the Sun? Choose one or more: A. High-mass stars use carbon in a process that fuses hydrogen to helium. B. High-mass stars produce energy at a faster rate. C. High-mass stars burn carbon on the main sequence. D. High-mass stars get a lot of energy through non-nuclear processes.
a and B
The Big Bang theory predicted Choose one or more: A. the abundance of helium. B. the period-luminosity relation of Cepheid variables. C. that the sky should be dark at night. D. Hubble's law. E. the cosmic microwave background radiation. F. the cosmological principle.
a, e
In order for an electron to jump up two energy levels in an atom at once, it requires (choose one or more) A a bluer photon than to jump up one energy level. B a precise amount of energy. C any amount of energy. D more energy than to jump up one energy level.
all except c
The majority of stars, including the Sun, are on the main sequence. The masses and sizes of main-sequence stars in the H-R diagram are indicated in this figure.Study how the various properties of a main-sequence star are related to one another in the figure. Then select the properties in the list that would increase if the mass of a main-sequence star is increased. Choose one or more: A. luminosity B. temperature C. radius
all three
According to Einstein's general theory of relativity, gravity is the Choose one: A. result of masses exerting a greater force at high speeds. B. result of the distortion in spacetime around a massive object. C. consequence of the relationship between mass and energy: E=mc2. D. consequence of length contraction.
b
From your observations of these spectra, which wavelengths would be best to observe objects in order to get a view that is the least obstructed by interstellar extinction? Choose one: A. the shortest wavelengths possible B. the longest wavelengths possible C. a window in the midrange of wavelengths, around the color green D. at very specific wavelengths throughout the entire spectrum where dust does not absorb light, depending on its composition
b
How do two neutron stars get so close together? Choose one: A. Some other object has to intervene, pushing or pulling them close to each other. B. The orbital energy of the stars is lost in the form of gravity waves, allowing them to come close to each other. C. The orbital energy of the stars is lost in the form of radiation emitted from the poles, allowing them to come close to each other. D. Two neutron stars draw each other close by their intense gravity.
b
How does the spectrum of a distant star reveal the star's chemical composition? Choose one: A. The total energy of light received from a star, as determined by its spectrum, is directly related to its chemical composition. B. Dark lines, also called absorption lines, within the spectra are "fingerprints" for the different atoms and molecules within a star's atmosphere. C. The type of light that is being produced the most within the spectrum of a star is directly related to its chemical composition. D. The chemical composition of a star determines how bright the star appears to be and, in turn, how much of the spectrum is received.
b
How would the light we observe on Earth from a high-redshift galaxy compare to the light observed from a low-redshift galaxy? Choose one: A. We will see the high- and low-redshift galaxies the way they both were at the same time in the distant past. B. We will see the high-redshift galaxy as it was earlier in time than the low-redshift galaxy. C. We will see the low-redshift galaxy as it was earlier in time than the high-redshift galaxy. D. We will see the high- and low-redshift galaxies the way they both are right now.
b
If a black hole suddenly doubled in mass, the event horizon would become ___________ its original size. Choose one: A. one-half B. twice C. 4 times D. one-quarter E. 3 times
b
If the speed of light must be constant for all observers (3 × 108 meters per second), regardless of point of view, and Speed = Distance traveled/Time (v = d/t), what must be true about the light pulse in the image here?Choose one: A. The time for the light pulse to travel from the lamp to the detector is the same for both observers. B. The time for the light pulse to travel from the lamp to the detector is less for observer 1. C. The time for the light pulse to travel from the lamp to the detector is less for observer 2.
b
Suppose that your friend flies past you in a spaceship, and both of you measure the time it takes the spaceship to pass your location. Which of the following statements is true for this scenario? Choose one: A. You both measure the same amount of time. B. The time you measure is longer than the time your friend measures. C. The time you measure is shorter than the time your friend measures.
b
The higher the photon energy, A the longer its wavelength. B the shorter its wavelength. C energy is independent of wavelengh
b
When an object is farther away, it appears to move _____ against the background than a closer object. Choose one: A. more B. less
b
Which of the following beams of light is moving the fastest? Choose one: A. a moving spaceship's "headlight" B. All of the beams are moving at c. C. a parked car's headlight D. a moving car's headlight
b
Which parts of the Milky Way contain old stars, and which contain young stars? Choose one: A. The Milky Way galaxy only contains old stars. B. The disk contains young and old stars; the halo contains mostly old stars. C. The disk contains mostly young stars and the halo contains mostly old stars. D. The disk contains mostly old stars; the halo contains young and old stars.
b
A star's size is determined by the relative strength of forces attempting to make it collapse and forces attempting to make it expand. The balance between gravity and pressure causes a star to retain a roughly constant size throughout its main-sequence lifetime. When it runs out of hydrogen and nuclear fusion stops in the core, the pressure drops and the star collapses. Based on this and the descriptions in the figure, why does it then expand in size during the red giant phase? Choose one: A. It is gaining mass as it engulfs the planets surrounding it. B. A star can only collapse so far: it rebounds after hitting the limit and its momentum causes it to expand outward. C. The hydrogen shell burning is producing more total energy than the core hydrogen burning did. D. It is losing mass, so its self-gravity is weaker.
c
Based on what you have learned in previous chapters, which of the following measurements would we use to determine which galaxies are moving toward or away from the Milky Way? Choose one: A. the parallax angle of the galaxy B. the width of spectral lines within the galaxy's spectrum C. the Doppler shift of spectral lines within the galaxy's spectrum D. the total luminosity of the galaxy
c
Based purely on your observations of this plot, which of the following statements best describes the visible distribution of mass within that galaxy? Choose one: A. The lowest concentration of mass is in the center of the galaxy, and it increases with increasing distance from the center. B. The vast majority of the galaxy's mass is concentrated in a tiny region in its center, with mostly empty space outside of that region. C. The highest concentration of mass is in the center of the galaxy, and it decreases with increasing distance from the center. D. It is impossible to say, as mass has nothing to do with the intensity of light.
c
Describe the path of the golf balls when they go directly toward the bowling ball. Choose one: A. They would immediately come to rest. B. They would follow a straight-line path. C. They would follow a curved path.
c
How do we know the Sun is not at the center of the Milky Way? Choose one: A. The Sun is moving toward the center of the Milky Way. B. There is no red- or blueshifted light from the stars. C. The Sun is not at the center of the globular-cluster distribution. D. The Sun is moving away from the center of the Milky Way.
c
How does mass determine the main-sequence lifetime of a star? Choose one: A. More massive stars have different initial compositions than low-mass stars and thus have shorter lives. B. More massive stars burn different fuels than low-mass stars and thus have longer lives. C. More massive stars burn fuel faster than low-mass stars and thus have shorter lives. D. More massive stars have more fuel than low-mass stars and thus have longer lives.
c
How does the spectrum of a distant star reveal the star's chemical composition? A The chemical composition of a star determines how bright the star appears to be and, in turn, how much of the spectrum is received. B The total energy of light received from a star, as determined by its spectrum, is directly related to its chemical composition. C Dark lines, also called absorption lines, within the spectra are "fingerprints" for the dierent atoms and molecules within a star's atmosphere. D The type of light that is being produced the most within the spectrum of a star is directly related to its chemical composition.
c
The best evidence for dark matter in the Milky Way comes from the observation that the rotation curve Choose one: A. falls off and then rises again. B. has a peak at about 2,000 light-years from the center. C. is quite flat at great distances from the center. D. rises swiftly in the interior.
c
The cosmological principle states that A the Universe is expanding in all directions at the same rate. B a unique center of the Universe exists. C the Universe looks the same everywhere and in all directions as long as you look on large enough spatial scales. D physical laws change from place to place in the Universe. E the Universe is in a "steady state" .
c
What effect would you expect this to have on stars? Choose one: A. There will be an equal amount of star formation everywhere, but stellar lifetimes will be shorter in between the spiral arms. B. There will be an equal amount of star formation everywhere, but stellar lifetimes will be shorter inside the spiral arms. C. There will be more star formation inside the spiral arms. D. There will be more star formation in between the spiral arms.
c
What is at the very center of our galaxy? This question is difficult to answer because the center is completely obscured to our eyes behind a large amount of dust. On the basis of what you know about dust from previous chapters, what can be done to improve our view of the galaxy's center? Choose one: A. Observe it with a higher-resolution telescope. B. Calculate how much light has been absorbed by the dust and mathematically add it back into images of the center. C. Observe it in the infrared. D. Observe it with a blue filter. E. Observe it with a space telescope.
c
Why do astronomers think that neutron stars were formed in supernova explosions? Choose one: A. A pulsar spins very rapidly, as did the massive star just before it exploded. B. Pulsars are made of heavy elements, such as those produced in supernova explosions. C. Pulsars sometimes have material around them that looks like the ejecta from supernovae. D. All supernova remnants contain pulsars.
c
Which of the following was not created as a result of Big Bang nucleosynthesis? Choose one or more: lithium carbon deuterium oxygen iron
carbon, oxygen, iron
If a star follows a horizontal path across the H-R diagram, the star Choose one: A. maintains the same temperature. B. stays the same color. C. keeps the same spectral type. D. maintains the same luminosity.
d
In this representation, why are the paper clips getting farther apart with time? Choose one: A. Each paper clip is moving the rubber band away from one another. B. The entire rubber band is moving through space. C. The size of the paper clips is shrinking. D. The rubber band is stretching between them.
d
The cosmological principle says that Choose one: A. the universe began in the Big Bang. B. the universe is expanding. C. All answer options are correct. D. the rules that govern the universe are the same everywhere.
d
The simplest way to estimate the age of the universe is from Choose one: A. models of stellar evolution. B. measurements of the abundances of elements. C. the age of Moon rocks. D. the slope of the Hubble constant.
d
What property of these stars can we measure to determine how much mass is at the center of the galaxy? Choose one: A. their total luminosity B. their ages C. their average spectral type D. their velocities as they orbit the center
d
What happens when the star's core runs out of helium? A The star explodes. B Carbon fusion begins. C The core cools off. D Helium fuses in a shell around the core.
d. Helium fuses in a shell around the core.
Hubble's law was discovered using measurements of two properties of a galaxy: _______ and _______. Choose one: distance; rotation speed size; mass distance; recession velocity size; recession velocity
distance recession velocity
Hubble's law was discovered using measurements of two properties of a galaxy: _______ and _______. Choose one: distance; rotation speed size; mass distance; recession velocity size; recession velocity
distance; recession velocity
a star remains on the main sequences as long as......
it can fuse hydrogen into helium in its core
We will now specifically consider low-mass stars such as the Sun, which have masses less than 3 solar masses. As the star collapses, it becomes denser and hotter, until the layer just outside the helium ash core reaches the temperatures necessary to burn hydrogen (10 million K). The star moves off the main sequence and enters the next phase in its life, where it is now fusing hydrogen into helium in a shell surrounding a core of nonburning helium. The red line on the H-R diagram here shows the "red giant branch," and describes how the star changes (following the white arrow) as it moves away from the main sequence during this phase. Based on your observations of this diagram, choose all the statements that correctly describe what is happening to the star during this time. Choose one or more: A. The star is getting fainter. B. The star is getting larger. C. The star is getting redder. D. The star's surface is getting hotter.
larger, redder
the life of a main sequence star depends on its _________
mass
mass transfer
material can flow from the giant star to the companion
our knowledge of the life stories of stars comes from comparing....?
mathematical models of stars with observations
main sequence lifetime
the amount of time that a star spends on the main sequence, burning hydrogen as its primary source of energy
thermal once the star has used up the hydrogen in the innermost core, ____________ leaks out of the helium core into the surrounding layers of the star, but no more energy is generated within the core to replace it
thermal energy
star clusters are particularly useful because....?
they contain stars of different mass that were born about the same time
17.1 How does energy production in a high-mass, main-sequence star differ from energy production in the Sun? (Choose all that apply.) ⓐ High-mass stars get a lot of energy through non-nuclear processes. ⓑ High-mass stars produce energy at a faster rate. ⓒ High-mass stars burn carbon on the main sequence. ⓓ High-mass stars use carbon in a process that fuses hydrogen to helium
ⓑ High-mass stars produce energy at a faster rate. ⓓ High-mass stars use carbon in a process that fuses hydrogen to helium
17.2 What causes a high-mass star to explode as a Type II supernova? ⓐ The high-mass star merges with another star. ⓑ Iron absorbs energy when it fuses. ⓒ The high-mass star runs out of mass in the core. ⓓ The CNO cycle uses up all the carbon.
ⓑ Iron absorbs energy when it fuses.
17.3 One reason astronomers think neutron stars were formed in supernova explosions is that: ⓐ all supernova remnants contain pulsars; ⓑ pulsars are made of heavy elements, such as those produced in supernova explosions; ⓒ pulsars spin very rapidly, as did the massive star just before it exploded; ⓓ pulsars sometimes have material around them that looks like the ejecta from supernovae.
ⓑ pulsars are made of heavy elements, such as those produced in supernova explosions;
20.3 Which property is detectable for both dark matter and the supermassive black hole at the center of the Milky Way? ⓐ their luminosities ⓑ their temperatures ⓒ their gravity ⓓ their composition
ⓒ their gravity