astronomy set 3

Collisions between galaxies a. occur only very occasionally to produce spectacular supergalaxies containing many new stars. Only one or two examples have been detected so far. b. are occurring all the time, all elliptical galaxies having resulted from such collisions. The collisions have cleared out all the gas and dust from these galaxies. c. never happen since galaxies are so far apart in our universe. d. can and do occur relatively frequently over cosmological times.

NOT: a. occur only very occasionally to produce spectacular supergalaxies containing many new stars. Only one or two examples have been detected so far.

The Crab Nebula is a nearby example of what type of physical phenomenon? a. planetary nebula, a shell of gas leaving an old star b. remnant of a supernova explosion c. spiral galaxy, a collection of 100 billion stars d. gas and dust cloud, the formation region for new stars

NOT: a. planetary nebula, a shell of gas leaving an old star

If the Sun were to be at or close to the galactic center of the Milky Way, the intensity of starlight in the nighttime sky on Earth would be a. very much fainter than at present because neighboring stars would be obscured by dense dust and gas clouds. b. about the same as it is now since neighboring stars would still be relatively far away. c. about twice as bright as at present since neighboring stars would be mostly bright, young blue stars in about the same numbers as the present, older, and less bright red giant neighbors to the Sun. d. extremely intense from the dense field of stars, equivalent to about 200 full Moons.

NOT: a. very much fainter than at present because neighboring stars would be obscured by dense dust and gas clouds.

A Cepheid variable star with a pulsation period of a few days is seen in the spiral arm of a galaxy. Its apparent brightness is measured as 104 times fainter than an equivalent star 1000 ly away from the Sun in the Milky Way Galaxy. Assuming no light absorption between galaxies, what is the distance to the far Cepheid and hence to the galaxy? a. 107 ly (104 times farther away) b. 10,000 ly (10 times farther away) c. 10 ly (100 times closer) d. 100,000 ly (100 times farther away)

NOT: b. 10,000 ly (10 times farther away)

What is the difference between a normal pulsar, which emits radiation in the radio range, and a pulsating X-ray source? a. A pulsating X-ray source combines the characteristics of an ordinary pulsar and a variable star. The surface pulsates in and out creating a pulsating source. b. A pulsating X-ray source is a binary system of two pulsars in very rapid rotation around one another. We see the interference pattern of the two pulsar beams as a pulsating X-ray jet. c. A pulsating X-ray source is an ordinary pulsar, but occasionally, when the neutron star experiences a glitch and the crust cracks, the hot interior is exposed and emits an intense beam of X rays. d. A pulsating X-ray source is a pulsar with a binary companion. Matter pulled off the companion spirals along the intense magnetic field of the pulsar, and its interaction with the surface produces X-ray jets.

NOT: b. A pulsating X-ray source is a binary system of two pulsars in very rapid rotation around one another. We see the interference pattern of the two pulsar beams as a pulsating X-ray jet.

What designation do we give to the first stars? a. Population 0 b. Population I c. Population II d. Population III

NOT: b. Population I

In the unified model of active galaxies, the main difference among quasars, BL Lacertae objects, and radio galaxies appears to be that a. we see the accretion disk around the central black hole from a different angle in each case—face-on for BL Lacertae, edge-on for radio galaxies, and in between for quasars. b. the rate at which matter is falling into the central black hole is different in each case—largest in quasars, less in BL Lacertae objects, and least in radio galaxies. c. the mass of the central black hole is different in each case—largest in quasars, less in BL Lacertae, and least in radio galaxies. d. the galaxy type with which they are associated is different in each case—spiral for BL Lacertae, elliptical for quasars, and irregular for radio galaxies.

NOT: b. the rate at which matter is falling into the central black hole is different in each case—largest in quasars, less in BL Lacertae objects, and least in radio galaxies.

If the cosmological constant exists, what physical effect is believed to create it? a. New matter is constantly being created in the expanding voids between superclusters of galaxies, and the energy released by this creation accelerates the expansion of the universe. b. No one knows. The cosmological constant has been hypothesized to exist because we see the universal expansion accelerating, but its source is still a mystery. c. Energy released by nuclear reactions in stars and then emitted into space is heating the universe and accelerating its expansion. d. Virtual particles that constantly appear and disappear add energy to empty space, and this vacuum energy provides a constant repulsive force that accelerates the universe.

NOT: c. Energy released by nuclear reactions in stars and then emitted into space is heating the universe and accelerating its expansion.

The Scorpius-Centaurus OB association is predicted to have produced a supernova about 2 million years ago. What led to this prediction? a. A supernova remnant with the appropriate location and age was found. b. O and B stars are massive stars, many of them over 25 solar masses, and they would supernova. c. In a close association, collisions between stars are expected, and collisions would raise the mass to the supernova range. d. Shock waves from the direction of Scorpius-Centaurus still pass by Earth at frequent intervals.

NOT: c. In a close association, collisions between stars are expected, and collisions would raise the mass to the supernova range.

If the elliptical galaxy in Boötes, shown at the bottom of Figure 16-31 in Comins and Kaufmann, Discovering the Universe, 8th ed., were at a distance of 1.6 billion ly, what would be an upper limit to the age of the universe? (Be careful with units.) a. 0.47 billion years b. 12 million years c. 47 billion years d. 12 billion years

NOT: a. 0.47 billion years

The existence of stars composed almost entirely of neutrons was first predicted by a. Jocelyn Bell in 1967. b. Stephen Hawking in 1985. c. Fritz Zwicky and Walter Baade in 1933. d. Albert Einstein in 1908.

NOT: a. Jocelyn Bell in 1967.

What is the Hubble classification for a spiral galaxy with a small nuclear region and loosely wound arms? a. Sa b. Sc c. SBa d. Sb

NOT: a. Sa

During its life, a massive star creates heavier and heavier elements in its core through thermonuclear fusion, leading up to silicon and iron. What is the fate of the iron that is created? a. The nuclei are split apart by neutron bombardment, creating lighter elements such as carbon, oxygen, and neon. b. The iron is locked up inside the star forever. c. The iron is destroyed by later thermonuclear fusion reactions in the core that create even heavier elements such as lead, gold, and uranium. d. The iron is torn apart by high-energy photons at the end of the star's life.

NOT: a. The nuclei are split apart by neutron bombardment, creating lighter elements such as carbon, oxygen, and neon.

In the approximately 5 billion years since the Sun began its main-sequence phase, its radius has increased by 6% and its surface temperature has increased by 5%. How has its luminosity changed? a. decreased by 10% b. decreased by 5% c. increased by 37% d. increased by 43%

NOT: a. decreased by 10%

One of the "quiet" bands in the electromagnetic spectrum used for SETI is the so-called "water hole" between about 103 and 104 MHz. What is the principal source of the natural signals in this frequency band? a. emissions from the water molecule b. emissions from oxygen molecules c. osmic microwave background radiation d. radio emission from terrestrial sources

NOT: a. emissions from the water molecule

What is microlensing? a. minute shift in the apparent position of a star as an object passes in front of it b. slow brightening of a star as an object passes in front of it c. temporary disappearance of a star as an object passes in front of it d. gradual reduction in brightness of a star as an object passes in front of it

NOT: a. minute shift in the apparent position of a star as an object passes in front of it

A red filter passes light at the long-wavelength end of the visible spectrum as shown, for example, in Figure 11-4 in Comins and Kaufmann, Discovering the Universe, 8th ed. Star 1 and star 2 are viewed through identical red filters, and star 1 appears brighter than star 2 through the filter. What can be determined from this information? a. Star 1 is hotter than star 2. b. Star 2 is hotter than star 1. c. Star 1 is more luminous than star 2. d. Nothing can be concluded from this fact alone.

NOT: c. Star 1 is more luminous than star 2.

How many times brighter is a star with an apparent magnitude of +1.0 than a star with an apparent magnitude of +6.0? a. 100 times brighter b. 5 times brighter c. The question is incorrectly worded; the magnitude +6 star will be 100 times brighter than the magnitude +1 star. d. 2.512 times brighter.

NOT: c. The question is incorrectly worded; the magnitude +6 star will be 100 times brighter than the magnitude +1 star.

The Hubble distance-velocity relation states that a. all objects appear to have the same velocity away from the Sun, regardless of distance from the Sun. b. mutual gravitational attraction of all objects in the universe means that all objects appear to be moving toward the Sun, the closest ones traveling fastest. c. all distant objects are moving toward the Sun, the most distant objects fastest. d. the farther an object is from the Sun, the faster it appears to be moving away from the Sun.

NOT: c. all distant objects are moving toward the Sun, the most distant objects fastest.

The shape of the cross-section of the Roche lobes around a close binary star system, taken through the centers of both stars, is a. two unequal ellipses that touch at the center of the lobes. b. a sphere centered on the center of mass of the star system. c. an ellipse with a star at each focus. d. a figure eight.

NOT: c. an ellipse with a star at each focus.

The Andromeda Galaxy (M31) is best described as a(n) a. extension of the Milky Way. b. vortex surrounding a black hole. c. gaseous nebula extending for 6° across our sky. d. spiral collection of stars, dust, and gas 2 million ly away.

NOT: c. gaseous nebula extending for 6° across our sky.

The Milky Way, the galaxy in which the Sun resides, is an example of which type of galaxy? a. spiral (a regular pattern of spiral arms) b. elliptical (a smooth star distribution lacking spiral arms) c. The Milky Way is not a galaxy at all but a large cluster of stars. d. irregular (possible clumps of stars but no overall pattern)

a. spiral (a regular pattern of spiral arms)

What is the Pauli exclusion principle? a. Photons of less than a certain wavelength cannot eject electrons from a metal. b. Two identical particles cannot occupy the same place at the same time. c. Two different atoms cannot have the same energy levels. d. Two identical photons cannot be absorbed by the same atom.

b. Two identical particles cannot occupy the same place at the same time.

BL Lacertae objects appear to be a. giant irregular galaxies with neither spiral arms nor the smooth shape of elliptical galaxies. b. elliptical galaxies with bright, starlike nuclei. c. spiral galaxies with bright, starlike nuclei. d. active galaxies, most of whose energy is emitted by two widely spaced radio lobes.

b. elliptical galaxies with bright, starlike nuclei.

Suppose a satellite were placed in orbit around (and very close to) a neutron star. Which theory would you need to use to describe how it moves? a. special theory of relativity b. general theory of relativity c, Kepler's laws d. Newton's law of gravitation

b. general theory of relativity

Using the Hertzsprung-Russell diagram (Figure 11-7 of Comins and Kaufmann, Discovering the Universe, 8th ed.), determine which type of star has the following characteristics: surface temperature of 40,000 K, luminosity 100,000 times that of the Sun. a. cool, red, main-sequence star b. hot, blue, main-sequence star c. white dwarf d. red giant

b. hot, blue, main-sequence star

The process of evolution of stars in our universe has been interpreted by a. matching theoretical models to the properties of similar stars at different distances from Earth since we are seeing more distant stars at an earlier time, when the light left them. b. matching theoretical models to the collective properties, such as luminosity, temperature, and size, of millions of stars as we see them. c. designing theoretical models solely on the basis of the known properties of matter, without reference to observational data on real stars, since we do not have a sufficiently long time base for stellar observations. d. matching theoretical models to the detailed observation of a few stars as we watch them change in luminosity, temperature, and size during their evolution.

b. matching theoretical models to the collective properties, such as luminosity, temperature, and size, of millions of stars as we see them.

Which of the following astronomical objects is most closely associated with a pulsar? a. red giant star b. neutron star c. black hole d. white dwarf star

b. neutron star

Harlow Shapley first located the center of the Milky Way Galaxy in 1917 by a. measuring the positions of supernova explosions throughout the Galaxy. b. observing the distribution of globular clusters in the galactic halo. c. measuring redshifts of stars in the galactic plane and disk. d. observing the distribution of hydrogen gas, measured by 21-cm radio emission.

b. observing the distribution of globular clusters in the galactic halo.

The primary evidence for the expanding universe concept is the a. slow spreading out of stars in the near neighborhood of the Sun. b. redshift of light from distant galaxies, which increases with distance of the galaxy from Earth. c. discovery of black holes in binary stars. d. slow increase in the Earth-Moon separation—about 4 cm per year—with time.

b. redshift of light from distant galaxies, which increases with distance of the galaxy from Earth.

A white dwarf is a(n) a. object like Jupiter that was not quite massive enough to become a star. b. small, very hot, low-mass star. c. type of small protostar. d. hot, main-sequence star.

b. small, very hot, low-mass star.

The fact that matter exists today is evidence that matter particles outnumber antimatter particles in the universe. This imbalance was caused by a. matter inflation. b. symmetry breaking. c. chirality. d. the cosmic overshift.

b. symmetry breaking.

If we compare an elliptical galaxy and a spiral galaxy of the same mass a billion years after both began formation, a. they should each have about the same number of stars. b. the elliptical galaxy will have formed more stars than the spiral. c. the spiral galaxy will have formed more stars than the elliptical. d. neither galaxy will have formed any stars during the first billion years.

b. the elliptical galaxy will have formed more stars than the spiral.

Cepheid variable stars are invaluable in astronomy because of the close relationship between a. the peak wavelength of their spectra and their surface temperatures. b. their luminosity, or absolute magnitude, and their pulsation period. c. the redshift of their spectra and their distance from the Sun. d. their apparent magnitude and their pulsation period.

b. their luminosity, or absolute magnitude, and their pulsation period.

The fact that quasars can be detected from distances from which even the biggest and most luminous galaxies cannot be seen means that a. they must be in directions where gravitational focusing by the masses of nearer galaxies makes them visible from Earth. b. they must be far more luminous than the brightest galaxies. c. they must be in directions where intergalactic absorption by dark matter is minimum, allowing us to see them. d. their spectra have not been as redshifted by their motion as those of galaxies and hence they can still be seen.

b. they must be far more luminous than the brightest galaxies.

Which is the correct sequence for the end points of stellar evolution, in order of increasing mass? a. white dwarf, black hole, neutron star b. white dwarf, neutron star, black hole c. neutron star, black hole, white dwarf d. black hole, neutron star, white dwarf

b. white dwarf, neutron star, black hole

Quasars are a. sources of great energy, very large in actual size, and shaped like galaxies. b. sources of intense radio energy only, not visible at other wavelengths, and relatively large but very distant. c. prolific sources of energy, starlike in appearance, and intrinsically small. d. starlike sources of great energy located in the Milky Way Galaxy and intrinsically very small.

c. prolific sources of energy, starlike in appearance, and intrinsically small.

The puzzle about quasar spectra, which was finally solved by Maarten Schmidt, was a. that the characteristic pattern of hydrogen spectral lines was seen but at much greater blueshifts than is usual from hydrogen in stellar sources. b. that the brightnesses of hydrogen lines in the familiar spectral sequence were seen to fluctuate wildly over times of seconds from such a bright and therefore presumably large object. c. that the characteristic pattern of hydrogen spectral lines was seen but at much greater redshifts than is usual from hydrogen in stellar sources. d. that a familiar spectral line sequence of hydrogen lines was detected from these starlike objects, but they had intensity ratios between lines radically different from those seen in spectra from nearby stars.

c. that the characteristic pattern of hydrogen spectral lines was seen but at much greater redshifts than is usual from hydrogen in stellar sources.

It is unlikely that intelligent life would develop on a planet circling a star of significantly less mass than the Sun because a. no Moon would form around a planet near such a star, and a Moon is considered to have been essential for the evolution of life because of tidal variations on Earth. b. the lifetime of such a star on the main sequence is too short; life-forms on such a planet would not have time to evolve intelligence. c. the planet would probably become tidally locked to the star, making one side of the planet too hot and the other side too cold. d. there would be no region around the star where UV, visible, and IR light intensities would be suitable for the evolution of life.

c. the planet would probably become tidally locked to the star, making one side of the planet too hot and the other side too cold.

One of the big puzzles about the properties and behavior of large clusters of galaxies is that a. each cluster appears to consist of the same type of galaxy, some made up totally of spiral galaxies while others contain only ellipticals. b. they appear to be spread uniformly throughout space in all directions, which is difficult to explain with the Big Bang theory. c. there appears to be insufficient mass in the luminous matter (stars, and so on) to hold the cluster together gravitationally. d. they appear not to take part in the general expansion of the universe, in contrast to single separate galaxies, probably because they are gravitationally bound to one another.

c. there appears to be insufficient mass in the luminous matter (stars, and so on) to hold the cluster together gravitationally.

The radial velocity curve of a star in a binary star system is a plot against time of the a. speed of the star in a direction perpendicular to the line of sight to the star. b. position of the star in celestial coordinates. c. variation of Doppler shift of the star's spectral lines and hence of its speed toward or away from us. d. temperature of the star as determined from the movement of the peak wavelength of its spectrum.

c. variation of Doppler shift of the star's spectral lines and hence of its speed toward or away from us.

Compared with the composition of the early Sun, the composition of the gas at the core of a star that has just become a red giant is a. very different since thermonuclear fusion has transformed all the hydrogen and helium into heavier elements. b. very different; there is lots of hydrogen but almost no helium left after thermonuclear fusion. c. very different since thermonuclear fusion has transformed all the hydrogen into helium. d. the same, with a higher fraction of hydrogen than helium since these stars were produced with the same initial material.

c. very different since thermonuclear fusion has transformed all the hydrogen into helium.

The stars that last longest are the stars a. with the largest luminosity and highest temperature since they take the longest to cool down to invisibility. b. with the largest mass, that is, the largest amount of fuel. c. with the smallest mass. d. of intermediate mass; small-mass stars have little fuel and burn out quickly, while very massive stars burn their fuel very rapidly.

c. with the smallest mass.

How bright (in absolute magnitude) are the intrinsically brightest stars in the universe? a. +17 b. +1 c. 0 d. -10

d. -10

According to Hubble's law, how old is the universe (H0 = Hubble's constant)? a. v/H0 (where v = recession velocity in km/s) b. r/H0 (where r = distance in Mpc) c. H0 d. 1/H0

d. 1/H0

What would the mass of a primordial black hole need to have been for it to be just disappearing now due to the loss of Hawking radiation? a. 10 kg b. 10 million kg c. 10,000 kg d. 10 billion kg

d. 10 billion kg

What is the typical temperature of the intergalactic gas in rich clusters of galaxies? a. 10,000 to 20,000 K b. 1 to 10 billion K c. 10 to 100 K d. 10 to 100 million K

d. 10 to 100 million K

What will be the intrinsic brightness or luminosity of a white dwarf star that has the same temperature as the Sun? (See Figure 11-7, Comins and Kaufmann, Discovering the Universe, 8th ed.) a. 4 times the Sun's luminosity b. Because it has the same surface temperature, the white dwarf will have the same brightness. c. 10-2 of the Sun's luminosity d. 10-4 of the Sun's luminosity

d. 10-4 of the Sun's luminosity

Suppose an astronomer discovers a distant quasar whose recessional velocity is 1/3 the speed of light. If Hubble's constant is 50 km/s per Mpc, how far away is the quasar? a. 5 million Mpc b. 200 Mpc c. 50 Mpc d. 2000 Mpc

d. 2000 Mpc

Why is it that we will not see fluctuations in light output in times shorter than about 1 day when we observe an extragalactic source whose diameter is about 1 light-day? a. Absorption of light by intergalactic matter will smooth out rapid fluctuations within the beam. b. The light from different parts of the source will be Doppler-shifted by different amounts, allowing us to see only an average shift. c. It is inconceivable that a source of this size could vary on such short time scales. d. Arrival times will be different from different parts of the source, which will smooth out short-term fluctuations.

d. Arrival times will be different from different parts of the source, which will smooth out short-term fluctuations.

Probably the most difficult factor to estimate in the Drake Equation is a. R*, the rate at which solar-type stars form in the Galaxy. b. fp, the fraction of stars that have planets. c. ne, the number of planets per solar system that are Earthlike (suitable for life). d. L, the lifetime of a technologically advanced civilization.

d. L, the lifetime of a technologically advanced civilization.

What is the evidence that indicates to some astronomers that a supermassive black hole exists at the center of the Milky Way Galaxy? a. A Doppler shift of light from stars in the near neighborhood of the galactic center indicates that the stars are falling inward at very high speeds. c. The Sun's motion in space shows that, if Kepler's law holds for its orbit around the galactic center, there must be a very massive object at the center of the Milky Way. c. No electromagnetic radiation at all comes from the precise position of the galactic center, and it just looks like a dark void in space. d. Measurement of gas clouds orbiting the galactic center at very high speeds indicates that they would rapidly move out of the Galaxy unless some very massive object were holding them in orbit.

d. Measurement of gas clouds orbiting the galactic center at very high speeds indicates that they would rapidly move out of the Galaxy unless some very massive object were holding them in orbit.

Observationally, the biggest difference between quasars and other active galaxies such as Seyfert and radio galaxies appears to be that (see Table 17-1, Comins and Kaufmann, Discovering the Universe, 8th ed.) a. quasars appear to be located inside elliptical galaxies, whereas b. Seyfert and radio galaxies are spirals. Seyfert and radio galaxies do not have the bright, starlike nuclei of quasars. c. the brightness of Seyfert and radio galaxies does not vary with time. d. Seyfert and radio galaxies are less powerful energy emitters than quasars.

d. Seyfert and radio galaxies are less powerful energy emitters than quasars.

Long-exposure color photographs of the night sky often show regions that glow red, such as the Rosette Nebula in Figure 12-8 of Comins and Kaufmann, Discovering the Universe, 8th ed. This distinctive red color is caused by the a. emission of red and infrared light by warm dust grains. b. collective glow of many red giant stars in the region. c. scattering of starlight by dust grains in the nebula. d. ionization and subsequent recombination of hydrogen atoms.

d. ionization and subsequent recombination of hydrogen atoms.

Recent results from very bright supernovae in very distant galaxies seem to indicate that the expansion of the universe a. has now stopped and the universe will shortly begin to contract again toward a Big Crunch. b. is decelerating (slowing down). c. is continuing at a constant rate and has done so since just after the Big Bang. d. is accelerating (speeding up).

d. is accelerating (speeding up).

A rich, regular cluster of galaxies differs from a rich, irregular cluster in that a. its galaxies are distributed in a regular, highly flattened system (like a disk). b. it contains fewer galaxies than does an irregular cluster. c. it lacks the giant elliptical galaxies often found in irregular clusters. d. it has fewer spirals and more ellipticals and S0 galaxies than an irregular cluster.

d. it has fewer spirals and more ellipticals and S0 galaxies than an irregular cluster.

The discovery of the peculiar galaxy Cygnus A was a surprise to astronomers because a. the redshift of its radio wavelength signal was as high as anything measured up to that time. b. it was first discovered at X-ray wavelengths and detected at optical and radio wavelengths only some time later. c. it was so bright at optical wavelengths that no one expected it to be a galaxy. d. it was very faint at visible wavelengths but extremely bright at radio wavelengths.

d. it was very faint at visible wavelengths but extremely bright at radio wavelengths.

What are the two physical parameters of stars that are plotted in the Hertzsprung-Russell diagram? a. mass and surface temperature b. luminosity and mass c. radius and mass d. luminosity and surface temperature

d. luminosity and surface temperature

The primary constituents for the organic molecules needed for life do NOT include which one of the following compounds? a. oxygen b. sulfur c. carbon d. silicon

d. silicon

Which of the following events of the past century do you think will have announced our presence on Earth most effectively to extraterrestrial watchers? a. appearance of artificial satellites orbiting Earth after 1957 b. nuclear weapon explosions producing extremely intense but brief flashes of light and electromagnetic radiation c. slow changes in vegetation patterns and the appearance of manmade structures such as road systems and cities on Earth d. slow buildup of radio transmissions after the invention of radio, with modulated signals carrying sound and visual television images

d. slow buildup of radio transmissions after the invention of radio, with modulated signals carrying sound and visual television images

What kind of curvature (geometry of space) does the universe have if the universe is closed? a. parabolic b. flat c. hyperbolic d. spherical

d. spherical

By what standard technique do astronomers find the luminosity class (I, II, III, IV, or V) of a star? a. combining the apparent magnitude with the measured distance to the star b. observing the diameter of the star on a photographic plate or CCD image c. timing how long it takes for the star to be eclipsed by a companion in an eclipsing binary star system d. studying the absorption lines in the star's spectrum

d. studying the absorption lines in the star's spectrum

The radio emission from the jets in a double radio source is d. recombination radiation from electrons combining with protons to form neutral hydrogen gas as the gas cools within the jets. c. 21-cm emission from neutral hydrogen atoms. b. thermal emission from very hot matter ejected from the accretion disk around the central black hole. d. synchrotron radiation from relativistic electrons spiraling in magnetic fields.

d. synchrotron radiation from relativistic electrons spiraling in magnetic fields.

The very last nuclear process to occur at the center of a massive star (at the end of its life) is a. the helium flash. b. silicon fusion, resulting in the production of iron. c. the photodisintegration of nuclei by gamma rays. d. the capture of electrons by protons to produce neutrons.

d. the capture of electrons by protons to produce neutrons.

Scientists are now targeting Europa, one of Jupiter's moons, as a likely site for searching for elementary life-forms because a. radio signals that follow a recognizable pattern have been detected from this moon. b. there appears to be large amounts of dark organic material spread on its surface. c. changes seen in the dark lines crossing the icy surface have a spectral signature of vegetation. d. there is strong evidence for liquid water beneath the thick ice layer on its surface.

d. there is strong evidence for liquid water beneath the thick ice layer on its surface.

Which of the following phenomena was probably NOT a source of large organic molecules, the building blocks of life, on the early Earth? a. comets b. meteorites c. lightning flashes in the early terrestrial atmosphere d. volcanic eruptions

d. volcanic eruptions

An astronomer plots the H-R diagram of a star cluster and finds that it contains hot B-type stars on the main sequence and cooler G- and K-type stars noticeably above the main sequence. This cluster is a. very young because the G and K stars are still evolving toward the main sequence. b. of indeterminate age since the age of the cluster cannot be estimated from the information given. c. impossible because cool stars cannot exist above the main sequence when hot stars are on the main sequence. d. old because the G and K stars are already evolving off (away from) the main sequence.

NOT: c. impossible because cool stars cannot exist above the main sequence when hot stars are on the main sequence.

What mechanism appears to produce the double radio sources seen in intergalactic space? a. two oppositely directed jets of matter, ejected from a small source b. two radio galaxies orbiting each other much like two binary stars c. radio-bright galaxy with a dark absorbing disk edge-on to Earth, splitting the source into two as seen from Earth d. two black holes orbiting around a small but massive galactic nucleus

NOT: c. radio-bright galaxy with a dark absorbing disk edge-on to Earth, splitting the source into two as seen from Earth

A star on the asymptotic giant branch (AGB) is a a. cool main-sequence star. b. blue supergiant. c. star in its first red-giant phase. d. red supergiant.

NOT: c. star in its first red-giant phase.

If the universe is only 14 billion years old, which of the following groups of stars have never moved beyond the main sequence? a. stars with masses less than 0.08 solar mass b. stars with masses less than 0.75 solar mass c. stars with masses greater than 100 solar masses d. stars with masses greater than 10 solar masses

NOT: c. stars with masses greater than 100 solar masses

In general, how many fundamentally different types of black holes are expected to exist? a. only one—all properties but mass are destroyed when a black hole is created b. two—those that have electric charge and those that have no electric charge c. three—atomic-mass black holes, stellar-mass black holes, and supermassive black holes d. two—those that rotate and those that do not rotate

NOT: c. three—atomic-mass black holes, stellar-mass black holes, and supermassive black holes

The ratio of thickness to diameter of the Milky Way Galaxy is a. 1/500. b. 1/5. c. 1/50. d. 1/1000.

NOT: d. 1/1000.

The Drake equation calculates the number of technically advanced civilizations in the galaxy as a product of seven factors: R* fp ne fl fi fc L. In the sample calculation in the text, these values are taken as 1 × 1 × 0.1 × 1 × 1 × 1 × 100 = 10. If we were to redo the calculation, increasing each increasable factor by a multiple of ten, what would the result be? a. 10 b. 104 c. 106 d. 108

NOT: d. 108

Quasars emit significant amounts of radiation from the Lymanα transition. When the spectrum is observed on Earth, it is found that the Lymanα line is accompanied by many absorption lines, called the Lymanα forest. What is the origin of these lines? (See Figure 17-5, Comins and Kaufmann, Discovering the Universe, 8th ed.) a. The absorption lines are caused by the rotation of the quasar. Different parts of the quasar thus give rise to Lyman-alpha lines with different Doppler shifts. b. The absorption lines are the result of gravitational lensing by objects between the quasar and Earth. c. The emitted Lyman-alpha radiation is absorbed by many gas clouds between the quasar and Earth. The lines are receding at various velocities and thus are absorbed at different Doppler-shifted wavelengths. d. Because the quasar's jets are aimed at various directions, the jet plasma has Doppler shifts that are different from those of the quasar itself. The result is a variety of Lyman-alpha wavelengths in the spectrum received on Earth.

NOT: d. Because the quasar's jets are aimed at various directions, the jet plasma has Doppler shifts that are different from those of the quasar itself. The result is a variety of Lyman-alpha wavelengths in the spectrum received on Earth.

What is the current state of the search for extraterrestrial radio communications? a. Several extraterrestrial civilizations have been found, but they are not intelligent enough for us to bother with and the search is continuing. b. Occasional single-frequency searches have been made for extraterrestrial signals, but funds are still being sought for the first major continuous monitoring effort. c. A number of frequencies in the "water hole" are being monitored, but there has been no major effort as yet to send out continuous signals from Earth at these frequencies. d. Continuous transmissions are being sent out from Earth at several frequencies in the "water hole," and tens of millions of other frequencies are being monitored.

NOT: d. Continuous transmissions are being sent out from Earth at several frequencies in the "water hole," and tens of millions of other frequencies are being monitored.

What appears to be the relationship between the distribution of dark matter and the distribution of luminous matter? a. There seems to be no correlation at all. b. There seems to be a separate distribution of dark matter—dark-matter galaxy clusters, voids in the dark matter, and so on. But these formations all occur in regions of space far from luminous matter. c. The distribution of dark matter seems to coincide with the distribution of luminous matter. d. The distribution of dark matter seems to be just the reverse of the distribution of luminous matter: Dark-matter galaxy clusters occur in the voids of luminous matter; luminous galaxy clusters occur in the voids of dark matter.

NOT: d. The distribution of dark matter seems to be just the reverse of the distribution of luminous matter: Dark-matter galaxy clusters occur in the voids of luminous matter; luminous galaxy clusters occur in the voids of dark matter.

How do the youngest, most distant galaxies compare with the older galaxies we see closer to us today? a. The youngest galaxies are bluer and brighter than the older ones. b. The youngest galaxies have the same color as the older ones but are significantly brighter. c. There is no observable difference between the youngest galaxies and the older ones. d. The youngest galaxies are redder and fainter than the older ones.

NOT: d. The youngest galaxies are redder and fainter than the older ones.

How far away is the nearest star beyond the Sun, in parsecs? a. between 1 and 2 pc b. about 12 pc c. about 4 pc d. between 1/2 and 1 pc

NOT: d. between 1/2 and 1 pc

You are observing a binary system with two stars of masses M1 and M2. You determine a, the semimajor axis (also the average distance between the stars) and P, the period of their motion. Using this information in Kepler's Third Law you can calculate a. M1 or M2 but not both. b. M1/M2. c. M1 + M2. d. both M1 and M2.

NOT: d. both M1 and M2.

Several lines of evidence now suggest that large and complex organic molecules can exist or could evolve in outer space, from which the building blocks of life could be formed. Which of the following is NOT one of these observational findings? a. radio astronomical observations of large organic molecules in giant molecular clouds b. discovery of organic molecules inside some meteorites c. discovery by the Viking landers of large organic molecules in the Martian regolith d. laboratory experiments in which electrical sparks passing through a combination of simple gases such as H2O, H2, N2, and CO2 produced large organic molecules

NOT: d. laboratory experiments in which electrical sparks passing through a combination of simple gases such as H2O, H2, N2, and CO2 produced large organic molecules

Which kind of stars are the major source of energy for the heating of the dust clouds and the H II emission nebulae in the planes of the Milky Way and other galaxies? a. hot, young O and B stars, via their UV radiation b. numerous old red giant K and M stars, via their IR heat radiation c. very hot white dwarf stars, the remnants of planetary nebulae in the gas clouds d. many nova and supernova explosions of stars within the gas and dust clouds

NOT: d. many nova and supernova explosions of stars within the gas and dust clouds

What observational fact convinces astronomers that the source of energy in a typical quasar is physically very small? a. rapid variation in the energy output of the source b. extreme distance of all quasars c. starlike appearance of quasars in the Earth's sky d. narrowness of the emission lines in the spectra of quasars

NOT: d. narrowness of the emission lines in the spectra of quasars

Which stars undergo a helium flash in their cores? a. stars of less than 2 solar masses b. stars that contain helium c. stars of more than 2 solar masses d. stars that have become red giants

NOT: d. stars that have become red giants

One of the big puzzles about the properties and behavior of large clusters of galaxies is that a. each cluster appears to consist of the same type of galaxy, some made up totally of spiral galaxies while others contain only ellipticals. b. they appear to be spread uniformly throughout space in all directions, which is difficult to explain with the Big Bang theory. c. there appears to be insufficient mass in the luminous matter (stars, and so on) to hold the cluster together gravitationally. d. they appear not to take part in the general expansion of the universe, in contrast to single separate galaxies, probably because they are gravitationally bound to one another.

NOT: d. they appear not to take part in the general expansion of the universe, in contrast to single separate galaxies, probably because they are gravitationally bound to one another.

The Milky Way Galaxy appears to have a spiral structure with a. four separate major arms. b. three loosely wound arms. c. one "arm" wound around the nucleus four times. d. two major arms wound twice around the nucleus.

NOT: d. two major arms wound twice around the nucleus.

The fact that matter exists today is evidence that matter particles outnumber antimatter particles in the universe. This imbalance was caused by matter inflation. symmetry breaking. chirality. the cosmic overshift.

NOT: matter inflation.

Suppose the Sun became a 1-solar-mass Schwarzschild black hole. What would be its Schwarzschild radius? (See Toolbox 14-1.) a. 2 × 10-8 AU b. 7 × 10-3 AU c. 5 AU d. 3000 AU

a. 2 × 10-8 AU

The cosmological redshift in the light from distant galaxies is explained by which of the following effects? a. A photon's wavelength is a distance and is therefore lengthened by the general expansion of the universe, making the light appear reddened. b. The light we on Earth see was Doppler-shifted to longer wavelengths by the motion of the objects (e.g., galaxies) away from Earth. c. The light spreads out over larger areas as distance increases according to 1/(distance)2, which causes the wavelength to increase in proportion to distance. d. The light from more distant galaxies has traveled through the gravitational fields of more galaxies in getting to us and is therefore more gravitationally redshifted.

a. A photon's wavelength is a distance and is therefore lengthened by the general expansion of the universe, making the light appear reddened.

What condition is necessary for the universe to be closed? a. The universe must have no mass in it. b. The density of the universe must be large. c. The density of the universe must be small. d. The cosmological constant must be large.

b. The density of the universe must be large.

What is the difference between a proton and a neutron in terms of their constituent quarks? a. A proton is made of two "up" quarks and a "down" quark, and a neutron is made of two "down" quarks and an "up" quark. b. A proton is made of two "down" quarks and an "up" quark, and a neutron is made of two "up" quarks and a "down" quark. c. A proton is made of three "up" quarks, and a neutron is made of three "down" quarks. d. A proton is made of three "down" quarks, and a neutron is made of three "up" quarks.

a. A proton is made of two "up" quarks and a "down" quark, and a neutron is made of two "down" quarks and an "up" quark.

For which one of the following objects has the phenomenon of differential rotation NOT been observed? a. Mars b. Jupiter c. Sun d. Milky Way Galaxy

a. Mars

What is the best way to estimate the age of a star cluster? a. Plot the stars on a Hertzsprung-Russell diagram and see which stars are still on the main sequence. b. Measure the motions of the stars in the cluster and compare the measurements with theoretical models. c. Measure the heavy element abundance for the stars in the cluster. d. Count the number of T Tauri stars in the cluster.

a. Plot the stars on a Hertzsprung-Russell diagram and see which stars are still on the main sequence.

For which of the following factors in the Drake Equation do we actually have observational knowledge rather than just a speculative estimate? a. R*, the rate at which solar-type stars form in the Galaxy b. fl, the fraction of Earthlike planets on which life actually arises c. fi, the fraction of life-forms that evolve into intelligent species d. fc, the fraction of intelligent species that develop adequate technology and then choose to send messages out into space

a. R*, the rate at which solar-type stars form in the Galaxy

Supposedly nothing can escape from a black hole, yet astronomers are locating black hole candidates by the X rays they emit. How can X rays be coming from a black hole? a. The X rays come from a highly compressed region in an accretion disk outside the event horizon of the black hole. b. X rays are not light or matter and can therefore escape from inside the black hole. c. If the black hole is rotating, it modifies spacetime around it so much that particles and X rays are created in the vacuum just outside the event horizon. d. The X rays are produced by vibrations of the black hole itself and therefore do not come from inside the black hole.

a. The X rays come from a highly compressed region in an accretion disk outside the event horizon of the black hole.

When the universe was about 2500 years old, the radiation density had decreased to the point where it was equal to the matter density. Yet it was only many years later that atoms formed. What happened to make possible the formation of atoms? a. The average photon energy decreased until it could no longer ionize hydrogen. b. Radiation pressure decreased until it was equal to the inward pressure due to gravity. c. The temperature reached the point where the reaction 4 1H → 4He could proceed. d. Neutrons decayed to produce protons and electrons, the building blocks of atoms.

a. The average photon energy decreased until it could no longer ionize hydrogen.

The explosion of a supernova appears to leave behind a. a rapidly expanding shell of gas and a central neutron star. b. a rapidly rotating shell of gas, dust, and radiation, but no central object. c. a rapidly expanding shell of gas and a compact white dwarf star at its center. d. nothing; the explosion changes all the matter completely into energy, which then radiates into space at the speed of light.

a. a rapidly expanding shell of gas and a central neutron star.

The classical laboratory experiments performed by Urey and Miller to explore the necessary conditions for the production of organic molecules (the building blocks of living things) in the solar system involved the passing of electrical discharges through what mixure of gases? a. ammonia, methane, water vapor, and hydrogen b. carbon dioxide, water vapor, and dust c. hydrogen and helium d. nitrogen, oxygen, water vapor, and carbon dioxide

a. ammonia, methane, water vapor, and hydrogen

In a binary star system, an unseen component is found to have 8 solar masses. It would be visible if the system were a normal star, so it must be a collapsed object. Theoretical considerations tell us that it must be a a. black hole. b. neutron star. c. white dwarf. d. brown dwarf.

a. black hole.

If the density of matter in the universe turned out to be greater than the critical density, it would imply that the universe is a. closed. b. open. c. oscillating. d. contracting.

a. closed.

Particle degeneracies stemming from the Pauli exclusion principle support stars of various masses. Which of the following lists arranges these degeneracies in increasing order of the amount of mass they can support? a. electron, neutron, quark b. electron, quark, neutron c. quark, neutron, electron d. neutron, electron, quark

a. electron, neutron, quark

How many fundamental forces are known in science at the present time under normal conditions? a. four b. five c. three d. six

a. four

Where would you look for a supermassive black hole? a. in the center of a galaxy b. at the center of the universe c. orbiting a normal star in the Milky Way Galaxy d. at the center of a supernova remnant

a. in the center of a galaxy

Black holes do not possess a magnetic field because a. magnetic field is radiated away in the form of gravitational waves during the collapse. b. black holes cannot have electric charge, which is needed to create a magnetic field. c. magnetic fields are created by spinning charges, and black holes cannot spin. d. an object with a magnetic field cannot collapse into a black hole.

a. magnetic field is radiated away in the form of gravitational waves during the collapse.

Which of the following important atomic or molecular species is difficult to detect in the interstellar medium? a. molecular hydrogen (H2) b. atomic hydrogen (H) c. carbon monoxide (CO) d. water vapor (H2O)

a. molecular hydrogen (H2)

The X-ray source Cygnus X-1 is a black hole candidate located in a binary star system. The X-ray source is believed to occupy a volume smaller than Earth. This size is deduced from a. rapid flickering in the X-ray brightness of Cygnus X-1. b. Cygnus X-1's apparent magnitude and distance. c. Cygnus X-1's luminosity and spectral class. d. the shortness of Cygnus X-1's orbital period.

a. rapid flickering in the X-ray brightness of Cygnus X-1.

What is believed to be the solar mass of the black hole candidate at the center of the galaxy M87? a. 3 million b. 3 billion c. 300,000 d. 300

b. 3 billion

The light that arrives at Earth from the Coma cluster of galaxies has traveled for approximately how long? a. 300 billion years b. 300 million years c. 92 million years d. 30 million years

b. 300 million years

The first successful detection of signals from extraterrestrial civilizations was accomplished in which year? a. 1985 b. Never—no such signals have been detected yet. c. 1999 d. 1960

b. Never—no such signals have been detected yet.

Which of the following amazing observational facts about quasars and their behavior is perhaps the most extraordinary? a. Quasars have incredible power as radio emitters, such that simple receivers can detect them from vast distances across the universe. b. Quasars have an energy output equivalent to more than 100 ordinary galaxies from a volume as small as our planetary system. c. The distance of quasars from the Sun is up to 18 billion ly. d. The recession velocities or quasars can be up to 9/10 of the speed of light.

b. Quasars have an energy output equivalent to more than 100 ordinary galaxies from a volume as small as our planetary system.

A space freighter accidentally drops a steel beam while passing a black hole, and the beam starts falling toward the black hole with the long direction of the beam pointing toward the black hole. What happens to the beam as it approaches the event horizon? a. The beam expands in all dimensions to the size of the black hole event horizon when it reaches this distance from the singularity. b. The beam is stretched in length and compressed in width. c. The beam is compressed in both length and width. d. The beam is compressed in length and stretched in width.

b. The beam is stretched in length and compressed in width.

There is a mass limit for a star in the white-dwarf phase, the Chandrasakhar limit, beyond which the electron degeneracy pressure can no longer support the star against its own gravity. This limit is a. 0.2 solar mass. b. 30 solar masses. c. 1.4 solar masses. d. 14 solar masses.

c. 1.4 solar masses.

Fe XII is an ionized iron atom with a. 13 electrons removed. b. 1 electron removed. c. 11 electrons removed. d. 12 electrons removed.

c. 11 electrons removed.

If we do eventually make contact with other civilizations across space, which of the following conditions will inevitably hold? a. We will not be able to understand the messages. b. The civilization is likely to be very much more technologically primitive than ours. c. Conversations will take a very long time. d. The chemistry and biology of the life-forms are likely to be very different from ours—for example, silicon-based rather than carbon-based.

c. Conversations will take a very long time.

In the asymptotic giant branch (AGB) phase of their lives, stars like the Sun lose mass to space through an outflowing "stellar wind." Over a period of 1000 years, how much mass would such a star eject? a. almost 1/10 solar mass b. about 10-5 solar mass c. about 1/100 solar mass d. almost none since most of the mass flows back in at the star's poles

c. about 1/100 solar mass

What fraction of the mass of the Milky Way Galaxy is in a form that we have been able to see? a. about 50% b. 100%—who ever heard of matter that can't be seen? c. about 10% d. about 90%

c. about 10%

Suppose that an astronomical observatory announces the discovery of an object with about 50 times the mass of Jupiter. Since this mass is not enough for the object to be a star, what name would the observatory apply to the object? a. red dwarf b. infrared dwarf c. brown dwarf d. white dwarf

c. brown dwarf

The largest range of sizes of galaxies is found in which class of galaxies? a. spiral galaxies b. irregular galaxies c. elliptical galaxies d. starburst galaxies

c. elliptical galaxies

The source of a protostar's heat is aa. gravitational energy released as the protostar expands. b. nuclear reactions converting helium to carbon and oxygen in its core. c. gravitational energy released as the star contracts. d. nuclear reactions converting hydrogen into helium in its core.

c. gravitational energy released as the star contracts.

The one component of the material of the Milky Way Galaxy that prevents us from seeing and photographing the galactic center at optical wavelengths is d. very cold hydrogen gas. c. interstellar dust. c. the glare of light from nearby stars. d. hot hydrogen gas.

c. interstellar dust.

Pulsating X-ray sources with periods of a few seconds are caused by a. the eclipsing of an X-ray-emitting star with a very hot surface by a cool companion in a close binary system. b. the pulsation in radius, temperature, and hence luminosity of a hot Cepheid variable star with a surface temperature hot enough to emit X rays. c. matter falling violently onto the surface of a rotating neutron star from a close companion in a binary star system, causing an X-ray hot spot that disappears periodically behind the neutron star. d. matter falling onto the surface of a very hot, rotating white dwarf star from an ordinary companion star in a binary system, producing an X-ray-emitting hot spot that disappears periodically behind the white dwarf.

c. matter falling violently onto the surface of a rotating neutron star from a close companion in a binary star system, causing an X-ray hot spot that disappears periodically behind the neutron star.

Suppose you were far from a planet that had a very strong gravitational field and you were watching a clock on the surface of the planet. During the time in which your own clock ticks out a time of 1 hour, how much time does the clock on the planet tick out? a. less than 1 hour (but more than zero) b. no time at all c. more than 1 hour d. exactly 1 hour, the same as yours

c. more than 1 hour

In which of the following "frames of reference" would matter behave exactly as it would in a stationary frame of reference? a. accelerating downward in an elevator whose cable has broken b. moving upward against gravity in an elevator as it accelerates from rest c. moving at a constant velocity d. moving at a constant speed in a circular path, such as in an orbit

c. moving at a constant velocity

A black hole is so named because a. the gravitational field is so high that the wavelength of its emitted light is gravitationally redshifted to radio wavelengths. b. it emits no visible light because it is so cold, less than 100 K. c. no light can escape from it due to its powerful gravitational field. d. it is colder that the rest of the universe; that is, its effective temperature is less than 3 K.

c. no light can escape from it due to its powerful gravitational field.

If the central engine of a double-lobed radio source is a black hole swallowing matter from an accretion disk, where do the jets of matter come from that we see traveling outward from the galaxy? a. The jets are accelerated in the ergoregion of the rotating black hole and ejected outward in the black hole's equatorial plane. b. The jets are composed of material that has been accelerated from two hemispheres toward the black hole with such speed that it escapes again on two opposite sides of the black hole. c. The jets arise in the weak galactic magnetic field, not in the region near the black hole. d. The jets are squirted out by high pressure in the accretion disk before the matter reaches the black hole.

d. The jets are squirted out by high pressure in the accretion disk before the matter reaches the black hole.

In terms of the mass and lifetime of a star, which of the following statements is true? a. The mass of a star has no bearing on the length of a star's life or the speed of its evolution. b. Stars of about 1 solar mass have the shortest lives; less massive stars evolve slowly and live a longer time, while more massive stars have long lives because of the large amount of fuel they contain. c. The less massive the star, the shorter is its life because it has less hydrogen "fuel" to burn. d. The more massive the star, the faster it evolves through its life.

d. The more massive the star, the faster it evolves through its life.

Most of the light from a galaxy comes from the inner parts. If this means that most of the galaxy's mass is also in the inner region, then how would we expect the galaxy's speed of rotation to behave in its outer region? a. The rotation speed should increase with increasing distance from the center. b. The rotation speed should decrease sharply to zero at the outer edge of the visible galaxy. c. The rotation speed should not change appreciably with increasing distance from the center (i.e., a "flat" rotation curve). d. The rotation speed should decrease smoothly with increasing distance from the center.

d. The rotation speed should decrease smoothly with increasing distance from the center.

What is believed to prevent stars from being larger than a few hundred solar masses? a. Stars of larger mass would collapse under their own gravity and become black holes. b. No interstellar clouds have masses of more than 100 solar masses. c. The cores of larger-mass stars would run through their lives and explode before the stars finish contracting as protostars. d. The temperature becomes so high that the excess mass is pushed back into space by radiation from the star.

d. The temperature becomes so high that the excess mass is pushed back into space by radiation from the star.

Which of the following statements correctly describes the universe for the entire first 500,000 years of its life? a. The universe was filled with free quarks (not confined inside neutrons or protons). b. All the fundamental forces of nature were unified into one force. c. The universe was a filled with a sea of nuclear particles undergoing violent reactions. d. The universe was opaque.

d. The universe was opaque.

Which of the following molecules produces the strong absorption bands in the spectrum of a cool M-type star, as can be seen in Figure 11-5 of Comins and Kaufmann, Discovering the Universe, 8th ed.? a. HCl, hydrogen chloride b. CaI, calcium iodide c. H2O, water vapor d. TiO, titanium oxide

d. TiO, titanium oxide

A star with a surface temperature of 4000 K and a luminosity of about 10-2 times that of the Sun is a member of which luminosity class? (See Figure 11-10, Comins and Kaufmann, Discovering the Universe, 8th ed.) a. III, giant b. I, supergiant c. II, bright giant d. V, main-sequence

d. V, main-sequence

What fraction of the mass of the Milky Way Galaxy appears to be in the form of "dark matter," which we cannot see but can detect through its gravitational influence? a. about 50% b. a bout 10% c. 0%—who ever heard of matter that can't be seen? d. about 90%

d. about 90%

Which of the following objects is NOT classified as an active galaxy? a. Seyfert galaxy b. BL Lacertae object c. quasar d. barred spiral

d. barred spiral

The source of the hot, intergalactic gas in many rich, regular clusters of galaxies appears to be a. jets of gas ejected by supermassive black holes at the centers of the galaxies. b. bursts of star formation in merging galaxies. c. exploding stars or supernovae within individual galaxies. d. collisions between galaxies in the cluster.

d. collisions between galaxies in the cluster.

Which one of the following occurrences has NOT been observed as evidence of colliding galaxies? a. very strong X-ray emission coming from rich clusters of galaxies b. starburst galaxies that contain hot gas, many newborn stars, and relatively young globular clusters c. streams of hydrogen gas connecting two or more galaxies d. distribution of black hole candidates throughout a galaxy suggesting many star mergers as a result of a galactic collision

d. distribution of black hole candidates throughout a galaxy suggesting many star mergers as a result of a galactic collision

Which of the four fundamental forces holds the electrons in the atom? a. strong nuclear force b. gravitational force c. weak nuclear force d. electromagnetic force

d. electromagnetic force

The symbol He II stands for a a. helium atom that has lost two electrons. b. neutral helium atom (atomic number = 2) that has lost no electrons. c. helium molecule that contains two helium atoms. d. helium atom that has lost one electron.

d. helium atom that has lost one electron.

If we are going to "listen" for electromagnetic radiation at 21 cm from extraterrestrial sources, then we had better not generate too many waves at this wavelength from terrestrial sources. The standard FM broadcast band (as you can see by looking at your radio dial) spans frequencies from 88 MHz (million cycles per second) to 108 MHz. How does the frequency of the 21-cm signal compare with the FM band? The frequency of the 21-cm line is a. below the low frequency end of the FM band by a factor of about 9. b. right in the middle of the FM band. c. right at the upper end of the FM band. d. higher than the top end of the FM band by a factor of about 13.

d. higher than the top end of the FM band by a factor of about 13

At which of the following locations will Newton's laws of motion be inadequate in describing precisely the motions of objects? a. in the Space Shuttle, moving around Earth at a speed of about 8 km/sec b. at the center of Earth c. inside an artillery shell as it accelerates inside the gun barrel d. inside the orbit of Mercury

d. inside the orbit of Mercury