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the physical universe

Questions and Answers of The Physical Universe

Clouds of luminous gas and dust in our galaxy are calleda. Galactic clustersb. Galactic nebulas c. Quasarsd. Cosmic rays
Where is most of the interstellar gas in our galaxy located? What is its chief constituent?
Evidence of various kinds suggests that at the center of our galaxy is aa. Quasarb. Pulsar c. Neutron stard. Black hole
Each cubic centimeter of space between the stars in our galaxy contains on the average abouta. 1 atom or moleculeb. 1 million atoms or moleculesc. 1 mg of matterd. 1 g of matter
Distinguish between Population I and Population II stars.
Our galaxy is shaped roughly like a fried egg whose diameter is abouta. twice its thicknessb. 10 times its thicknessc. 100 times its thicknessd. 1 million times its thickness
The stars in the disk of our galaxy are mostly distributeda. Uniformlyb. At randomc. In its central nucleusd. In its spiral arms
What are the properties of globular clusters?
The number of stars in our galaxy is roughlya. 2000b. 2 million c. 2 billiond. 200 billion
Our galaxy is approximatelya. 4 light-years acrossb. 15,000 light-years acrossc. 130,000 light-years acrossd. 4 million light-years across
What is the Milky Way?
Relative to the center of our galaxy,a. Its stars are stationaryb. Its stars move entirely at randomc. Its stars revolved. Population I stars are stationary, and Population II stars revolve
The Milky Way isa. A gas cloud in the solar systemb. A gas cloud in the galaxy of which the sun is a memberc. The galaxy of which the sun is a memberd. A nearby galaxy
The stars in space area. Uniformly spread outb. Distributed completely at randomc. Chiefly in the Milky Wayd. Mostly contained within widely separated galaxies
What prevents light from escaping from a black hole?
(a) What is the characteristic behavior of a pulsar? (b) What is believed to be its nature? (c) From what does a pulsar originate?
What is left behind after a supernova explosion?
After a very long time, a white dwarf will cool down and become a black dwarf. What will the corresponding evolutionary path of the star be on the H-R diagram?
In what part of its life cycle is a white dwarf?
Why are there relatively few giant stars in the main sequence?
Sirius, the brightest star in the sky apart from the sun, is a blue-white star of great luminosity. (a) What does this suggest about its temperature? (b) About its average density? (c)
What are the chief characteristics of an average star in the upper left of the H-R diagram? In the lower left? In the upper right? In the middle of the main sequence?
Why must a star have a certain minimum mass in order to radiate?
Black holes are remnants ofa. Stars with small massesb. Stars with large massesc. White dwarfsd. Black dwarfs
Why are most stars part of the main sequence on the H-R diagram?
A black hole appears black becausea. It is too cool to radiateb. It is surrounded by an absorbing layer of gasc. Its gravitational field is too strong to permit light to escaped. Its magnetic field
A pulsar is nota. The remnant of a supernova explosionb. Rotating rapidlyc. Composed largely of neutronsd. As large as the earth
Is it possible for an object with the mass and composition of the sun to exist without radiating energy?
The heaviest elements are created ina. Stellar interiorsb. Stellar atmospheresc. Black holesd. Supernova explosions
The brightest of the following types of stars is aa. Giantb. White dwarf c. Supernovad. Neutron star
Must a star be spherical?
A supernova explosion may leave behind which one or more of the following?a. A black holeb. A neutron star c. A pulsard. A giant
A star that explodes as a supernovaa. Has a mass much greater than that of the sunb. Has a mass much smaller than that of the sunc. Has a mass about equal to that of the sund. May have any mass
How is a star’s diameter estimated from measurements of temperature and luminosity?
A brown dwarfa. Has less mass than Jupiterb. Is a member of the main sequencec. Is on its way to becoming a black dwarfd. Was never a true star
A star like the sun eventually becomes aa. Black holeb. White dwarf c. Supernovad. Neutron star
Which stars do you think have the highest densities? The lowest?
When the hydrogen supply in a typical main-sequence star begins to run out, other nuclear reactions occur and the star becomes aa. Giantb. White dwarf c. Supernovad. Neutron star
A typical white dwarf star is about the size of a. A large buildingb. The moon c. The earthd. Jupiter
Which varies more, the masses of the stars or their sizes?
White dwarfs are stars that area. At the beginning of their life cyclesb. In the middle of their life cyclesc. At the end of their life cyclesd. Any of these choices is correct.
The main sequence on the H-R diagram includesa. The sun b. White dwarfs c. Giantsd. Pulsars
Explain how the distance to a star cluster that contains Cepheid variables is determined.
The greater the mass of a main-sequence star, thea. Younger it isb. Longer it will remain part of the main sequencec. Less hydrogen it containsd. Hotter it is
Stars at the upper end of the main sequence havea. High temperatures and large massesb. High temperatures and small massesc. Low temperatures and large massesd. Low temperatures and small masses
According to the text, the sun’s mass is about 2 × 1030 kg and it loses about 4 × 109 kg per second as its hydrogen is converted into helium. Assuming that the sun has been radiating energy at
Stars belonging to the main sequencea. Have the same massb. Have the same temperaturec. Radiate at steady ratesd. Fluctuate markedly in brightness
The reason stars more than about 100 times as massive as the sun are not found is thata. They would split into double-star systemsb. They would be black holes from which no light can escapec. The
The color of a relatively cool star isa. Whiteb. Yellow c. Blued. Red
What aspect of the formation of helium from hydrogen results in the evolution of energy?
Variations among stars are least in theira. distance from the sunb. massc. sized. temperature
The temperature of a star can be determined froma. The wavelength at which its radiation is brightestb. The wavelength at which its radiation is dimmestc. Its apparent brightnessd. The strength of
Intense auroral activity occurs in the earth’s upper atmosphere about 30 h after a solar storm. What is the average speed of the ions emitted during the storm?
The temperature of a star can be determined froma. the wavelength at which its radiation is brightestb. the wavelength at which its radiation is dimmestc. its apparent brightnessd. the strength of
If we know the surface temperature and luminosity of a star, we can find itsa. Massb. Size c. Aged. Distance
If we know the surface temperature and luminosity of a star, we can find itsa. massb. size c. aged. distance
What aspect of sunspots changes during a sunspot cycle?
Binary stars are valuable to astronomers because they permit the determination of stellara. diametersb. distances c. massesd. temperatures
Stars whose luminosity and period of variation are related are calleda. Pulsarsb. Cepheid variables c. Main-sequence starsd. Giants
Stars whose luminosity and period of variation are related are calleda. pulsarsb. Cepheid variables c. main-sequence starsd. giants
If we know both the luminosity and brightness of a star, we can find itsa. Massb. Temperature c. Distanced. Age
Suppose the earth’s magnetic field were to disappear. What effect would this have on the aurora?
If we know both the luminosity and brightness of a star, we can find itsa. massb. temperature c. distanced. age
Proxima Centauri, the closest star to the sun, is at a distance of abouta. 4 light-yearsb. 400 light-years c. 4 million light-yearsd. 4 billion light-years
Proxima Centauri, the closest star to the sun, is at a distance of abouta. 4 light-yearsb. 400 light-years c. 4 million light-yearsd. 4 billion light-years
The sun’s energy comes froma. Nuclear fissionb. Radioactivityc. The conversion of hydrogen to heliumd. The conversion of helium to hydrogen
What happens to the radiation emitted underneath the photosphere of the sun?
The sun’s energy comes froma. nuclear fissionb. radioactivityc. the conversion of hydrogen to heliumd. the conversion of helium to hydrogen
The sun does nota. have a magnetic fieldb. have a solid corec. revolve about an axisd. consist largely of ions
The temperature of the sun’s interior is believed to be abouta. 600 Kb. 6000 K c. 15 million Kd. 15 billion K
Why is the sun’s corona ordinarily not visible? How do we know it exists?
The temperature of the sun’s interior is believed to be abouta. 600 Kb. 6000 Kc. 15 million Kd. 15 billion K
Solar storms may affect which one(s) of these?a. The earth’s magnetic fieldb. Electric transmission linesc. Shortwave radio receptiond. Satellite electronics
Solar storms may affect which one(s) of these?a. the earth’s magnetic fieldb. electric transmission linesc. shortwave radio receptiond. satellite electronics
The number of sunspotsa. Remains approximately constantb. Increases and decreases at random intervalsc. Increases and decreases in a yearly cycled. Increases and decreases in an 11-year cycle
How can the composition of the sun be determined?
The number of sunspotsa. remains approximately constantb. increases and decreases at random intervalsc. increases and decreases in a yearly cycled. increases and decreases in an 11-year cycle
Sunspots area. Dark clouds in the sun’s atmosphereb. Regions somewhat cooler than the rest of the sun’s surfacec. Regions somewhat hotter than the rest of the sun’s surfaced. Of unknown nature
Sunspots area. dark clouds in the sun’s atmosphereb. regions somewhat cooler than the rest of the sun’s surfacec. regions somewhat hotter than the rest of the sun’s surfaced. of unknown nature
The solar winda. Blows over the sun’s surfaceb. Consists of photons streaming from the sunc. Consists of ions streaming from the sund. Consists of hydrogen atoms streaming from the sun
Suppose you examine the spectra of two stars receding from the earth and find that the lines in one are displaced farther toward the red end than those in the other. What conclusion can you draw?
The solar winda. blows over the sun’s surfaceb. consists of photons streaming from the sunc. consists of ions streaming from the sund. consists of hydrogen atoms streaming from the sun
Auroras occur mainly in the polar regions because of the effect ofa. The moonb. Low temperatures therec. The geomagnetic fieldd. The earth’s equatorial bulge
Auroras occur mainly in the polar regions because of the effect ofa. the moonb. low temperatures therec. the geomagnetic fieldd. the earth’s equatorial bulge
Auroras are caused bya. Streams of colored gases from the sunb. Streams of charged particles from the sunc. Cometsd. Micrometeorites
Suppose a star had a cool interior surrounded by a hot atmosphere. What kind of spectrum would it have?
Auroras are caused bya. streams of colored gases from the sunb. streams of charged particles from the sunc. cometsd. micrometeorites
The sun’s atmospherea. Extends out into the solar systemb. Consists mainly of oxygen and nitrogenc. Consists of burning hydrogend. Is relatively cool
The sun’s atmospherea. extends out into the solar systemb. consists mainly of oxygen and nitrogenc. consists of burning hydrogend. is relatively cool
The surface temperature of the sun is approximatelya. 600 Kb. 6000 K c. 6 million Kd. 16 million K
Why do you think it is useful to put an astronomical telescope in a satellite?
The surface temperature of the sun is approximatelya. 600 K c. 6 million Kb. 6000 K d. 16 million K
The light the sun emits comes froma. Its interiorb. A thin gas layer at its surfacec. A thin liquid layer at its surfaced. A thin solid layer at its surface
The light the sun emits comes froma. its interiorb. a thin gas layer at its surfacec. a thin liquid layer at its surfaced. a thin solid layer at its surface
The examination of starlight with a spectrometer cannot provide information about an isolated star’sa. Temperatureb. Structure c. Massd. Magnetic field
Why do stars seem to twinkle?
The examination of starlight with a spectrometer cannot provide information about an isolated star’sa. temperaturec. massb. structure d. magnetic field
Most stars have hot interiors surrounded by relatively cool atmospheres. The spectrum of such a star consists ofa. White lines against a dark backgroundb. Colored lines against a dark backgroundc.
Most stars have hot interiors surrounded by relatively cool atmospheres. The spectrum of such a star consists ofa. white lines against a dark backgroundb. colored lines against a dark backgroundc.
Compared with a large telescope mirror, a large telescope lensa. Is easier to support against sagb. Does not disperse lightc. Can provide higher magnificationd. Has no advantages

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