Quasars





relatively rapid fluctuations in the electromagnetic output of quasars is an indication of

A the rapid rotation of the sources

B objects moving in front of them from our point of view

C the relatively small size of the emitting regions

D their relative closeness to the milky way



which of the following statements poses the greatest challenge to any viable theory of quasars

A the red shifts of quasars tend to increase as their apparent diameters decrease

B quasars have actual brightnesses which are considerably larger than those of galaxies

C quasars vary their energy output significantly over relatively short spans of time

D quasars look like ordinary stars in an optical telescope



we suspect that quasars are the active centers of galaxies because

A quasar fuzz produces stellar spectra.

B a few quasars have large red shifts.

C some quasars fluctuate rapidly.

D none of these.



which observation seems to indicate that quasars are quite small

A large Doppler shift

B variable light output

C brightest in the infrared

D starlike image



how do astronomers find the distances to quasars?

A by measuring their heliocentric parallax.

B by applying Hubble's law to their red shifts.

C by applying the period-luminosity relationship.

D by applying the mass-luminosity relationship.



the most widely-accepted explanation for the large red shifts of quasars is that

A they obey Hubble's law.

B they are ejected from galaxies.

C of a gravitational red shift.

D of a new physics needed to understand the phenomenon.



which of the following is not true of quasars

A the name means "quasi-stellar-source"

B they show marked radio radiation

C they are receding from us at great speeds

D they are extremely large in diameter



in a quasar, which wavelength is brightest

A ultraviolet

B visual

C infrared

D radio



which of the following statements is the best direct evidence that quasars are not part of our galaxy

A the red shifts of quasars tend to increase as their apparent diameters decrease

B quasars have actual brightnesses which are considerably larger than those of galaxies

C quasars vary their energy output significantly over relatively short spans of time

D quasars look like ordinary stars in an optical telescope



it has been suggested that quasars may be giant

A spiral galaxies

B elliptical galaxies

C irregular galaxies

D black holes



which of the following is not a property of quasars

A they are star like in appearance

B they have large red shifts

C they pulsate very regularly in brightness

D much of their emission is at non-visible wavelengths



the size of the quasars is thought to be

A larger than a normal galaxy

B much less than a galaxy but much larger than a star

C about the size of a star

D about the size of the Earth



which of the following objects is brightest in the infrared

A normal galaxy

B colliding galaxies

C radio galaxy

D quasar ("orthodox" interpretation)



if a supermassive black hole drives the activity of an active galaxy, then

A jets can arise from the outflow of material along the spin axis.

B infalling matter forms an accretion disk around it.

C it must be very large, more than 100 light years in diameter.

D (a) and (b).

E (b) and (c).



the great distances of quasars implied by the large red shifts together wit their faint apparent magnitude tells us that quasars are

A highly massive

B very large in diameter

C high temperature objects

D highly luminous



Arp's discordant red shifts refer to groups of galaxies in which

A different galaxies have different red shifts

B some galaxies become quasars

C quasars are emitted from galaxies

D galaxies are still forming



which of the following objects is brightest

A normal galaxy

B exploding galaxy

C radio galaxy

D quasar



which of the following is not a direct observation of quasars

A they emit radio waves

B their light is variable

C they contain a super-massive black hole

D they are star-like in appearance



quasars emit

A less energy than Jupiter

B more energy than our entire galaxy

C as much energy as the sun

D as much energy as the Orion nebula



the evidence for the small size of quasars comes from

A the amount of energy released by them.

B their distance from us.

C the rapidity of their luminosity changes.

D comparison with cepheid variables.

E the magnitude of their blue shift.



all quasars are

A receding from the Earth

B distant stars of exceptional actual brightness

C small brilliant satellites of normal galaxies

D remnants of supernova explosions



quasars appear to be starlike points in the sky. the real size of a quasar can be estimated from

A its emission lines

B its red shift

C its actual brightness

D the period of its fluctuations



it has been suggested in class that quasars may be powered by

A spiral galaxies

B collapsing clouds of gas

C supernovae explosions

D suppermassive black holes



we have observed evidence for a gravitational lens in

A the existence of quasars

B brightness variation of quasars

C the formation of galaxies

D multiple images of a single quasar



the most widely accepted explanation of the red shift of quasars is

A they are nearby but moving quickly

B gravitational

C new physics

D they obey Hubble's law



if a quasar is the hyperactive nucleus of distant, young galaxies, then you would expect

A quasars to be found in distant clusters of galaxies.

B radio jets extending from quasars.

C the surrounding part of the galaxy to be faintly visible.

D all of the above.

E none of the above.



which of the following objects is smallest

A an average cluster of stars

B a galaxy

C a cluster of galaxies

D a quasar



the best evidence that quasars are at cosmological distances is

A their large observed red shift

B their association with clusters of galaxies having the same red shift

C their association with clusters of galaxies having a very different red shift

D their great luminosity



quasars are the ______ and ______ objects in the universe.

A most violent, closest

B most distant, rapidly receding

C youngest, slowest

D coolest, reddest



which of the following is star-like in appearance

A black holes

B super novae

C nebulae

D quasars



a difficult question for the ejection theory of quasars to answer is

A why none are approaching us

B why they are so small

C why they have such high velocities

D why they emit radio waves



by using the Doppler effect to analyze the light of quasars we conclude that they are

A very far away

B very bright

C very small

D moving very rapidly



the largest red shifts are observed in

A distant ordinary galaxies

B seyfert galaxies

C radio galaxies

D quasars



we place a limit on the size of quasars by

A occultation

B interferometry

C time variations

D the red shift



all quasars have emission lines in their spectra. their existence implies that the quasar contains

A a cool, transparent gas.

B a hot, transparent gas.

C a hot, opaque gas.

D many stars like the sun.



we cannot judge quasars' distance by using their absolute luminosity as we do in the case of galaxies because

A they have no absolute luminosity.

B there are no nearby quasars with which to compare distant ones.

C their luminosity is too great.

D their recessional speeds are unknown.



when we see a gravitational lens we can conclude that

A the lensing galaxy is superluminous

B the quasar must be very small

C the quasar and galaxy must be at about the same distance

D the quasar cannot be a local object



if quasars are the most distant objects known, it is difficult to explain

A why they are so large

B why they are receding from us so rapidly

C how anything could be "beyond" the edge of the big bang universe

D how anything so small could be so bright



one possible energy source for quasars may be

A exploding stars.

B electron collisions.

C rapid quasar rotation.

D supermassive black holes.



which of the following is not an observed characteristic of quasars

A emit radio waves

B small in size compared to normal galaxies

C most distant objects in the universe

D move away from us at very high speed



which of the following does not apply to quasars

A they are very far away

B they are very luminous

C they are brightest in the radio part of the spectrum

D their brightness is not constant?



the most remarkable observed feature of quasars is their large

A red shifts in absorption lines.

B red shifts in emission lines.

C blue shifts in emission lines.

D image, as seen through a large telescope.



quasars are believed to be comparatively small because

A objects as large as galaxies do not generate as much energy as quasars

B they appear as small, bluish stars when photographed

C they can change in intensity in a short period of time

D the resemble stars more than galaxies



quasar absorption lines

A have the same red shift as the emission lines

B have greater red shifts than the emission lines

C have smaller red shifts than the emission lines

D are formed in interstellar space



if quasars are relatively nearby, they may be

A formed during supernovae explosions in our own galaxy

B ejected from galaxies

C forming into normal galaxies

D burned out galaxies



what observational evidence do we have that quasars are relatively small in size, the largest being perhaps a few light years across?

A the light output of quasars varies on time scales of days to a few weeks.

B the lines of the quasars' spectra are greatly red-shifted.

C quasars are barely resolved by optical telescopes.

D the radiation output is too intense to be coming from a large object.



quasars are brightest in what part of the spectrum

A x-ray

B radio

C infrared

D visible



which of the following is true about quasars?

A they seem to be extremely large compared to most galaxies.

B they seem to be very small for the energy released.

C if they are as far away as they seem, they are very energetic.

D both (a) and (c) above.

E both (b) and (c) above.



the red shift of quasars can be explained as

A a velocity Doppler shift

B a gravitational red shift

C an affect of the time dependence of the physical constants

D any, all, or none of these



when viewed through a telescope, a quasar appears to be a

A giant irregular galaxy

B spiral galaxy

C cloud of gas

D star



by comparing and contrasting quasars, active galaxies, and the milky way, we might conclude that

A all are essentially the same thing, except that quasars are larger than active galaxies, which in turn are larger than the milky way

B these objects represent an evolutionary sequence, showing that galaxies evolve to become less violent as the universe ages

C galaxies and similar objects were smaller in the distant past than they are today

D objects which are farther away tend to be brighter



quasars appear to be related to

A globular clusters

B galactic clusters

C nuclei of galaxies

D stars



which of the following ideas is the most difficult to understand or explain if quasars are assumed to be very distant?

A the processes which result in a large amount of energy being generated in a small region of space.

B the large red shift in the emission lines.

C the lifetimes of the quasars.

D the chemical composition of the quasars.



quasars were first discovered because of

A the variation in their brightness

B their unusual color

C their radio emission

D their extraordinary brightness



the significance of Arp's groups of galaxies is that

A it is unusual to find galaxies together

B they don't all have the same red shift

C they have the same red shift but are at different distances

D four out of five galaxies are quasars



quasars are known to be very small, compared to galaxies because of

A their small apparent size

B their radio brightness

C their infrared brightness

D the optical variability



the distances to quasars may be determined by

A measuring the size of the quasar.

B measuring the red shift of emission lines.

C measuring the width of the emission lines.

D looking for cepheid variables in the quasar light output.



if quasars are "young" and very far away they could be

A a first phase in the life of galaxies.

B the original big bang.

C a first phase in the life of a single star.

D all of the above.

E none of the above.



which of the following characteristics do at least some AGN's and quasars have in common?

A nuclear radio jet and outer lobes.

B high luminosity (compared to the milky way).

C small region in nucleus producing energy.

D all of the above.

E none of the above.



according to the giant irregular galaxy theory of quasars, they must

A be very large in size

B have very long lifetimes

C have formed immediately following the big bang

D be very far away



the specific characteristics which identify a quasar are

A spiral galaxy appearance, and very high spectral blue shift

B star-like appearance, and very high spectral red shift

C spiral galaxy appearance, but no spectral shift

D star-like appearance, and very high spectral blue shift



the radio emission from quasars is characteristic of

A thermal emission from a hot body

B thermal emission from a cool body

C nonthermal synchrotron emission

D thermal synchrotron emission



the most conspicuous observed property of quasars is their

A high apparent brightness

B high red shift

C high blue shift

D dramatic appearance on photographs



when photographed, quasars appear to be

A black holes surrounded by matter

B stars

C normal giant galaxies

D irregular galaxies



if the red shifts of quasars arise from the expansion of the universe, then

A quasars must be very small.

B quasars must be very luminous.

C quasars must be local.

D all of these.



judging from their Doppler shift, all quasars

A are moving fast relative to us (compared to speeds of most galaxies).

B are moving away from us.

C are very distant.

D all of the above.

E none of the above.



at least some quasars must be small. the evidence for this is

A their small measured angular diameters

B their high luminosity

C their low measured mass

D their rapid fluctuations in luminosity



the active region of a quasar whose light output varies considerably in a month is

A a light-month in size

B a light-year in size

C the size of the milky way

D unknown in size



quasars

A have very large red shifts

B appear star-like in the sky

C are very small compared to galaxies

D all of the above



which of the following locations in our universe has been suggested as the site of a super-massive black hole?

A the center of our quasar

B the center of the universe, as defined by the universal expansion of the observable universe

C the center of the ring nebula in Lyra, an old star

D the center of the crab nebula, an old supernova remnant



why do astronomers believe that quasars' radiation-producing regions must be relatively small?

A the intensity of their synchrotron emission implies that high-speed electrons are confined in a small volume

B their red shifts imply a strong-gravity (and thus much compressed) source

C they change their brightnesses significantly within a few days, and thus t must be only a few "light days" across at most

D they are ejected at high speeds from "peculiar galaxies" and this is possible only for objects of relatively low mass



quasars must be small, because they

A have high radial velocities

B are very luminous

C are surrounded by quasar fuzz

D fluctuate rapidly in brightness



quasars were discovered because of

A their brightness relative to galaxies

B their variability

C their size

D their radio emission



the light variability of quasars implies they are small because

A only small objects such as stars are observed to vary

B light changes from the far side take longer to reach us if they are larger

C large objects could not rotate rapidly enough

D great compression is needed to produce so much energy as quickly



quasars are known to occur within galaxies because

A they are always found in clusters of galaxies

B their spectra are like those of galaxies

C they look like ordinary galaxies

D a faint fuzz of galaxy light can be detected around them



in a normal photograph, a quasar looks like

A a faint planet

B a star

C a dwarf galaxy

D a planetary nebula



early attempts to explain the spectrum of the first quasar were unsuccessful because the lines in the spectrum were

A produced by elements not usually found in stars

B emission rather than absorption

C produced by elements at higher temperatures than usually found in stars

D red-shifted much more than normal



if the red shifts of quasars arise from the expansion of the universe, the

A quasars must be very small

B quasars must be very luminous

C quasars must be close to us

D all of these



quasar absorption lines are best explained as produced

A by intervening galaxies

B by the general intergalactic medium

C in the outer envelope of the quasar

D by the interstellar medium in the milky way



one possible mechanism for energy production in quasars is

A frequent collisions of galaxies in the early universe

B frequent collisions of densely packed black holes

C matter from an accretion disk falling into a supermassive black hole

D supernovae detonations of supermassive stars



a quasar is now thought to be

A a very active, very distant star

B a long-lived supernova explosion

C the central core of an active galaxy

D a nearby star, ejected with great violence out of a galaxy



astronomers believe that the "powerhouses" (energy-emitting regions) in quasars are very small because

A quasars have high red shifts

B quasars are extremely bright in radio waves

C quasars show variations on the time scales of weeks or months

D quasars do not put out much energy, so they don't need very large energy- producing regions



astronomers believe that the source of quasars' enormous energy output is

A millions of concurrent supernova explosions

B mater-antimatter mutual annihilation

C matter falling into very massive "black holes"

D shock waves in very hot, compressed interstellar gas



quasars appear to be star-like points in the sky. the real size of a quasar can be estimated from

A its emission lines

B its red shift

C the period of its light fluctuations

D 21-cm radio emission



which of the following typically has the greatest actual brightness

A quasars

B radio galaxies

C giant elliptical galaxies

D seyfert galaxies



an object which we observe to change in brightness must be small(compared to normal galaxies) because

A large objects cannot change their energy output quickly

B large objects do not pulsate

C the universe is not old enough yet

D light from the distant parts of the object take longer to reach us



all quasars appear to be

A moving in random directions, at high speeds

B relatively close, very bright objects

C moving away from Earth at very high speeds

D very distant, with small actual brightnesses



the traditional explanation of the red shift of quasars is

A they are nearby but moving quickly

B gravitational

C new physics

D they obey Hubble's law



the active regions of quasars are

A larger than normal galaxies

B about the same size as normal galaxies, but much brighter

C about the same size as the solar system, but have greater luminosities than the brightest galaxies

D thought to be the longest-lived objects in the universe, since they have traveled so far away from us



we suspect that quasars are the active centers of galaxies because

A quasar fuzz produces stellar spectra

B a few quasars have large red shifts

C some quasars fluctuate rapidly

D none of these



if a supermassive black hole drives the nuclear activity of active galaxies, then

A infalling matter forms an accretion disk around it.

B jets can arise from outflows along the spin axis.

C the black hole is probably larger than 1,000 ly in radius.

D (a) and (b).

E (b) and (c).



what observational evidence do we have that quasars are relatively small I size?

A the light output of quasars varies on time scales of days to a few years

B the lines of the quasars' spectra are greatly red shifted

C quasars are barely resolved by optical telescopes

D the radiation output is too intense to be coming from a large object



quasars are thought to be:

A mysterious objects that seem to have no connection with more familiar objects.

B nearby objects that have unknown energy sources.

C very old galaxies.

D very young galaxies.



if quasars obey the Hubble law, then they are

A about as bright as a normal star

B about as bright as a normal galaxy

C much brighter than a normal galaxy

D about as bright as all the galaxies together



which of the following statements is the best direct evidence for the small sizes of quasars

A the red shifts of quasars tend to increase as their apparent diameters decrease

B quasars have actual brightnesses which are considerably larger than those of galaxies

C quasars vary their energy output significantly over relatively short spans of time

D quasars look like ordinary stars in an optical telescope



the _______ quasars lead us to conclude that they are far away.

A odd spectra of

B small size of

C intense radio waves from

D dim light received from

E great red shifts of

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