White Dwarfs





as a degenerate gas is heated, it will

A expand

B contract

C neither expand nor contract

D oscillate



a planetary nebula is

A the vastly expanded shell of a dying star.

B a cloud of gas out of which stars form.

C a cloud of cold dust in space.

D the same as a white dwarf.

E a circular ring around a black hole.



inside a white dwarf electrons are stripped from atoms because

A of the high temperature

B of the great density

C the nuclear furnace has turned off

D it is becoming a neutron star



in a degenerate electron gas the outward pressure which keeps the star fro collapsing is

A dependent upon temperature

B dependent upon mass

C independent of temperature

D independent of mass



one of the causes for the phenomenon called a nova is

A the fusion of iron in the core of a massive star.

B the in fall of material onto a neutron star from a white dwarf.

C the transfer of material onto a white dwarf in a double star system.

D the collapse of a proto star.

E the death of a massive star and the formation of a black hole.



a planetary nebula is

A a shell of ejected gases, glowing from light from a central star

B the formation stages of planets around other stars than the sun

C a gas cloud surrounding a planet

D the cloud of gas produced by a supernova explosion



a planetary nebula is

A dust and gas orbiting a planet far from its surface.

B dust and gas orbiting close to a planet's surface.

C gas blown off a dying star.



which of the following is the last stage in the life of a low mass star?

A the crab nebula.

B a cepheid variable.

C a dark nebula.

D a pulsar.

E none of the above.



a nova is associated with

A a giant star with a degenerate core

B a white dwarf in a close binary system

C a white dwarf that exceeds 1.4 solar masses

D a star with an iron core



all novae are thought to involve a

A white dwarf

B main sequence star

C supergiant

D neutron star



when the sun "dies" it will become a

A supernova

B neutron star

C white dwarf

D black hole



according to our present theories, when our sun "dies," what will it become

A a white dwarf

B a black hole

C a supernova

D a red giant



the Pauli exclusion principle says that

A no two stars can be in the same place on the H-R diagram

B a star cannot fuse more than one type of nucleus at a time

C when a perfect gas expands, it has to cool

D two subatomic particles can't occupy the same quantum state



a white dwarf is dense, meaning it has a

A great mass

B solid core

C great mass for its volume

D great opacity



the stellar remnant of a one solar mass star is a

A white dwarf

B neutron star

C pulsar

D black hole



the density of white dwarf stars, compared to the sun's is

A lower

B about the same

C somewhat greater

D much greater



which is not true of white dwarfs:

A they are infrequently seen because stars in the appropriate range of mass are rare in our galaxy

B they are infrequently seen because stars in the appropriate range of massage very slowly

C they are infrequently seen because their actual brightness is very low

D they are roughly the size of the Earth?



all novae we have observed are thought to be

A red stars

B cepheids

C close binaries

D pulsars



why are all known white dwarfs relatively close to the sun.

A white dwarfs are only formed in our neighborhood of the galaxy.

B light from distant white dwarfs has not yet reached the Earth.

C no white dwarfs are bright enough to be seen at great distances.

D light from distant white dwarfs is too red shifted to be seen.

E the statement is false; white dwarfs are seen at all distances from the sun.



a nova explosion could be

A a small-scale supernova explosion

B the source of the "crab nebula"

C a temporary spate of fusion reactions on the surface of a white dwarf star in a binary system

D a temporary spate of fusion reactions on the surface of a solitary white dwarf star



white dwarf stars are extremely faint because they are

A young

B old

C too small to have nuclear reactions

D too hot to emit visible light



when stars less massive than one and a half times the sun die, they become

A supernovae

B novae

C black holes

D white dwarfs



astronomers now believe that a nova is caused by

A the fusion of iron in the core of a massive star

B the in fall of material onto a neutron star

C the transfer of material onto a white dwarf in a double star system

D the death of a massive star and the formation of a black hole



when a star less massive than the sun has consumed all of its nuclear fuel, it becomes a

A white dwarf

B nova

C supernova

D black hole.



whether a star becomes a white dwarf, a neutron star, or a black hole depends on its

A mass

B metal abundance

C helium abundance

D apparent brightness



what is the difference between the sun and a one-solar-mass white dwarf?

A the sun is larger.

B the sun has more hydrogen.

C they have different energy sources.

D all of the above.

E none of the above.



the term "nova" means new. a nova is usually associated with

A proto stars

B main-sequence stars

C older stars in a binary system

D star death



all novae are

A red stars

B cepheids

C sites for the formation of pulsars

D close binaries



a star with a mass of less than 1.4 solar masses will probably end its life as a

A white dwarf.

B neutron star.

C black hole.

D pulsar.



a white dwarf is approximately the same size as

A the sun

B a neutron star

C the Earth

D a large building



a low mass main sequence star will, at death, be a

A black hole

B white dwarf

C neutron star

D supernova



if novas occur in close binary star systems, the source of the nova outburst is

A the collision of the two stars.

B the in fall of matter on the more highly evolved star.

C the explosion of the less highly evolved star.

D the start of helium burning in both stars.



which of the following in not a type of "dead" star

A pulsar

B the sun

C black hole

D white dwarf



novae explosions are caused by

A exploding white dwarfs

B interstellar matter falling onto the surface of a star, usually a white dwarf

C material falling into a black hole

D mass lost from a normal star falling onto a white dwarf companion



the probable fate of our sun is

A to expand as a red giant, undergo a nova outburst and end as a white dwarf

B to expand as a red giant, eventually become a planetary nebula, and end as a white dwarf

C expand, undergo a helium flash, become variable, and eventually to explode as a supernova

D to become a black hole



at some time in its lifetime, the sun will become a

A white dwarf

B blue supergiant

C neutron star

D black hole



immediately after all the hydrogen in the core is used up a 1mo star becomes

A Joan Jett

B a supernova

C a red giant

D a white dwarf



a white dwarf is relatively stable because

A gravity is no longer as strong as it was

B powerful reactions release energy to counterbalance gravity

C the rigid structure of the electrons resists further compression

D matter simply can't be compressed anymore



our sun's destiny is to become

A a supernova

B a white dwarf

C a blue giant

D a neutron star



a white dwarf star is at what stage of its evolution?

A main sequence phase, "middle-aged"

B post-supernova stage, after the explosion of a star

C proto star phase, just after formation

D very late phase of evolution



a white dwarf, compared to a main sequence star of the same mass, would be

A larger in radius

B smaller in radius

C younger

D lower in surface temperature



astronomers believe that our sun will someday become

A a red giant

B the source of a planetary nebula

C a white dwarf

D all of the above



which physical phenomenon keeps a white dwarf star from collapsing inwards upon itself?

A the physical size of the neutrons

B normal gas pressure

C convection currents or updrafts from the nuclear furnace

D electron degeneracy



at which phase of its evolutionary life is a white dwarf star?

A very late for small mass star, in dying phase

B post-supernova phase, the remnant of the explosion

C just at main sequence phase

D early phases, soon after formation



white dwarf stars are generating energy by the

A proton-proton process

B carbon cycle

C triple alpha process

D none of the above



the name "white dwarf" indicates that a star is

A hot and large

B cool and large

C cool and small

D hot and small



white dwarfs cannot be more massive than _____ solar masses

A 0.4

B 1.0

C 1.4

D 2.4



which of the following have diameters of about 10,000 miles

A black holes

B neutron stars

C supernovas

D white dwarfs



stars most frequently die when they

A are unable to sustain high enough temperatures for the next nuclear fuel

B run out of all nuclear fuels

C become so hot they explode

D lose all their matter to slow evaporation into space



at the end of its evolution, our sun will become

A a main sequence star

B a white dwarf

C a pulsar (or neutron star)

D a black hole



the mass of a white dwarf

A is greater than 4 solar masses

B is always much less than the mass of the original star

C is greater than the mass of the original main-sequence star

D is less than 1 solar masses



which of the following is not true of white dwarfs

A they are about the size of the Earth

B they are usually hotter than the sun

C they will eventually explode

D they are much fainter than the sun



white dwarf stars are

A young faint stars on the way to the main sequence

B old dead stars

C small stars whose mass is too low to ever reach the main sequence

D bright, hot stars with most of their radiation falling outside the visible region of the spectrum



when a star dies, it immediately

A explodes

B expands

C contracts

D stops shining



in degenerate matter

A pressure depends only on temperature

B temperature depends only on density

C pressure does not depend on temperature

D none of these



which is the correct sequence for the following end-points of stellar evolution, in order of increasing mass?

A black hole, neutron star, white dwarf

B neutron star, black hole, white dwarf

C white dwarf, black hole, neutron star

D white dwarf, neutron star, black hole



the collapse of a white dwarf is stopped when

A a new source of energy becomes active

B the electrons become degenerate

C the heat inside the star becomes intense enough

D the electrons combine with the protons to form neutrons



matter ejected by a dying low-mass star is called a

A supernova remnant

B diffuse nebula

C planetary nebula

D herbig-haro objects



a white dwarf star is about the same size as

A new york city

B the sun

C the Earth

D the total solar system



will the sun become a white dwarf?

A yes, but only after it explodes as a supernova

B no, because the sun will remain a red giant star indefinitely

C yes, once it has passed through its red-giant phase

D no, because the sun has too much mass to become a white dwarf



a star was found to have the size of the Earth and the mass of the sun. it was undoubtedly a

A red dwarf

B white dwarf

C super giant

D nova



1.5 solar masses is the upper limit on the masses of

A black holes

B supergiants

C neutron stars

D white dwarfs



a star having a core with less than 1.4 solar masses will end its life as a

A white dwarf.

B black hole.

C neutron star.

D pulsar.



a white dwarf is generating its energy from what source?

A nuclear fusion of hydrogen

B it no longer generates energy, but is just cooling down

C nuclear fission of heavy elements

D gravitational contraction



electron "degeneracy" (in astronomy and physics) is a term used to

A describe conditions during a supernova explosion

B describe conditions within a black hole

C describe matter which is prevented from shrinking due to the rules electrons must obey when packed close together

D describe the outer regions of a red giant star



a star with a mass of less than 1.4 solar masses will probably end its life as a

A white dwarf

B neutron star

C black hole

D pulsar



gravity cannot collapse a white dwarf star because

A the un-ionized atoms of the star are in contact

B fusion prevents any contraction

C electron degeneracy counteracts gravity

D the star's core is too hot



at what stage of its life will our sun become a neutron star?

A right after the main sequence

B right after the red giant stage

C right after it gives off a planetary nebula

D you can't fool me; the sun will never become a neutron star



the fate of an isolated white dwarf is

A to eventually collapse to become a neutron star

B to eject a shell of material and become a planetary nebula

C to explode as a supernova

D to cool until it no longer emits enough light to be seen



a typical white dwarf star:

A has a mass about like that of the sun and is about half the sun's diameter.

B has a mass slightly less than that of the sun and is about the size of the Earth.

C has a mass about a hundredth that of the sun and is about the size of the Earth.

D is so small and insignificant that none will likely ever by observed by astronomers.



white dwarfs are

A cold and heavy

B hot and dense

C luminous and magnetic

D bright and active



in the cores of stars that have ceased their nuclear fusion processes a state can develop where all low energy electron states are filled. then only high velocity, high energy states are available to the remaining electrons. this state is called:

A photo disintegration.

B the chandrasekhar limit.

C the helium flash.

D electron degeneracy.



synchrotron radiation is observed from

A black holes

B pulsars

C supernovae

D ordinary stars.



a star which contracts to one half its original size will be rotating

A at the same rate as before

B at the previous rate

C at 1/4 the previous rate

D at 4 times the previous rate



since the crab nebulae is so young (1000 yrs.) it must be

A small

B expanding rapidly

C very dense

D no choice



the material of a planetary nebulae is

A escaping from the central star

B falling onto the central star

C neither (a) nor (b)

D no choice



to produce detectable synchrotron radiation one must have both high energy free electrons and

A an intense gravitational field

B an intense electrical field

C an intense magnetic field

D superheavy nuclei



the radiation observed from neutron stars is primarily

A x-rays

B infrared

C synchrotron

D gravity waves



the velocity of expansion of the crab nebula is

A about 1000 mi/sec

B too small to be detected

C nearly the speed of light

D randomly different for different parts of the nebula



Return to Table of Contents