Deck 13: The Deaths of Stars

Question 1

A white dwarf is composed of

A) hydrogen nuclei and degenerate electrons.
B) helium nuclei and normal electrons.
C) carbon and oxygen nuclei and degenerate electrons.
D) degenerate iron nuclei.
E) a helium burning core and a hydrogen burning shell.

Answer 1

carbon and oxygen nuclei and degenerate electrons.

Question 2

The Algol paradox is explained by considering

A) the degenerate nature of the hydrogen on the surface of the white dwarf.
B) that iron is the most tightly bound of all atomic nuclei.
C) the rate of expansion of the shock wave inside the supernova.
D) the rotation rate of a neutron star.
E) mass transfer between the two stars in a binary system.

Answer 2

mass transfer between the two stars in a binary system.

Question 3

In A.D.1054,Chinese astronomers observed the appearance of a new star,whose location is now occupied by

A) a globular cluster.
B) a planetary nebulae.
C) a white dwarf.
D) a young massive star.
E) a supernova remnant.

Answer 3

a supernova remnant.

Question 4

A Type I supernova is believed to occur when

A) the core of a massive star collapses.
B) carbon detonation occurs.
C) a white dwarf exceeds the Chandrasekhar limit.
D) the cores of massive stars collapse.
E) neutrinos in a massive star become degenerate and form a shock wave that explodes the star.

Question 5

A nova is almost always associated with

A) a very massive star.
B) a very young star.
C) a star undergoing helium flash.
D) a white dwarf in a close binary system.
E) a solar like star that has exhausted its hydrogen and helium.

Question 6

A planetary nebula is

A) the expelled outer envelope of a medium mass star.
B) produced by a supernova explosion.
C) produced by a nova explosion.
D) a nebula within which planets are forming.
E) a cloud of hot gas surrounding a planet.

Question 7

A typical planetary nebula will be visible for about

A) 50 years.
B) 500 years.
C) 50,000 years.
D) 5,000,000 years.
E) 5 billion years.

Question 8

As material leaves an expanding star and begins to fall into a white dwarf

A) an accretion disk will form around the white dwarf.
B) the material will cool off because it begins to move at high velocities.
C) the material will fall directly onto the surface of the white dwarf.
D) the white dwarf will produce a type-II supernova.
E) the white dwarf's radius will increase.

Question 9

A main sequence star of 8.5 solar masses can become a white dwarf by

A) exceeding the Chandrasekhar limit.
B) losing mass.
C) gaining mass.
D) remaining at 8.5 solar masses.

Question 10

The energy a white dwarf emits into space is

A) replaced by fusion of hydrogen atoms into helium.
B) replaced by fusion of helium atoms into carbon.
C) not replaced.

Question 11

We know that the central object in a planetary nebula has a surface temperature of at least ____ because the nebula contains large amounts of ionized hydrogen.

A) 5000 K
B) 10,000 K
C) 15,000 K
D) 20,000 K
E) 25,000 K

Question 12

The Chandrasekhar limit is ____ solar masses.

A) 0.014
B) 0.14
C) 1.4
D) 14

Question 13

As a white dwarf cools its radius does not change because

A) pressure due to nuclear reactions in a shell just below the surface keeps it from collapsing.
B) pressure does not depend on temperature for a white dwarf because the electrons are degenerate.
C) pressure does not depend on temperature because the white dwarf is too hot.
D) pressure does not depend on temperature because the star has exhausted all its nuclear fuels.
E) material accreting onto it from a companion maintains a constant radius.

Question 14

If the theory that novae occur in close binary systems is correct,then novae should

A) produce synchrotron radiation.
B) occur in regions of star formation.
C) not occur in old star clusters.
D) all be visual binaries.
E) repeat after some interval.

Question 15

The Helix and Egg nebulae are

A) supernova remnants.
B) planetary nebulae.
C) the result of carbon detonation.
D) the result of the collapse of the iron core of each star.
E) nebulae associated with Herbig-Haro objects.

Question 16

When material expanding away from a star in a binary system reaches the Roche surface

A) the material will start to fall back toward the star.
B) all of the material will accrete onto the companion.
C) the material is no longer gravitationally bound to the star.
D) the material will increase in temperature and eventually undergo thermonuclear fusion.
E) c and d

Question 17

Suppose that a planetary nebula is 0.5 parsecs in diameter and expanding at 20 km/s.How old is it? (Hint: 1 pc = 3.1*10¹³ km.)

A) 25,000 years
B) 12,000 years
C) 6,000 years
D) 49,000 years
E) 100,000 years

Question 18

The Chandrasekhar limit tells us that

A) accretion disks can grow hot through friction.
B) neutron stars of more than 3 solar masses are not stable.
C) white dwarfs must contain more than 1.4 solar masses.
D) not all stars will end up as white dwarfs.
E) stars with a mass less than 0.5 solar masses will not go through helium flash.

Question 19

The lowest-mass stars cannot become giants because

A) they do not contain helium.
B) they rotate too slowly.
C) they cannot heat their centers hot enough.
D) they contain strong magnetic fields.
E) they never use up their hydrogen.

Question 20

A planetary nebula

A) produces an absorption spectrum.
B) produces an emission spectrum.
C) is contracting to form planets.
D) is contracting to form the star.
E) is the result of carbon detonation in a 1.

Question 21

A supernova remnant is expanding in radius at the rate of 0.5 seconds of arc per year.Doppler shifts show that the velocity of expansion is 5700 km/sec.How far away is the supernova remnant?

A) 1140 pc
B) 11,400 km
C) 5700 pc
D) 24 pc
E) 2400 pc

Question 22

A white dwarf star is prevented from collapsing by

A) nuclear energy it is generating
B) its gravitational force
C) Hubble's law of extragalactic redshifts
D) degenerate electron gas pressure
E) degenerate astronomers observing the star

Question 23

Massive stars cannot generate energy through iron fusion because

A) iron fusion requires very high density.
B) stars contain very little iron.
C) no star can get hot enough for iron fusion.
D) iron is the most tightly bound of all nuclei.
E) massive stars supernova before they create an iron core.

Question 24

The diagram below shows a light curve from a supernova.How many days after maximum light did it take for the supernova to decrease in brightness by a factor of 100?

A) 25
B) 50
C) 100
D) 150
E) 250

Question 25

Before it ejects a planetary nebula,a star is a

A) red giant
B) black hole
C) white dwarf
D) super nova

Question 26

What are the two longest stages in the life of a one solar mass star?

A) Protostar,pre-main sequence.
B) Protostar,white dwarf.
C) Protostar,main-sequence.
D) Main-sequence,white dwarf.

Question 27

For a star of Sun-like mass,what is the last stage of the nuclear fusion?

A) Hydrogen to helium.
B) Helium to carbon and oxygen.
C) Carbon to magnesium.
D) Fusion goes all the way up to iron.

Question 28

A type-II supernova

A) occurs when a white dwarf's mass exceeds the Chandrasekhar limit.
B) is the result of helium flash.
C) is characterized by a spectrum that shows hydrogen lines.
D) occurs when the iron core of a massive star collapses.
E) c and d

Question 29

Stars that have ejected a planetary nebula eventually become

A) protostars.
B) brown dwarfs.
C) white dwarfs.
D) red giants.

Question 30

The central star in a planetary nebula ...

A) is a main sequence star
B) is a pre-main sequence proto-star
C) is a neutron star
D) will become a white dwarf

Question 31

The explosion of a supernova typically leaves behind

A) a planetary nebula.
B) a shell of hot,expanding gas with a white dwarf at the center.
C) a shell of hot,expanding gas with a pulsar at the center.
D) nothing is ever left behind.

Question 32

The theory that the collapse of a massive star's iron core produces neutrinos was supported by

A) the size and structure of the Crab nebula.
B) laboratory measurements of the mass of the neutrino.
C) calculation of models of core collapse.
D) underground counts from solar neutrinos.
E) the detection of neutrinos from the supernova of 1987.

Question 33

Synchrotron radiation is produced by

A) objects with temperatures below 10,000 K.
B) high-velocity electrons moving through a magnetic field.
C) cold hydrogen atoms in space.
D) the collapsing cores of massive stars.
E) helium flash.

Question 34

Stars with masses between 0.4 and 4

A) undergo thermonuclear fusion of hydrogen and helium,but never get hot enough to ignite carbon.
B) undergo thermonuclear fusion of hydrogen,but never get hot enough to ignite helium.
C) produce type-I supernovae after they exhaust their nuclear fuels.
D) produce type-II supernovae after they exhaust their nuclear fuels.
E) undergo carbon detonation.

Question 35

The image shows the Crab Nebula.The Crab Nebula is

A) a planetary nebula
B) a name for the cloud of gas and dust which later became our solar system
C) a ejected cloud of gas from a super nova
D) in the constellation Orion,containing many bright young blue stars

Question 36

White dwarf stars are formed from

A) the most massive main sequence stars
B) lower mass main sequence stars
C) A main sequence star stays a main sequence star forever.
D) Main sequence stars are formed from white dwarf stars.

Question 37

Where are elements heavier than iron primarily produced?

A) Brown dwarfs
B) White dwarfs
C) Supergiants
D) Supernovae

Question 38

Synchrotron radiation is produced

A) in planetary nebulae.
B) by red dwarfs.
C) by massive stars as their iron core collapses.
D) in supernova remnants.
E) by neutrinos.

Question 39

After what evolutionary stage does a star become a white dwarf?

A) Protostar
B) Pre-main sequence
C) Main sequence
D) Giant

Question 40

What mechanism does an isolated white dwarf use to generate energy?

A) Proton-proton chain
B) CNO cycle
C) Triple alpha process
D) White dwarfs don't generate their own energy.

Question 41

Planetary nebulae are sites of planet formation.

Question 42

Stars less massive than 0.4 solar mass never become giant stars.

Question 43

The sun will eventually become a supernova.

Question 44

Because massive stars have more gravitational energy than the sun,they can fuse heavier nuclear fuels.

Question 45

Synchrotron radiation occurs when high speed electrons move through a magnetic field.

Question 46

A star begins fusing hydrogen to helium the moment it leaves the main sequence.

Question 47

Electrons moving in a strong magnetic field emit ____________________ radiation.

Question 48

A white dwarf whose red giant companion dumps hydrogen onto it may

A) show no effect.
B) explode recurrently as a nova.
C) blow up as a type I supernova.
D) answers b or

Question 49

Mass can flow from one star in a binary system to its companion through the first ____________________ point.

Question 50

A(n)____________________ is the sudden expulsion of the outer layers of a moderate mass star that has a dormant carbon core.

Question 51

A(n)____________________ supernova is caused by the collapse of a massive star that has lost its outer envelope of hydrogen.

Question 52

____________________ are caused by periodic eruptions in the helium fusion shell and may provide the energy to eject the material that forms a planetary nebula.

Question 53

No known white dwarf has a mass greater than the Chandrasekhar limit.

Question 54

A nova destroys the star and leaves behind a white dwarf.

Question 55

An accretion disk can grow hot enough to radiate X-rays.

Question 56

A Type II supernova produces a planetary nebula.

Question 57

The average size of a white dwarf is about the same size as the Earth.

Question 58

Type II supernovae are believed to occur when the core of a massive star collapses.

Question 59

Once a star ejects a planetary nebula,it becomes a white dwarf.