Test 3

Front 1

In the core of a main sequence star, gas pressure _____ the weight of the overlying materials.
a. is less than
b. is greater than
c. balances

Back 1

c. balances

Front 2

Energy can flow outward from the cores of different kinds of stars by
a. conduction
b. convection
c. radiation
d. all of the above

Back 2

d. all of the above

Front 3

The main sequence has a limit at the lower end because
a. low mass stars form from the interstellar medium very rarely.
b. hydrogen fusion combined 4 hydrogen nuclei to form 1 helium nucleus.
c. pressure does not depend on temperature in degenerate matter.
d. the lower limit represents when the radius of the star would be zero.
e. there is a minimum temperature for hydrogen fusion.

Back 3

e. there is a minimum temperature for hydrogen fusion.

Front 4

The lowest mass object that can initiate thermonuclear fusion of hydrogen has a mass of about
a. 1 M
b. 60 M
c. 0.5 M
d. 0.08 M
e. 0.001 M

Back 4

d. 0.08 M

Front 5

As a star like the sun exhausts hydrogen in its core, the outer layers of the star
a. become hotter and more luminous.
b. become cooler and more luminous.
c. become hotter and less luminous.
d. become cooler and less luminous.
e. become larger in radius and hotter.

Back 5

b. become cooler and more luminous.

Front 6

Giant and supergiant stars are rare because
a. they do not form as often as main sequence stars.
b the giant and supergiant stage is unstable.
c. the giant and supergiant stage is very short.
d. helium is very rare.
e. helium flash destroys many of the stars before they can become giants and supergiants.

Back 6

c. the giant and supergiant stage is very short.

Front 7

Which of the following nuclear fuels does a one solar mass star use over the course of its entire evolution?
a. hydrogen
b. hydrogen and helium
c. hydrogen, helium, and carbon
d. hydrogen, helium, carbon, and neon
e. hydrogen, helium, carbon, neon, and oxygen

Back 7

b. hydrogen and helium

Front 8

Which of the following nuclear fuels does a 0.2 solar mass star (red dwarf) use over the course of its entire
evolution?
a. hydrogen
b. hydrogen and helium
c. hydrogen, helium, and carbon
d. hydrogen, helium, carbon, and neon
e. hydrogen, helium, carbon, neon, and oxygen

Back 8

a. hydrogen

Front 9

In the diagram above, which position would indicate that of the Sun as it approaches end of hydrogen burning in its core?
a. 1
b. 2
c. 3
d. 4
e. 5

Back 9

d. 4

Front 10

In the diagram above, locate the position of our Sun after it has commenced helium burning and has become a
red giant.
a. 1
b. 2
c. 3
d. 4
e. 5

Back 10

e. 5

Front 11

In the diagram above locate the position of red dwarf stars that will never burning elements heavier than
hydrogen in their cores.
a. 1
b. 2
c. 3
d. 4
e. 5

Back 11

c. 3

Front 12

Open clusters tend to be __________________ than globular clusters.
a. younger and contain fewer stars
b. younger and contain more stars
c. older and contain fewer stars
d. older and contain more stars
e. more luminous and cooler

Back 12

a. younger and contain fewer stars

Front 13

What must occur for an object to be considered a main sequence star?
a. Hydrostatic equilibrium
b. Nuclear fusion reaction in the core
c.. Protostar life begins
d. Both a and b.

Back 13

d. Both a and b.

Front 14

Why do higher mass stars live shorter lives on the main sequence than lower mass stars?
a. Higher mass stars burn through their nuclear fuel faster.
b. Lower mass stars don’t get their energy from that same nuclear fusion source as higher mass stars.
c. Higher mass stars have less hydrogen fuel to burn.
d. Lower mass stars spend a longer time evolving to the main-sequence.
e. All of the above are false.

Back 14

a. Higher mass stars burn through their nuclear fuel faster.

Front 15

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.

Back 15

c. they cannot heat their centers hot enough.

Front 16

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.

Back 16

a. the expelled outer envelope of a medium mass star.

Front 17

A white dwarf is composed of
a. hydrogen nuclei and degenerate electrons.
b. helium nuclei and normal electrons.
c. degenerate matter..
d. degenerate iron nuclei.
e. a helium burning core and a hydrogen burning shell.

Back 17

c. degenerate matter..

Front 18

The Chandrasekhar limit is ________ solar masses.
a. 0.014
b. 0.14
c. 1.4
d. 14

Back 18

c. 1.4

Front 19

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.

Back 19

d. a white dwarf in a close binary system.

Front 20

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.

Back 20

a. an accretion disk will form around the white dwarf.

Front 21

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.

Back 21

e. repeat after some interval.

Front 22

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.

Back 22

e. a supernova remnant.

Front 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.

Back 23

d. iron is the most tightly bound of all nuclei.

Front 24

Sun-like stars with masses between 0.4 M and 4 M
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.

Back 24

a. undergo thermonuclear fusion of hydrogen and helium, but never get hot enough to ignite carbon.

Front 25

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.

Back 25

b. Helium to carbon and oxygen.

Front 26

Stars that have ejected a planetary nebula eventually become
a. protostars.
b. brown dwarfs.
c. white dwarfs.
d. red giants.

Back 26

c. white dwarfs.

Front 27

After what evolutionary stage does a star become a white dwarf?
a. Protostar
b. Pre-main sequence
c. Main sequence
d. Giant

Back 27

d. Giant

Front 28

The explosion of a supernova typically leaves behind
a. a dark nebula.
b. a shell of hot, expanding gas with a brown dwarf at the center.
c. a shell of hot, expanding gas with a pulsar at the center.
d. nothing is ever left behind.

Back 28

c. a shell of hot, expanding gas with a pulsar at the center.

Front 29

Planetary nebulae are sites of planet formation.
True or False

Back 29

False

Front 30

The sun will eventually become a supernova.
True or False

Back 30

False

Front 31

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

Back 31

False

Front 32

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

Back 32

True

Front 33

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

Back 33

True

Front 34

The average size of a white dwarf is about the same size as the Earth
True or False

Back 34

True

Front 35

We expect neutron stars to spin rapidly because they conserve angular momentum.
True or False

Back 35

True

Front 36

Pulsars could not be pulsating stars because the pulses are too short.
True or False

Back 36

True

Front 37

If the accretion disk around a black hole emits x-rays outside the event horizon, then the x-rays can escape.
True or False

Back 37

True

Front 38

Rotating black holes are called Kerr black holes.
True or False

Back 38

True

Front 39

When a star, of mass comparable to the Sun, dies it become a black hole.
True or False

Back 39

False

Front 40

The density of a _________ is greater than the density of a ____________.
a. white dwarf, neutron star
b. neutron star, black hole
c. pulsar, neutron star
d. pulsar, white dwarf
e. white dwarf, black hole

Back 40

d. pulsar, white dwarf

Front 41

The center of our galaxy lies in the direction of the constellation of
a. Ursa Minor.
b. Ursa Major.
c. Sagittarius.
d. Orion.
e. Monoceros.

Back 41

c. Sagittarius.

Front 42

Younger stars have more heavy elements because
a. old stars destroy heavy elements as they age.
b. young stars burn their nuclear fuels faster.
c. heavy elements were made in previous generations of stars.
d. all of the above
e. heavy elements haven't had time to settle to the core of these younger stars.

Back 42

c. heavy elements were made in previous generations of stars.

Front 43

43. Population II stars
I. are primarily found in the disk of the galaxy.
II. contain more heavy metals than population I stars.
III. are primarily old low mass stars.
IV. are located in globular clusters.
a. III & IV
b. I & II
c. II
d. IV
e. I, II, & III

Back 43

a. III & IV

Front 44

The age of the Milky Way galaxy has been estimated to be at least 13 billion years based on
a. observations of globular clusters.
b. observations of open clusters.
c. 21-cm radiation from H I regions.
d. the rotation curve of the galaxy.
e. the energy produced by Sagittarius A*

Back 44

a. observations of globular clusters.

Front 45

The nuclear bulge of our galaxy
a. contains stars that are primarily population I stars.
b. contains relatively large amounts of gas and dust.
c. contains stars primarily associated with the spherical component of our galaxy.
d. contains stars primarily associated with the disk component of our galaxy.
e. a, b and d

Back 45

c. contains stars primarily associated with the spherical component of our galaxy.

Front 46

The orbits of population I stars
I. are confined to disk of the galaxy.
II. are very elliptical.
III. are nearly circular.
IV. are randomly inclined to the disk of the galaxy.
a. I
b. IV
c. I & IV
d. II & IV
e. I & III

Back 46

e. I & III

Front 47

The traditional theory for the formation of the Milky Way Galaxy suggests that the galaxy formed
a. as material accreted around a massive black hole currently at the center of our galaxy.
b. from a large cloud of material that formed stars and star clusters and slowly flattened
to a disk.
c. from material that had been ejected in the violent explosion of a dying galaxy.
d. as a result of mergers between several smaller groups of gas, dust, and stars.
e. as two massive galaxies collided.

Back 47

b. from a large cloud of material that formed stars and star clusters and slowly flattened
to a disk.

Front 48

Radio maps of our galaxy show spiral arms because the
a. arms have high Doppler shifts.
b. gas in the spiral arms is hot enough to emit photons.
c. dust in spiral arms is more dense than it is between the spiral arms.
d. hydrogen gas in spiral arms is more dense than it is between the spiral arms.
e. stars in the spiral arms emit most of their energy at radio wavelengths.

Back 48

d. hydrogen gas in spiral arms is more dense than it is between the spiral arms.

Front 49

A several million solar mass ___________ is thought to be at the center of our galaxy.
a. spiral arm
b. globular cluster
c. planet
d. black hole

Back 49

d. black hole

Front 50

The energy source at the center of our galaxy is called
a. Cygnus X-1.
b. the Orion arm.
c. the sun.
d. Sagittarius A*.

Back 50

d. Sagittarius A*.

Front 51

Since Red Dwarf stars are so small and have so little fuel, they have the shortest lifetimes.

Back 51

b. False

Front 52

The greater the luminosity of a Cepheid Variable star the shorter the period.

Back 52

b. False

Front 53

Planetary nebulae are sites of planet formation

Back 53

b. False

Front 54

Pulsars have been discovered with planets orbiting them.

Back 54

A. True

Front 55

The dis of the Milky Way is approximately 20,000 light-years in diameter.

Back 55

B. False