Deck 11: The Deaths of Stars

Question 1

____ is a form of electromagnetic radiation produced by rapidly moving electrons spiraling through magnetic fields.

A) Lagrangian radiation
B) Accretion
C) Ultraviolet radiation
D) Synchrotron radiation
E) Infrared radiation

Answer 1

Synchrotron radiation

Question 2

In star clusters, the ____ stars are giant stars fusing helium in their cores and then in their shells.

A) turnoff point
B) main sequence
C) turnon point
D) hydrogen flash
E) horizontal branch

Answer 2

horizontal branch

Question 3

The ____________ are places in the orbital plane of a binary star system where a bit of matter can reach stability. The one located directly between the two stars is the point where the Roche lobes meet.

A) turnoff points
B) horizontal branch
C) Lagrangian points
D) synchrotron points
E) radiation belts

Answer 3

Lagrangian points

Question 4

In the diagram below, which point indicates the location on the HR diagram of a one solar mass star when it undergoes helium flash?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 5

A(n) ____ is a collection of 10⁵ to 10 ⁶ stars in a region 10 to 30 pc in diameter. The stars in the collection tend to be more than 10 9 years old and mostly yellow and red stars.

A) Herbig Haro object
B) globular cluster
C) open cluster
D) giant cluster
E) supernova

Question 6

As a star exhausts hydrogen in its core, it

A) becomes hotter and more luminous
B) becomes hotter and less luminous
C) becomes cooler and less luminous
D) becomes larger in radius and hotter

Question 7

Stars in a star cluster

A) all have the same age.
B) all have the same chemical composition.
C) all have the same luminosity.
D) all of the above
E) a and b above

Question 8

Helium flash occurs

A) because helium is very explosive and cannot be controlled when the nuclear reactions occur.
B) because degenerate electrons in the core do not allow the core to expand as it heats up.
C) in Cepheid variables.
D) in stars with masses less than 0.4 M.
E) none of the above

Question 9

The triple alpha process

A) controls the pulsations in Cepheid variable stars.
B) is the nuclear fusion of hydrogen to helium in massive stars.
C) is the process that produces the neutrinos we receive from the sun.
D) requires a temperature of about 5,000,000 K to operate
E) occurs during helium flash.

Question 10

A mass is transferred through the inner Langragria point in a binary system toward a white dwarf, the material forms a rapidly growing whirlpool of material known as a(n)

A) accretion disk.
B) Lagrangian point.
C) Algol paradox.
D) planetary nebula.
E) supernova remnant.

Question 11

A(n) ____ is a collection of 100 to 1000 stars in a region about 25 pc in diameter. The stars in the collection are typically quite young.

A) Herbig Haro object
B) globular cluster
C) open cluster
D) giant cluster
E) supernova

Question 12

Stars within a cluster that are at the turnoff point

A) have life expectancies that are equal to the age of the cluster.
B) are stars that are just becoming white dwarfs.
C) are stars that are just entering the main sequence portion of their evolution.
D) are stars that are about to supernova.
E) are stars that are generally spectral type G stars.

Question 13

Giant and supergiant stars are rare because

A) they do not form as often as main sequence stars.
B) the star blows up before the giant or supergiant stage is reached
C) the giant or supergiant stage is very short.
D) the giant or supergaint stage is very long

Question 14

In degenerate matter

A) pressure depends only on the temperature.
B) temperature depends only on density.
C) pressure does not depend on temperature.
D) pressure does not depend on density.
E) b and c

Question 15

A star will experience a helium flash if

A) it is less massive than about 3 solar masses
B) its has become a red giant star
C) its has formed a helium core
D) the material in the core has gradually become degenerate
E) All of the above must be true.

Question 16

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.

Question 17

If the stars at the turnoff point of a cluster have a mass of 3 M , what is the age of the cluster?

A) 3.0*10¹⁰ years
B) 3.3*10⁹ years
C) 6.4*10⁸ years
D) 1.6*10¹¹ years
E) The age of a star cluster can not be determined from the mass of stars at the turnoff point.

Question 18

The Crab nebula is

A) a planetary nebula.
B) a Bok globule.
C) an open cluster.
D) an absorption nebula.
E) supernova remnant.

Question 19

Star clusters are important to our study of stars because

A) all stars formed in star clusters.
B) the sun was once a member of a globular cluster.
C) they give us a method to test the our theories and models of stellar evolution.
D) they are the only objects that contain Cepheid variables.
E) all of the above

Question 20

What is the approximate age of the star cluster in the HR diagram below? (Hint: Main Sequence Stars of spectral between types A and B core supply of hydrogen is sufficient to last about 250 million years. Between A and F about 2 billion years. Type G about 10 billion years. Between K and M about 30 billion years..)

A) 200 million years
B) 2 billion years
C) 10 billion years
D) 30 billion years
E) The age of the cluster can not be estimated from an HR diagram of the cluster.

Question 21

A planetary nebula

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

Question 22

The Algol paradox is explained by considering

A) the degenerate nature of the hydrogen on the surface of the white dwarf.
B) synchrotron radiation
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.

Question 23

Synchrotron radiation is produced

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

Question 24

About how long will a 0.5 star spend on the main sequence?

A) 5 billion years
B) 57 billion years
C) 570 million years
D) 5 million years
E) 500 thousand years

Question 25

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) less than 50
B) 50
C) 150
D) 250
E) more than 250

Question 26

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 on to the companion.
C) the material is no longer gravitationally bound to the star.
D) the material will increase in temperature an eventually undergo thermonuclear fusion.
E) c and d

Question 27

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 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

A planetary nebula has a radius of 0.5 pc and is expanding at 20 km/sec. What is the approximate age of this planetary nebula? (1 pc is equal to 3*10¹³km and 1 year is equal to 3.15*10⁷seconds.)

A) 240 years
B) 790,000 years
C) 96,000 years
D) 960 years
E) 24,000 years

Question 30

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 31

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 more massive than 1.4 solar masses are not stable.
D) stars cannot travel through space too fast
E) stars with a mass less than 0.5 solar masses will not go through helium flash.

Question 32

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 33

Synchrotron radiation is produced by

A) objects with temperature 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

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 36

A Type I supernova is believed to occur when

A) the core of a massive star collapses.
B) hydrogen 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 37

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) the brightening of supernovae a few days after they are first visible
D) underground counts from solar neutrinos.
E) the detection of neutrinos from the supernova of 1987.

Question 38

As a white dwarf cools its radius will 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 39

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.

Question 40

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) both fusion or fission of iron nuclei absorb energy
E) massive stars supernova before they create an iron core.

Question 41

Pulsars cannot be spinning white dwarfs because

A) white dwarfs are not that common.
B) white dwarfs are not dense enough.
C) white dwarfs do not have magnetic fields.
D) a white dwarf spinning that fast would fly apart.
E) all of the above

Question 42

The ____________ of a black hole is the radius from a black hole at which the escape velocity is approximately equal to the speed of light.

A) Roche limit
B) Lagrangian point
C) Chandraskhar limit
D) Hubble radius
E) event horizon

Question 43

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 44

A neutron star is expected to spin rapidly because

A) they conserved angular momentum when they collapsed.
B) they have high orbital velocities.
C) they have high densities.
D) they have high temperatures.
E) the energy from the supernova explosion that formed them made them spin faster.

Question 45

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

A) a pulsar.
B) a neutron star.
C) a supernova remnant.
D) all of the above

Question 46

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

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

Question 47

Hypernovae are

A) supernovae that occur when two red dwarfs collide.
B) supernovae that occur when 10 solar mass stars explode.
C) supernovae that occur when stars more massive than 25 solar masses explode.
D) one theory to explain the production of gamma ray bursters.
E) both c and d above

Question 48

Pulsars rotations are believed to slow down because

A) they are losing angular momentum into space via outward streaming particles
B) they are dragging companions stars around in their magnetic field.
C) they are getting tired
D) of conservation of angular momentum.
E) their mass is increasing.

Question 49

Although neutron stars are very hot, they are faint and not easy to see at visual wavelengths because

A) light does not escape from their event horizon.
B) most lie beyond dense dust clouds.
C) they have only a small surface area from which to emit.
D) the peak of their thermal emission is at much shorter wavelengths than visual
E) both c and d

Question 50

What nuclear fusion 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 51

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 52

The density of a neutron star is

A) about the same as that of a white dwarf.
B) about the same as that of the sun.
C) about the same as an atomic nucleus.
D) zero

Question 53

Stars that have ejected a planetary nebula eventually become

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

Question 54

___________ are neutron stars that have magnetic fields 100 times stronger than the average neutron star.

A) Hypernovae
B) Collapsars
C) Pulsars
D) Kerr singularities
E) Magnetars

Question 55

____ occurs when light travels out of a gravitational field, loses energy and its wavelength grows longer.

A) A gravitational blue shift
B) The solar wind
C) A gravitational redshift
D) A X-ray burst
E) A pulsar wind

Question 56

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 57

A _____________ has a radius of about 10 km and is supported by the pressure associated with degenerate neutrons.

A) black hole
B) neutron star
C) white dwarf
D) supernova remnant
E) red dwarf

Question 58

Where are elements heavier than iron primarily produced?

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

Question 59

Observations from the Compton Gamma Ray Observatory showed that gamma-ray bursters were located throughout the sky. This told us that

A) the bursts were not produced among stars in the disk of our galaxy.
B) the bursts were not produced among stars in the nuclear bulge of our galaxy.
C) the bursts are not associated with planets in our solar system
D) the bursts were not produced in our Sun
E) All of the above

Question 60

The slowing of clocks in strongly curved space time is known as

A) gravitational radiation.
B) time dilation.
C) gravitational curvature.
D) gravitational red shift.
E) hyperspace drag.

Question 61

The search for black holes involves searching for

A) single stars that emit large amounts of X-rays.
B) X-ray binaries where the compact companion has a mass in excess of 3 .
C) large spherical regions from which no light is detected.
D) pulsars with periods less than one millisecond.
E) pulsars that are orbited by planets.

Question 62

As material flows into a black hole

A) the material will experience time dilation.
B) the material will become hotter.
C) the material will produce an absorption spectrum.
D) the material will appear to us to fall into the black hole very rapidly.
E) a and b

Question 63

Millisecond pulsars that are very old are

A) believed to be the result of mass transfer from a companion that increases the spin of the pulsar.
B) all single objects.
C) not spinning as rapidly they seem because they have four hot spots that produce the flashes.
D) X-ray binaries.
E) gamma-ray bursters.

Question 64

If the inner accretion disk around a black hole has a temperature of 10 6 K, at what wavelength will it radiate the most energy? Hint: wavelength in nm =3,000,000/T in K

A) 10⁶ nm
B) 3 nm
C) 3*10⁶ nm
D) 1 nm
E) 3*10¹¹ nm

Question 65

The singularity of a black hole

A) is found outside the event horizon.
B) is located within the event horizon.
C) can only be located if the black hole is in a binary system.
D) doesn t exist since all black holes have a finite size.

Question 66

The event horizon

A) is believed to be a singularity.
B) is a crystalline layer.
C) has a radius equal to the Schwarzschild radius.
D) marks the inner boundary of a planetary nebula.
E) is located at the point where synchrotron radiation is created around a pulsar.

Question 67

The Schwarzschild radius of a 1 black hole is approximately

A) 3 km.
B) 1,500,000 km, the size of the Sun
C) 150,000,000 km or 1 AU.
D) 3 10 13 km or 1 pc.

Question 68

The escape velocity of an object depends on
I. the mass of that object.
II. the mass of the object trying to escape.
III. the distance from the center of the object and the escaping object.
IV. the speed of light.

A) I, II, III, IV
B) I II
C) I,III
D) I, II, IV
E) I, III, IV

Question 69

The peculiar system SS 433
I. is emitting beams of energy and matter.
II. is producing a spectrum with both a red and a blue shift.
III. probably contains an accretion disk.
IV. is the result of a planetary nebula.

A) I
B) III
C) II III
D) I, II, III
E) I, II, III, IV

Question 70

Cygnus X-1 and LMC X-3 are black holes if the masses of the unseen companions are

A) less than 5 solar masses.
B) more than 5 solar masses.
C) between 0.4 and 1.4 solar masses.
D) less than 0.4 solar masses
E) not larger than the masses of the stars that we can see.

Question 71

The material that accretes onto a neutron star or black hole is expected to emit X-rays because

A) the material will produce synchrotron radiation.
B) hydrogen nuclei begin to fuse and emit high energy photons.
C) the material will become hot enough that it will radiate most strongly a X-ray wavelengths.
D) as the material slows down it converts thermal energy to gravitational potential energy.
E) none of the above

Question 72

Fraud in science is rare because it is difficult to commit. Why is it difficult to commit fraud in science?

A) Science requires that experimental and theoretical findings be reproducible.
B) All scientists are bound by a code of ethics preventing them from publishing fraudulent work.
C) Scientific results are reviewed by other scientists before they are published.
D) Scientific journals only allow certain highly trusted individuals to publish their work.
E) a and c above

Question 73

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

Question 74

A pulsar requires that a neutron star
I. rotate rapidly.
II. have a radius of at least 10 km.
III. have a strong magnetic field.
IV. rotate on an axis that is different from the axis of the magnetic field.

A) I,III
B) I, IV
C) II, III, IV
D) I, III, IV
E) I, II, III, IV

Question 75

The first pulsar was discovered by __________ in November of 1967.

A) Jocelyn Bell
B) Isaac Newton
C) Albert Einstein
D) Walter Baade
E) Edwin Hubble

Question 76

The orbit of the binary pulsar, PSR 1936+16, studied by Taylor and Hulse

A) is so small that the orbital period is smaller than the pulsar period.
B) is growing smaller, presumably by emitting gravitational waves.
C) provides evidence that it is being orbited by at least 6 planets the size of Jupiter.
D) shows large changes each time an X-ray burst is emitted from the system.
E) contains a white dwarf and a black hole.

Question 77

An isolated black hole in empty intergalactic space would be difficult to detect because

A) there would be no stars behind it whose light it could bend or lens gravitationally
B) it could not emit light from inside its event horizon
C) no companion stars would be affected by its gravitational field
D) no matter would be falling into it to create an x-ray emitting accretion disk
E) All of the above

Question 78

Why don t all supernova remnants contain pulsars?

A) All supernova remnants do contain pulsars.
B) Some supernova explosions form white dwarfs instead of the neutron stars necessary for pulsars.
C) Pulsars slow down and quite producing the pulses before the supernova remnant dissipates.
D) The pulsar may be tipped so that the beams do not sweep past Earth.
E) b and c above.

Question 79

None of the pulsars emit pulses of visible light because

A) pulsars are to hot to emit visible light.
B) pulsars contain black holes that won t let visible light escape.
C) the gravitational field of a pulsar is so great that the visible light emitted is red shifted.
D) pulsars are too far away for the visible light to be bright enough to be detected at Earth.
E) A few pulsars do emit visible light pulses.

Question 80

Which of the following objects is considered to possibly contain a black hole?

A) The central star of the Crab nebula
B) The Orion nebula.
C) LMC X-3
D) Algol
E) PSR 1257+12