Deck 11: Stellar Explosions

Question 1

A massive star can fuse only up to the element silicon in its core.

Answer 1

False

Question 2

The final core collapse of a massive star takes about 13 seconds.

Answer 2

False

Question 3

Because they all involve the detonation of a carbon-rich white dwarf at Chandrasekhar's limit, all type I supernovae are equally luminous.

Answer 3

True

Question 4

A carbon-detonation supernova starts out as a white dwarf in a close binary system.

Question 5

The density of a neutron star is comparable to the density of an atomic nucleus.

Question 6

The Crab Nebula and the Orion Nebula are regions where new stars are being formed.

Question 7

Novae are more closely related to type II than to type I supernovae.

Question 8

Except for hydrogen and most of the helium, all the elements have been formed through stellar nucleosynthesis.

Question 9

A Type I supernova involves the collapsing core of a high mass star.

Question 10

Novae always occur in a close binary star system.

Question 11

Type II supernovae have little hydrogen in their spectra; it had been used up already.

Question 12

Iron is the most stably bonded atomic nucleus.

Question 13

A recurring nova could eventually explode as a Type I supernova.

Question 14

Because they all involve formation of iron in cores of massive stars, all type II supernovae are equally luminous.

Question 15

Stellar nucleosynthesis is responsible for the existence of all elements except hydrogen.

Question 16

Once carbon is formed in massive star cores, the majority of nuclei formed form then on will belong to even numbered elements, due to addition to more helium nuclei as alpha particles.

Question 17

Newly formed neutron stars have weak magnetic fields which strengthen over time, due to the conservation of angular momentum.

Question 18

Iron nuclei are the most tightly bound nuclei, which is why their production leads to type II supernovae.

Question 19

It takes less and less time to fuse heavier and heavier elements inside a high mass star.

Question 20

Unlike supernovae, novae can explode more than once, increasing their luminosity by thousands of times.

Question 21

The element with the most stable nucleus and smallest mass per particle is

A) uranium.
B) argon.
C) helium.
D) hydrogen.
E) iron.

Question 22

Gamma-ray bursts seem to come primarily from neutron star binaries in the plane of our own Milky Way Galaxy.

Question 23

A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates what kind of object?

A) Hypernova
B) Nova
C) Gamma ray burstar
D) Type I supernova
E) Type II supernova

Question 24

All neutron stars are pulsars, but not all pulsars are neutron stars.

Question 25

As a star's evolution approaches the Type II supernova, we find

A) the heavier the element, the less time it takes to make it.
B) the heavier the element, the higher the temperature to fuse it.
C) helium to carbon fusion takes at least 100 million K to start.
D) photodisintegration of iron nuclei begins at 10 billion K to ignite the supernova.
E) All of the above are correct.

Question 26

Like most pulsars, the Crab Nebula neutron star is known only by its radio pulses.

Question 27

Astronomers believe that gamma-ray bursters emit radiation equally in all directions.

Question 28

Beyond the formation of iron, nuclear energy can be produced only by

A) fusion of still heavier elements.
B) ionization of the radioactive nuclei.
C) fission of heavy nuclei back toward lighter ones.
D) gravity.
E) the dark force.

Question 29

What would happen if mass is added to a 1.4 solar mass white dwarf?

A) The star would explode as a nova.
B) The star's radius would increase.
C) The star would immediately collapse into a black hole.
D) The star would erupt as a carbon detonation (type I) supernova.
E) The core would collapse as a type II supernova.

Question 30

An iron core cannot support a star because

A) iron is the heaviest element, and sinks upon differentiation.
B) iron has poor nuclear binding energy.
C) iron cannot fuse with other nuclei to produce energy.
D) iron supplies too much pressure.
E) iron is in the form of a gas, not a solid, in the center of a star.

Question 31

The supernova that formed M-1, the Crab Nebula, was observed in

A) 1572 AD by Tycho Brahe.
B) 1604 AD by Johannes Kepler.
C) 1054 AD by Chinese and Middle Eastern astronomers.
D) 1006 by observers in the southern hemisphere.
E) about 9,000 BC by all our ancestors.

Question 32

For a nova to occur, the system must have already been a

A) astrometric binary.
B) detached binary.
C) spectroscopic binary.
D) mass-transfer binary.
E) eclipsing binary.

Question 33

A 20 solar mass star will stay on the main sequence for 10 million years, yet its iron core can exist for only a

A) day.
B) week.
C) month.
D) year.
E) century.

Question 34

Besides direct formation of a black hole in a hypernova, some think that mergers between neutron stars can create even longer-lived gamma ray bursts as well.

Question 35

The remains of type II supernovae (massive star, core collapse supernovae) are seen in the sky as

A) nebulae that are shrinking as the central mass pulls them in.
B) nebulae that are expanding at thousands of kilometers per hour.
C) nebulae that are stellar nurseries.
D) white dwarfs.
E) white holes.

Question 36

The spectra of the youngest stars show the most heavy elements present.

Question 37

The core of a highly evolved high mass star is a little larger than

A) our solar system.
B) our Sun.
C) Jupiter.
D) Earth.
E) a white dwarf.

Question 38

Short duration gamma-ray bursts are explained as the merger of two neutron stars.

Question 39

A star can be a supernova

A) in predictable cycles of decades.
B) a few times, at unpredictable intervals.
C) only if it can fuse iron in its core.
D) before it reaches the main sequence, if it is massive enough.
E) only once.

Question 40

The Chandrasekhar mass limit is

A) 0.08 solar masses.
B) 0.4 solar masses.
C) 1.4 solar masses.
D) 3 solar masses.
E) 8 solar masses.

Question 41

The average density of neutron stars approaches

A) a million times that of normal matter.
B) a million times that of even a white dwarf.
C) about 10¹⁷ kg/m³, similar to the density of atomic nuclei.
D) about 10¹⁸ times that of water.
E) infinity.

Question 42

Neutron stars have

A) very strong bi-polar magnetic fields.
B) weak or non-existent magnetic fields.
C) periods of days or weeks.
D) monopolar fields that switch polarity every rotation.
E) no relation to pulsars.

Question 43

What direct evidence do astronomers have that supports the heavy element formation in stars?

A) The presence of technetium in giant star spectra
B) Observed elemental abundances
C) Gamma-ray emissions from decay of cobalt 56 in supernovae
D) Light curves of type-I supernovae
E) All of the above are evidence of this.

Question 44

The iron we commonly find in our surroundings came from

A) the iron core of a massive star which exploded as a type I supernova.
B) planetary nebulae.
C) jets ejected by a rapidly spinning pulsar.
D) material ejected by a nova explosion.
E) decay of nickel 56 and cobalt 56 in a supernova remnant.

Question 45

When helium capture occurs with a carbon 12 nucleus, what results?

A) Nitrogen 14
B) Oxygen 16
C) Neon 20
D) Silicon 28
E) Nickel 56

Question 46

Two important properties of young neutron stars are

A) extremely slow rotation and a strong magnetic field.
B) extremely rapid rotation and a weak magnetic field.
C) extremely rapid rotation and a strong magnetic field.
D) no rotation and a weak magnetic field.
E) no rotation and no magnetic field.

Question 47

In a neutron star, the core is

A) made of compressed neutrons in contact with each other.
B) electrons and protons packed so tightly they are in contact.
C) constantly expanding and contracting.
D) primarily iron and silicon.
E) no longer rotating.

Question 48

The vast majority of pulsars are known only from their pulses in

A) X-rays.
B) gamma-rays.
C) visible light.
D) microwaves.
E) radio waves.

Question 49

What is stellar nucleosynthesis?

A) The formation of heavier elements inside stars
B) The formation of planetary nebulae by red giants
C) The formation of stars from a nucleus of contracting material
D) The formation of white dwarfs, neutron stars, and black holes from stars
E) The process by which stars form interstellar dust

Question 50

Neutron stars and black holes are formed by

A) the star formation process.
B) mass transfer in binary star systems.
C) novae.
D) type I supernovae.
E) type II supernovae.

Question 51

The helium capture process tends to produce chiefly

A) only carbon.
B) stable elements.
C) even numbered elements.
D) odd numbered elements.
E) only radioactive elements.

Question 52

Which type of heavy atomic nuclei are most common, and why?

A) Transuranium elements, for only very heavy elements are made in supernovae.
B) Odd numbered elements, because hydrogen is the building block for all heavier elements.
C) Even numbered elements, for helium is "giant food" for everything beyond itself.
D) Metals, for iron is the last abundant element formed before the type II supernova.
E) Noble gases, for they are the most stable elements.

Question 53

Nearly all the elements found in nature were formed inside stars, EXCEPT for

A) carbon and silicon.
B) hydrogen and helium.
C) helium and carbon.
D) silver and technetium.
E) uranium and radium.

Question 54

Pulsars

A) spin very rapidly when they're young.
B) are the cause of gamma-ray bursts.
C) spin very slowly when they're young, and gradually spin faster as they age.
D) generally form from 25 solar mass stars.
E) emit radio in all directions.

Question 55

What is the reason a type-I supernova slows its dimming after about 2 months?

A) The planetary nebula cooled enough to form a dust shell.
B) Energy is released from the decay of radioactive cobalt 56 to iron 56.
C) The supernova remnant suddenly becomes transparent.
D) The burst of energy carried by neutrinos is finally observed.
E) Energy from the supernova's shock wave is released as it hits interstellar matter.

Question 56

An object more massive than the Sun, but roughly the size of a city, is a

A) supernova remnant.
B) white dwarf.
C) brown dwarf.
D) neutron star.
E) red dwarf.

Question 57

The making of abundant iron nuclei is typical of

A) planetary nebula ejection.
B) the helium flash.
C) all novae.
D) type I supernovae.
E) type II supernovae.

Question 58

Supernova remnants differ from star forming regions because, although there is ionized hydrogen in both, supernova remnants

A) don't look like star forming regions.
B) are much bigger than star forming regions.
C) are located far from star forming regions.
D) are more diffuse than star forming regions.
E) contain no ionizing stars.

Question 59

The heaviest nuclei of all are formed

A) in the horizontal branch.
B) in dense white dwarfs.
C) during nova explosions.
D) in the ejection of matter in the planetary nebula.
E) in the core collapse that set the stage of Type II supernovae.

Question 60

The heaviest nuclei of all are formed

A) by neutron capture during a type II supernova explosion.
B) during a nova explosion.
C) during a carbon detonation supernova.
D) during carbon burning in the giant stage.
E) during the triple alpha process.

Question 61

Relatively long duration gamma-ray bursts are produced by

A) novae.
B) supernovae.
C) hypernovae.
D) neutron star mergers.
E) black hole mergers.

Question 62

The maximum mass of a white dwarf is about ________ times the mass of the Sun.

Question 63

What makes the Crab pulsar somewhat unusual among pulsars in general?

A) It is the most intense source of X-rays in the sky.
B) It is the fastest pulsar known.
C) It is the oldest pulsar observed.
D) Its period is not regular like other pulsars.
E) It is rather bright at visible wavelengths.

Question 64

Whose work with SETI lead to the discovery of pulsars in 1967?

A) Jocelyn Bell
B) Sir Bernard Lovell
C) Anthony Hewish
D) Martin Schwarzschild
E) Stephen Hawking

Question 65

After reaching its peak luminosity in hours or days, a nova declines in brightness over a period of a few ________ before returning to its pre-explosion luminosity.

Question 66

The central star of the Crab Nebula has now collapsed into a ________, whose energy keeps this famous nebula visible even in binoculars.

Question 67

Which statement about young stars is FALSE?

A) They contain a larger fraction of heavy elements than previous generations.
B) They are born in a dustier environment than earlier generations.
C) They are more likely to have planets forming with them than earlier generations.
D) The high mass stars will be more likely to produce heavier elements as they evolve.
E) Being young, they will have more pure hydrogen than earlier generations.

Question 68

Type II supernovae and star forming regions are related to one another because

A) they both contain ionized hydrogen.
B) they both involve high mass ionizing stars.
C) the shock waves of a supernova can trigger star formation.
D) as a result of both processes, lighter elements are transformed into heavier elements.
E) all of the above.

Question 69

In the lighthouse model

A) the star literally turns on and off like a lighthouse beacon.
B) all pulsars must have their poles pointed directly toward us.
C) if the beam sweeps across us, we will detect a pulse of radiation.
D) the period of pulsation must speed up as the neutron star continues collapsing.
E) the period of pulsation slows down due to the drag of the remnant on its field.

Question 70

What compelling evidence links pulsars to neutron stars?

A) Both pulsars and neutron stars can be found in globular star clusters.
B) Pulsars are known to evolve into neutron stars.
C) Only a small, very dense source could rotate that rapidly without flying apart.
D) Pulsars are always found in binary systems with neutron stars.
E) Both pulsars and neutron stars have been discovered near the Sun.

Question 71

What makes the Crab Nebula supernova remnant unusual as a supernova remnant?

A) It is the biggest supernova remnant visible.
B) It is the remnant of a supernova that was observed in the 20th century.
C) It is the nearest supernova remnant.
D) It is the oldest supernova remnant known.
E) It is the remnant of a supernova observed by humans.

Question 72

In the lighthouse model

A) pulsars are observable only if they lie in the galactic plane.
B) pulsars are navigational devices created by interstellar navigators as discovered by Jocelyn Bell in 1967.
C) all pulsars have their poles pointed directly at us or they would be not observable.
D) if the beams sweeps across us, we can observe the pulse.
E) the period of pulsation must speed up as the neutron star continues contracting.

Question 73

Of all elements, ________ has the most stable and tightly bound nucleus.

Question 74

The supernova of 1054 AD produced

A) a remnant still visible to the naked eye, the Crab Nebula, M-1.
B) a pulsar with a period of 33 milliseconds, visible optically.
C) the closest known neutron star to our Sun.
D) the most famous black hole.
E) no remaining visible trace, as it was a type I supernova.

Question 75

In a nova, there is a white dwarf, an evolving companion star, and a(n) ________ surrounding the white dwarf's equator.

Question 76

An iron core will collapse in approximately one ________ in a type II supernova event.

Question 77

The radioactive decay of cobalt 56 into iron 56 affects the light curve of a type I supernova about ________ after the initial peak in luminosity.

Question 78

The Crab Nebula is a bright, long lasting supernova remnant that was made by a ________ supernova.

Question 79

A hypernova creates

A) a black hole.
B) a pulsar.
C) a neutron star.
D) short-duration gamma-ray bursts.
E) Both B and C are correct.

Question 80

Type I supernovae result from ________ stars which have accreted sufficient additional mass via mass transfer from a close binary companion.