Astronomy Chapter 23

Which of the following statements about the life of a star with a mass like the Sun is correct?

as the star is dying, a considerable part of its mass will be lost into space

A star with a mass like the Sun which will soon die is observed to be surrounded by a large amount of dust and gas -- all material it has expelled in the late stages of its life. If astronomers want to observe the radiation from such a giant star surrounded by its own debris, which of the following bands of the spectrum would be the best to use to observe it?

infrared

When a single star with a mass equal to the Sun dies, it will become a

white dwarf

Which of the following stages will the Sun definitely go through as it gets older?

source of a planetary nebula

black dwarf

red giant

white dwarf

Which of the following is a characteristic of degenerate matter in a white dwarf star?

the electrons get as close to each other as possible and resist further compression

A white dwarf, compared to a main sequence star with the same mass, would always be:

smaller in diameter

The astrophysicist who first calculated the highest mass that a dying star can have and still be a white dwarf was

S. Chandrasekhar

A charming friend of yours who has been reading a little bit about astronomy accompanies you to the campus observatory and asks to see the kind of star that our Sun will ultimately become, long, long after it has turned into a white dwarf. Why is the astronomer on duty going to have a bit of a problem satisfying her request?

after a white dwarf cools off it becomes too cold and dark to emit visible light

Astronomers observe a young cluster of stars, where stars with three times the mass of the Sun are still on the main sequence of the H-R diagram. Yet the cluster contains two white dwarfs, each with a mass less than 1.4 times the mass of the Sun. If we can show that the white dwarfs are definitely part of the cluster, how can their presence so soon in the life of the cluster be explained?

some stars can lose a lot of mass on their way to becoming white dwarfs; thus the white dwarfs could have started out as quite massive stars

Because white dwarfs are small, as their name implies, they are hard to see. What is a way astronomers have to find white dwarfs that distinguishes them from main sequence stars?

because white dwarfs get really hot, we can search for their ultraviolet radiation

The most stable (tightly bound) atomic nucleus in the universe is:

iron

When the mass of a star's core is greater than 1.4 times the mass of the Sun, degenerate electrons can't keep it stable as a white dwarf. Instead it becomes:

a neutron star

In a collapsing star of high mass, when electrons and protons are squeezed together with enormous force, they turn into a neutron and a:

neutrino

A neutron star is as dense as

the nucleus of an atom

Which of the following is the smallest?

neutron star

Which of the following is the largest (in diameter)?

red giant

After the core of a massive star becomes a neutron star, the rest of the star's material

explodes outward as a supernova

Astronomers have long realized that supernovae -- when the explode -- give off an enormous amount of light, but observations of Supernova 1987A ( in the Large Magellanic Cloud) revealed that the supernova gives off even more energy in another form? That form is:

neutrinos

If observations of supernovae in other galaxies show that such an explosion happens in a Spiral galaxy like the Milky Way on average every 25 to 100 years, why have astronomers on Earth not seen a supernova explosion in our Galaxy since 1604?

the disk of our Galaxy contains a great deal of dust, which tends to block the light of supernova explosions from more distant parts of our Galaxy

Which of the following is NOT a result of supernova explosions?

neutron star is disrupted and tears apart into many pieces

Your sweetheart gives you a piece of gold jewelry as a present to celebrate you passing your astronomy class. Where did the gold atoms in that gift originally come from (where were they most likely made)?

they were built up from smaller nuclei during a supernova explosion

Astronomers believe that the many supernova explosions that happened in the Milky Way Galaxy could have played a role in the evolution of life over billions of years. How would they have influenced the development of life on Earth?

the cosmic rays produced by supernova explosions would have contributed to the rate of mutations over many generations

Elements heavier than iron can be created during

a supernova explosion

Which of the following statements about a Type II Supernova is true?

A Type II supernova occurs at the end of the life of a star 10 times the mass of our Sun or more

Which of the following statements about Supernova 1987A is FALSE?

it exploded relatively close to us, in a spiral arm of the Milky Way Galaxy

Which of the following statements about Supernova 1987A is TRUE?

- It was observed with instruments in space as well as on the ground

- It was only visible from the Southern Hemisphere of the Earth

- Neutrinos from the explosion were actually detected on Earth

- Astronomers believe it was the explosion of a star that was originally a massive type O

In a supernova like SN1987A, once the crisis of iron fusion has begun, roughly how long does it take the star's core to collapse?

a few tenths of a second

How did Supernova 1987A demonstrate that new elements are made in supernova explosions?

the light output was kept at high levels by the energy released from radioactive elements that decay very quicky; these must have been made by the supernova

Some of the energy produced in the event we call Supernova 1987A was used to blow the star apart. Out of the following places that the energy of this event could go, which absorbed by far the most energy?

the production of huge numbers of neutrinos

What kind of telescope did Jocelyn Bell use to discover pulsars in 1968?

radio

When neutron stars were first predicted theoretically, no scientist expected to be able to detect one of them across interstellar distances. What enabled astronomers to find neutron stars in the late 1960's?

we found strongly magnetic neutron stars whose whirling beams of energy were detected as pulsars

Which of the following statements about the Crab Nebula is FALSE?

inside, there are a number of newly formed massive stars (O and B type stars)

Which of the following statements about the Crab Nebula is TRUE?

- the nebula still puts out more energy (at all wavelengths) than 100,000 Suns

- we can detect. a pulsar inside the nebula using both radio waves and visible light

- the neutron star inside shows clear evidence of slowing down just a little bit in its rotation

- it is the remnant of a supernova explosion first seen on Earth in 1054 AD

Astronomers have noticed that the visible filaments in the Crab Nebula are moving toward us at great speed. How can they know about motions like this?

from the Doppler shift in the line radiation from the nebula

Astronomers have concluded that pulsars are

rotating neutron stars

In the model that astronomers have developed for pulsars, why fo they suggest that there must be two beams of energy coming from the pulsar?

because neutron star beams come out of the north and south poles of a magnetic field

Which of the following is one reason we do not detect a pulsar in many remnants of supernova explosions?

the pulsar beam doesn't happen to point toward is in many cases

Where does the energy come from that allows the Crab Nebula to keep shining almost 1000 years after the star exploded?

a neutron star is slowing down (losing rotation energy)

A member of the college football team wants to weigh as much as possible. Assuming he could somehow survive on all of them, at the surface of which object would he weigh the most?

a neutron star

Although centuries ago, astronomers thought that a nova was a new star, appearing for the first time in the heavens, today we know that it is:

a binary star system in which one star is a white dwarf and mass is being transferred to it

When a star undergoes a nova explosion, it may return to its "quiet state" and later become a nova again. What would allow a nova explosion to happen to a star more than once

the star that goes nova has a companion star near it, which dumps material onto the first star and continues to do so even after the first nova explosion

In a Type Ia supernova, the cause of the violent outburst is:

the transfer of so much mass from a companion star that a white dwarf goes "over the limit" and collapses, causing an enormous amount of sudden fusion

A type Ia supernova involves the transfer of mass from one star to a companion white dwarf? Yet, in some cases, astronomers cannot locate a star near where they see Type Ia explosions. How do they explain the absence of a companion star>

they suggest that some type Ia supernova are caused by the collision of two white dwarfs, both of which then explode

Astronomers have discovered pulsars spinning 500 x per second or more. How do astronomers think pulsars got to be spinning so outrageously fast?

Such fast-spinning pulsars have companion stars near them, which dump material on the pulsar and that spins it faster and faster

Which of the following statements about the life of a star with a mass like the Sun is correct?

a. before the star dies, it will fuse dozens of elements in its core

b. as the star is dying, a considerable part of its mass will be lost into space

c. after the main sequence stage, there is no further fusion of hydrogen anywhere in the star

d. at the end of its life, the star will explode as a supernova

e. the core of this star will be too massive to form a white dwarf

as the star is dying, a considerable part of its mass will be lost into space

When the mass of a star's core is greater than 1.4 times the mass of the Sun, degenerate electrons can't keep it stable as a white dwarf. Instead, it becomes:

a neutron star

What incident in a massive star's life sets off (begins) the very quick chain of events that leads to a supernova explosion?

the fusion of iron

Which of the following is the smallest?

a. white dwarf

b. neutron star

c. red giant

d. main sequence star

e. protostar

neutron star

Which of the following is the largest (in diameter)?

a. neutron star

b. white dwarf

c. red giant

d. main sequence star

e. the cloud of fossil-fuel pollution around Bayonne, New Jersey

red giant

Which of the following stages can only occur in the life of a low-mass star (whose final mass is less than 1.4 times the mass of the Sun)?

a. proto-star

b. main-sequence

c. red giant

d. white dwarf

e. supernova

white dwarf

Astronomers have long realized that supernovae -- when they explode -- give off an enormous amount of light. But observations of Supernova 1987A (in the Large Magellanic Cloud) revealed that the supernova gives off even more energy in another form? That form is:

neutrinos

If observations of supernovae in other galaxies show that such an explosion happens in a spiral galaxy like the Milky Way on average every 25 to 100 years, why have astronomers on Earth not seen a supernova explosion in our Galaxy since 1604?

. the disk of our Galaxy contains a great deal of dust, which tends to block the light of supernova explosions from more distant parts of our Galaxy

Which of the following is NOT a result of supernova explosions?

a. many of the elements the star fused during its life are blasted out into space

b. new heavier elements (including such heavy nuclei lead and uranium) are fused by neutron bombardment during the explosion

c. a tremendous flood of high-energy cosmic ray particles is released

d. any planets within a few dozen LY of the explosion are bathed with life-threatening radiation

e. the neutron star is disrupted and tears apart into many pieces

the neutron star is disrupted and tears apart into many pieces

Your sweetheart gives you a piece of gold jewelry as a present to celebrate your passing your astronomy class. Where did the gold atoms in that gift originally come from (where were they most likely made)?

they were built up from smaller nuclei during a supernova explosion

Elements heavier than iron can be created during:

a. the big bang

a supernova explosion

Which of the following statements about a Type II Supernova is true?

a. Type II supernovas happen when a white dwarf is overloaded with mass from a companion star

b. Type II supernovas occur in the Milky Way Galaxy just about every year. It's rare to have a year without one happening in the Galaxy.

c. A Type II supernova is so faint that we miss most of the ones that happen in our Galaxy

d. A Type II supernova occurs at the end of the life of a star with 10 times the mass of our Sun or more

e. A Type II supernova is a less powerful explosion than any other type; it can't make any of the elements heavier than iron

A Type II supernova occurs at the end of the life of a star with 10 times the mass of our Sun or more

Which of the following statements about Supernova 1987A is FALSE?

a. it exploded relatively close to us, in a spiral arm of the Milky Way Galaxy

b. it was only visible from the Southern Hemisphere of the Earth

c. astronomers believe it was the explosion of a star that was originally a massive type O

d. neutrinos from the explosion were actually detected on Earth

e. it was observed with instruments in space as well as on the ground

it exploded relatively close to us, in a spiral arm of the Milky Way Galaxy

In a supernova like SN1987A, once the crisis of iron fusion has begun, roughly how long does it take the star's core to collapse?

a few tenths of a second

. What kind of telescope did Jocelyn Bell use to discover pulsars in 1968?

radio

Which of the following statements about the Crab Nebula is FALSE?

a. it is the remnant of a supernova explosion first seen on Earth in 1054 AD

b. the nebula still puts out more energy (at all wavelengths) than 100,000 Suns

c. inside, there are a number of newly formed massive stars (O and B type stars)

d. the neutron star inside shows clear evidence of slowing down just a little bit in its rotation

e. we can detect a pulsar inside the nebula using both radio waves and visible light

inside, there are a number of newly formed massive stars (O and B type stars)

Astronomers have noticed that the visible filaments in the Crab Nebula are moving toward us at great speed. How can they know about motions like this?

a. from the width of the pulsar pulses

b. from the color of the nebula's continuous radiation

c. from the spacing of the pulsar pulses

d. from the H-R diagram

e. from the Doppler shift in the line radiation from the nebula

from the Doppler shift in the line radiation from the nebula

Astronomer have concluded that pulsars are

a. rotating black holes

rotating neutron stars

In the model that astronomers have developed for pulsars, why do they suggest that there must be two beams of energy coming from the pulsar?

because neutron star beams come out of the north and south poles of a magnetic field

Which of the following is one reason we do not detect a pulsar in many remnants of supernova explosions?

a. most stars (our own Sun, for example) don't rotate at all, so no pulsar can form

b. the radiation with which we detect pulsars doesn't get through the Earth's atmosphere

c. the pulsar beam doesn't happen to point toward us in many cases

d. many supernova remnants contain white dwarfs or black dwarfs

e. the little green men inside put shades on their pulsars for privacy

the pulsar beam doesn't happen to point toward us in many cases

Where does the energy come from that allows the Crab Nebula to keep shining almost a 1000 years after the star exploded? (Who ultimately "pays the energy bill"?)

a neutron star is slowing down (losing rotation energy)

When a star undergoes a nova explosion, it may return to its "quiet state" and later become a nova again. What would allow a nova explosion to happen to a star more than once?

the star that goes nova has a companion star near it, which dumps material onto the first star and continues to do so even after the first nova explosion

A type Ia supernova involves the transfer of mass from one star to a companion white dwarf? Yet, in some cases, astronomers cannot locate a star near where they see Type Ia explosions. How do they explain the absence of a companion star?

they suggest that some type Ia supernova are caused by the collision of two white dwarfs, both of which then explode

How did observations with the Compton Gamma-ray Observatory show that gamma-ray bursts were not coming from the Milky Way Galaxy?

the gamma-rays came from all over the sky, not just the plane of the Galaxy

When the BeppoSAX satellite, together with telescopes on the ground, helped astronomers pinpoint the location of the first gamma-ray burst to be identified with something that gave off visible light, the burst's location turned out to be in

in a distant galaxy

A rich donor to your college gets fascinated by gamma-ray bursts, and wants to give money to find out more about what produces them. Which of the following should her money go to fund?

a network of visible-light telescopes which can automatically swing to a location provided by an alert system at NASA

Which of the following statements about our best candidate for long-duration gamma-ray bursts is FALSE?

a. it involves the merger of two black holes

b. most of the bursts it causes can be shown to be in distant galaxies

c. the bursts it produces are more frequently seen and are brighter and easier to pinpoint

d. the mechanism involves a special type of supernova explosion

e. a rotating, magnetic star corpse most likely produces jets (or beams)

it involves the merger of two black holes

Astronomers now have a good idea for explaining how the short-duration gamma-ray bursts might come about. Which of the following is part of their explanation?

these bursts most likely come from the merger of two neutron stars