Astronomy Chapter 6 Answers – Flashcards

Unlock all answers in this set

Unlock answers
question
that the carbon, oxygen, and many elements essential to life were created by nucleosynthesis in stellar cores
answer
What do astronomers mean when they say that we are all "star stuff"?
question
nuclear fusion and gravitational contraction
answer
Which two energy sources can help a star maintain its internal thermal pressure?
question
low-mass star
answer
What type of star our Sun?
question
between 8 and 100 solar masses
answer
What is the range of star masses for high-mass stars?
question
what surface temperature and luminosity it will have at each stage of its life
answer
What can we learn about a star from a life track on an H-R diagram?
question
Degeneracy pressure varies with the temperature of the star
answer
Which of the following statements about degeneracy pressure is not true?
question
conduction
answer
All of the following are involved in carrying energy outward from a star's core except
question
high-mass stars
answer
Which stars have convective cores?
question
both A and B
answer
Which of the following properties make flare stars so active?
question
Its core contracts, but its outer layers expand and the star becomes bigger and brighter
answer
When happens when a star exhausts its core hydrogen supply?
question
It is fusing hydrogen into helium in a shell outside the core
answer
What is happening inside a star while it expands into a subgiant?
question
MV
answer
Which of the following spectral types is more likely to be a flare star?
question
cooler and brighter
answer
Compared to the star it evolved from, a red giant is
question
100 million K
answer
At approximately what temperature can helium fusion occur?
question
Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward
answer
Why does a star grow larger after it exhausts its core hydrogen?
question
3
answer
How many helium nuclei fuse together when making carbon?
question
carbon
answer
The helium fusion process results in the productin of
question
the core quickly heats up and expands
answer
What happens after a helium flash?
question
a red giant star whose atmosphere becomes carbon-rich through convection from the core
answer
What is a carbon star?
question
the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star
answer
What is a planetary nebula?
question
It becomes a white dwarf
answer
What happens to the core of a star after a planetary nebula occurs?
question
protostar, main-sequence, red giant, white dwarf
answer
Which of the following sequences correctly describes the stages of life for a low-mass star?
question
hotter and dimmer
answer
Compared to the star it evolved from, a white dwarf is
question
the atmospheres of red giant stars
answer
Most interstellar dust grains are produced in
question
a type of hydrogen fusion that uses carbon, nitrogen, and oxygen atoms as catalysts
answer
What is the CNO cycle?
question
iron
answer
Which element has the lowest mass per nuclear particle and therefore cannot release energy by either fusion or fission?
question
the core contracts and becomes a black hole
answer
What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure?
question
stars that are at least several times the mass of the Sun
answer
What types of stars end their lives with supernovae?
question
Betelgeuse would remain a dot of light but would suddenly become so bright that, for a few weeks, we'd be able to see this dot in the daytime
answer
Which of the following statements about stages of nuclear burning in a massive star is not true?
question
the sudden collapse of an iron core into a compact ball of neutrons
answer
Which event marks the beginning of a supernova?
question
either a neutron star or a blackhole
answer
After a supernova event, what is left behind?
question
It was the nearest supernova detected in nearly 400 years
answer
Why is Supernova 1987A particularly important to astronomers?
question
The two stars should be the same age, so the more massive one should have become a giant first
answer
You discover a binary star system in which one member is 15M Sun main-sequence star and the other star is a 10M Sun giant. Why would you be surprised, at least at first?
question
The giant must once have been the more massive star but transferred some of its mass to its companion
answer
You discover a binary star system in which one member is a 15M Sun main-sequence star and the other star is a 10M Sun giant. How do we believe that a star system such as this might have come to exist?
question
Existence of heavy elements
answer
Why do scientists think that our solar system must have formed sometime after nearby supernovae explosions?
question
a very massive main-sequence star
answer
Degeneracy pressure is the source of the pressure that stops the crush of gravity in all the following except
question
they are both very hot and very small
answer
White dwarfs are so called because
question
a few tons
answer
A teaspoonful of white dwarf material on Earth would weigh
question
the sun
answer
Which of the following is closest in mass to a white dwarf?
question
The more massive the white dwarf, the greater the degeneracy pressure and the faster the speeds of its electrons. Near 1.4 solar masses, the speeds of the electrons approach the speed of light, so more mass cannot be added without breaking the degeneracy pressure
answer
Why is there an upper limit to the mass of a white dwarf?
question
It will cool down and become a cold black dwarf
answer
What is the ultimate fate of an isolated white dwarf?
question
The white dwarf undergoes a catastrophic collapse, leading to a type of supernova that is somewhat different from that which occurs in a massive star but is comparable in energy
answer
Suppose a white dwarf is gaining mass because of accretion in a binary system. What happens if the mass someday reaches the 1.4 solar-mass limit?
question
Our Sun will probably undergo at least one nova when it becomes a white dwarf about 5 billion years from now
answer
Which of the following statements about novae is not true?
question
electron degeneracy pressure
answer
What kind of pressure supports a white dwarf?
question
1.4 solar masses
answer
What is the upper limit to the mass of a white dwarf?
question
It has a smaller radius
answer
How does a 1.2 solar-mass white dwarf compare to a 1.0 solar-mass white dwarf?
question
Earth
answer
Which of the following is closest in size (radius) to a white dwarf?
question
a white dwarf star with a red giant binary companion
answer
What kind of star is most likely to become a white-dwarf supernova?
question
The spectrum of a massive-star supernova shows prominent hydrogen lines, white the spectrum of a white-dwarf supernova does not
answer
Observationally, how can we tell the difference between a white-dwarf supernova and a massive star supernova?
question
either a neutron star or a black hole
answer
After a massive-star supernova, what is left behind?
question
There is an upper limit less than 3 solar masses, but we do not yet know precisely what it is
answer
What is the upper limit to the mass of a neutron star?
question
more than Mt. Everest
answer
A teaspoonful of neutron star material on Earth would weigh
question
a city
answer
Which of the following is closest in size (radius) to a neutron star?
question
The entire mass of Earth would end up as a thin layer, about 1 cm thick, over the surface of the neutron star
answer
Which of the following best describes what would happen if a 1.5 solar-mass neutron star, with a diameter of a few kilometers, were suddenly to appear in your hometown?
question
An object that emits flashes of light several times per second or more, with near perfect regularity
answer
From an observational standpoint, what is a pulsar?
question
a rapidly rotating neutron star
answer
From a theoretical standpoint, what is a pulsar?
question
As the star spins, beams of radio radiation sweep through space. If one of the beams crosses Earth, we observe a pulse
answer
What causes the radio of a pulsar?
question
No massive object, other than a neutron star, could spin as fast as we observe pulsars spin
answer
How do we know that the pulsars are neutron stars?
question
It will slow down, the magnetic field will weaken, and it will become invisible
answer
What is the ultimate fate of an isolated pulsar?
question
any object from which the escape velocity exceeds the speed of light
answer
What is the basic definition of a black hole?
question
Light coming from a compact massive object, such as a neutron star, will be redshifted
answer
How does the gravity of an object affect light?
question
During a supernova, if a star is massive enough for its gravity to overcome neutron degeneracy of the core, the core will be compressed until it becomes a black hole
answer
How does a blackhole form from a massive star?
question
If the sun magically disappeared and was replaced by a blackhole of the same mass, Earth would soon be sucked into the black hole
answer
Which of the following statements about black holes is not true?
question
several examples of flattened accretion disks being "fed" by a large companion star can be seen clearly in photos from the Hubble Space Telescope
answer
In some cases, a supernova in a binary system may lead to the eventual formation of an accretion disk around the remains of the star that exploded. All of the following statements about such accretion disks are true except:
question
sudden, intense X-ray bursts
answer
When we see X rays from an accretion disk in a binary system, we can't immediately tell whether the accretion disk surrounds a neutron star or a black hole. suppose we then observe each of the following phenomena in this system. which one would force us to immediately rule out the possibility of a black hole?
question
300 million km
answer
What is the Schwarzschild radius of a 100 million-solar-mass black hole?
question
neutron star
answer
A 10 solar mass main sequence will produce which of the following remnants?
question
It is the center of the black hole, a place of infinite density where the known laws of physics cannot describe the conditions
answer
What do we mean by the singularity of a black hole?
question
We don't know for sure: we only know what to expect based on the predictions of general relativity
answer
How do we know what happens at the event horizon of a black hole?
question
Observations from the Compton Gamma-Ray Observatory show that gamma-ray bursts come randomly from all directions in the sky
answer
Prior to the 1990s, most astronomers assumed that gamma-ray bursts came from neutron stars with accretion disks. How do we now know that this hypothesis was wrong?
question
because the current evidence suggests that they are the most powerful bursts of energy that ever occur anywhere in the universe, but we don't know how they are produced
answer
Why do astronomers consider gamma-ray bursts to be one of the greatest mysteries in astronomy?
Get an explanation on any task
Get unstuck with the help of our AI assistant in seconds
New