Stars & Galaxies - Test 2
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2.
Which of the following describes a velocity (as opposed to a speed)?
15 newtons
20 kilometers per hour, headed north
9.8 meters per second squared (m/s2)
5 light-years
300,000 kilometers per second
20 km/hr, headed north
3.
The acceleration of gravity on Earth is approximately 10 m/s2 (more precisely, 9.8 m/s2). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds?
20 m/s
30 m/s
30 m/s2
10 m/s2
10 m/s
30 m/s
4.
Which of the following examples describes a situation where a car is experiencing a net force?
The car is moving at constant speed in a straight line.
The car is stopped on a hill.
The car is holding constant speed around a curve.
The car is holding constant speed down a straight hill because the driver is applying the brakes.
The car is holding constant speed around a curve.
5.
Suppose you lived on the Moon. Which of the following would be true?
Both your weight and your mass would be the same as they are on Earth.
Your weight would be less than your weight on Earth, but your mass would be the same as it is on Earth.
Both your weight and your mass would be less than they are on Earth.
Your mass would be less than your mass on Earth, but your weight would be the same as it is on Earth.
Your weight would be less than your weight on Earth, but your mass would be the same as it is on Earth.
6.
In which of the following cases would you feel weightless?
while parachuting from an airplane
while falling from a roof
while walking on the Moon
while accelerating downward in an elevator
while falling from a roof
7.
In outer space, astronauts are weightless because:
Read this to me
They are in free-fall.
The spacecraft provides counteracting forces.
The gravity is very weak.
There is no gravity.
They are in free-fall.
8.
Which of the following statements is not one of Newton’s Laws of Motion?
In the absence of a net force acting on it, an object moves with constant velocity.
The rate of change of momentum (momentum = mass x velocity) of an object is equal to the net force applied to the object.
For any force, there always is an equal and opposite reaction force.
What goes up must come down.
What goes up must come down.
9.
Newton’s Second Law of Motion tells us that the net force applied to an object equals its __________.
momentum multiplied by velocity
mass multiplied by velocity
mass multiplied by acceleration
mass multiplied by energy
mass multiplied by acceleration
10.
According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them __________.
decreases by a factor of 9
increases by a factor of 9
decreases by a factor of 3
increases by a factor of 3
decreases by a factor of 9
11.
According to modern science, approximately how old is the Sun?
400 million years
10,000 years
25 million years
4.5 billion years
4.5 billion years
12.
The Sun will exhaust its nuclear fuel in about __________.
5 million years
5 billion years
50 billion years
5000 AD
5 billion years
13.
The source of energy that keeps the Sun shining today is __________.
gravitational contraction
nuclear fission
nuclear fusion
chemical reactions
nuclear fusion
14.
When we say that the Sun is a ball of plasma, we mean that __________.
Read this to me
the Sun is made of material that acts like a liquid acts on Earth
the Sun consists of gas in which many or most of the atoms are ionized (missing electrons)
the Sun is roughly the same color as blood
the Sun is made of atoms and molecules
the Sun consists of gas in which many or most of the atoms are ionized (missing electrons)
15.
What is the Sun’s approximate composition (by mass)?
70% hydrogen, 28% helium, 2% other elements
100% hydrogen and helium
50% hydrogen, 25% helium, 25% other elements
90% dark matter, 10% ordinary matter
70% hydrogen, 28% helium, 2% other elements
16.
From the center outward, which of the following lists the “layers” of the Sun in the correct order?
core, corona, radiation zone, convection zone, photosphere, chromosphere
core, convection zone, radiation zone, corona, chromosphere, photosphere
core, radiation zone, convection zone, photosphere, chromosphere, corona
core, radiation zone, convection zone, corona, chromosphere, photosphere
core, radiation zone, convection zone, photosphere, chromosphere, corona
17.
The outer atmosphere of the Sun is called
the corona
the parallax
the penumbral
the photosphere
the convection
the corona
18.
What are the appropriate units for the Sun’s luminosity?
joules
newtons
kilograms
watts
watts
19.
The Sun’s visible surface (that is, the surface we can see with our eyes) is called the __________.
photosphere
core
chromosphere
corona
photosphere
20.
The Sun’s average surface (photosphere) temperature is about _____.
1,000 K
1,000,000 K
5,800 K
37,000 K
5,800 K
21.
The proton–proton chain is __________.
the linkage of numerous protons into long chains
the specific set of nuclear reactions through which the Sun fuses hydrogen into helium
another name for the force that holds protons together in atomic nuclei
an alternative way of generating energy that is different from the fusion of hydrogen into helium
the specific set of nuclear reactions through which the Sun fuses hydrogen into helium
22.
To estimate the central temperature of the Sun, scientists __________.
use computer models to predict interior conditions
monitor changes in Earth’s atmosphere
use hot gas to create a small Sun in a laboratory
send probes to measure the temperature
use computer models to predict interior conditions
23.
Which of the following is not a characteristic of the 11-year sunspot cycle?
Read this to me
The Sun’s entire magnetic field flip-flops with each cycle, so that the overall magnetic cycle averages 22 years.
The number of sunspots on the Sun at any one time gradually rises and falls, with an average of 11 years between the times when sunspots are most numerous.
The likelihood of seeing solar prominences or solar flares is higher when sunspots are more common and lower when they are less common.
The sunspot cycle is steady, so that each 11-year cycle is nearly identical to every other 11-year cycle.
The sunspot cycle is steady, so that each 11-year cycle is nearly identical to every other 11-year cycle.
24.
How is the sunspot cycle directly relevant to us here on Earth?
The Sun’s magnetic field, which plays a major role in the sunspot cycle, affects compass needles that we use on Earth.
Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.
The sunspot cycle strongly influences Earth’s weather.
The brightening and darkening of the Sun that occurs during the sunspot cycle affects plant photosynthesis here on Earth.
The sunspot cycle is the cause of recent global warming.
Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.
25.
What is a common trigger for solar flares?
Chemical reactions
Sudden increase in sunlight
Strong winds on the Sun's surface
Magnetic field lines snapping
Magnetic field lines snapping
Sunspots are NOT...
connected by a loop of magnetic field lines.
regions of strong magnetic field that tend to occur in pairs.
more numerous every 11-year cycle.
concentrated near the Sun's equator as the activity in a cycle peaks.
cooler regions than their surroundings.
concentrated near the Sun's equator as the activity in a cycle peaks.
27.
What prevents the Sun from collapsing under the force of gravity?
the Sun is too solid to collapse.
fusion creates the necessary energy, which in its turn generates the necessary outward gas pressure to balance the force of gravity.
the radiative zone is strong enough to keep the surface and the core separated.
the sunspots on the surface rotate, appear and disappear in order to keep the Sun balanced.
the gravitational pull from all the planets keeps the Sun from collapsing.
fusion creates the necessary energy, which in its turn generates the necessary outward gas pressure to balance the force of gravity.
28.
Most solar energy leaves the core of the Sun in the form of
sound waves.
rising hot gas.
protons and electrons.
hydrogen atoms.
photons.
photons.
29.
Granulation or the mottled appearance of the whole surface of the Sun is an indication of what physical process at work in the Sun?
the outflow of neutrinos from the interior.
magnetic hydrogenics.
rapid rotation of the Sun.
thermonuclear fusion of hydrogen in the Sun's surface layers.
convective motion of gases in the upper portion of the Sun's interior.
convective motion of gases in the upper portion of the Sun's interior.
30.
Which of the following is true about fusion?
The material out of which Earth-like planets are formed does not result from fusion.
Fusion becomes a process called fission at conditions of low temperature.
The most important set of thermonuclear fusion reactions in the Sun is called the proton-proton chain, where four hydrogen nuclei will ultimately produce one helium nucleus.
Fusion is the way by which elements lighter than hydrogen are built.
Fusion describes the way in which radioactive material decays.
The most important set of thermonuclear fusion reactions in the Sun is called the proton-proton chain, where four hydrogen nuclei will ultimately produce one helium nucleus.
2.
Stellar parallax is
the apparent change in the distances to a star if its light is dimmed by passing through interstellar clouds.
the apparent backward motion of the outer planets as the Earth overtakes them in their orbit.
the circular or elliptical motion of a star in a binary system, as the two stars orbit around each other.
the difference between the apparent brightness and absolute brightness of a star.
the apparent shift that we see in the position of a nearby star as we orbit around the Sun.
the apparent shift that we see in the position of a nearby star as we orbit around the Sun.
3.
What is the approximate chemical composition (by mass) with which all stars are born?
95% hydrogen, 4% helium, no more than 1% heavier elements
98% hydrogen, 2% helium
half hydrogen and half helium
3/4 hydrogen, 1/4 helium, no more than about 2% heavier elements
3/4 hydrogen, 1/4 helium, no more than about 2% heavier elements
4.
The total amount of power (in watts, for example) that a star radiates into space is called its __________.
flux
apparent brightness
absolute magnitude
luminosity
luminosity
5.
According to the inverse square law of light, how will the apparent brightness of an object change if its distance to us triples?
Read this to me
Its apparent brightness will decrease by a factor of 9.
Its apparent brightness will increase by a factor of 3.
Its apparent brightness will decrease by a factor of 3.
Its apparent brightness will increase by a factor of 9.
Its apparent brightness will decrease by a factor of 9.
6.
Assuming that we can measure the apparent brightness of a star, what does the inverse square law for light allow us to do?
Read this to me
Calculate the star’s surface temperature if we know either its luminosity or its distance.
Determine the distance to the star from its apparent brightness.
Determine both the star’s distance and luminosity from its apparent brightness.
Calculate the star’s luminosity if we know its distance, or calculate its distance if we know its luminosity.
Calculate the star’s luminosity if we know its distance, or calculate its distance if we know its luminosity.
7.
Star A has an apparent magnitude = 3 and star B has an apparent magnitude = 5. Which star is brighter in our sky?
Star B
The two stars have the same brightness in our sky, but Star A is closer to us than Star B.
There is not enough information to answer the question.
Star A
Star A
8.
The spectral sequence sorts stars according to
luminosity.
radius.
core temperature.
surface brightness.
mass.
surface brightness.
9.
From hottest to coolest, the order of the spectral types of stars is __________.
Read this to me
ABCDEFG
OMKGFBA
OBAGFKM
ABFGKMO
OBAFGKM
OBAFGKM
10.
Our Sun is a star of spectral type _____.
G
S
M
F
G
11.
Astronomers can measure a star’s mass in only certain cases. Which one of the following cases might allow astronomers to measure a star’s mass?
Read this to me
The star is of spectral type A.
We know the star’s luminosity and distance.
The star is of spectral type G.
The star is a member of a binary star system.
The star is a member of a binary star system.
12.
Which of the following terms is given to a pair of stars that we can determine are orbiting each other only by measuring their periodic Doppler shifts?
Read this to me
double star
spectroscopic binary
eclipsing binary
visual binary
spectroscopic binary
13.
The axes on a Hertzsprung-Russell (H-R) diagram represent __________.
Read this to me
luminosity and surface temperature
mass and luminosity
mass and radius
luminosity and apparent brightness
luminosity and surface temperature
14.
What can we infer, at least roughly, from a star’s luminosity class?
its age in years
its size (radius)
its mass
its surface temperature
its size (radius)
15.
On an H-R diagram, stellar radii __________.
are impossible to determine
are greatest in the lower left and least in the upper right
increase diagonally from the lower left to the upper right
decrease from left to right
increase diagonally from the lower left to the upper right
16.
On an H-R diagram, stellar masses __________.
Read this to me
are greatest in the lower left and least in the upper right
decrease from upper left to lower right
are impossible to determine
can be determined for main sequence stars but not for other types of stars
can be determined for main sequence stars but not for other types of stars
17.
High-mass stars have __________ lifetimes than low-mass stars.
Read this to me
much longer
slightly longer
much shorter
slightly shorter
much shorter
18.
On an H-R diagram, a red supergiant would be located in the __________.
upper left
lower left
lower right
upper right
upper right
19.
What is the common trait of all main-sequence stars?
They are all spectral type G.
They generate energy through hydrogen fusion in their core.
They are in the final stage of their lives.
They all have approximately the same mass.
They generate energy through hydrogen fusion in their core.
20.
Study this H-R diagram. Which of the following stars is the most massive? (The red arrows help you locate these stars on the diagram.)
DX Cancri
Beta Centauri
Bellatrix
Vega
Beta Centauri
21.
Study this H-R diagram. Which of the following stars is the largest in size (radius)? (The red arrows help you locate these stars on the diagram.)
Aldebaran
Alpha Centauri B
Antares
Canopus
Antares
22.
Study this H-R diagram. Which of the following stars has (or had) the longest hydrogen fusing lifetime? (The red arrows help you locate these stars on the diagram.)
Barnard’s star
the Sun
Alpha Centauri B
Betelgeuse
Barnard’s star
23.
On the main sequence, stars obtain their energy
by converting helium to carbon, nitrogen, and oxygen.
by converting hydrogen to helium.
from chemical reactions
from nuclear fission.
from gravitational contraction.
by converting hydrogen to helium.
24.
What type of binary star is it when one star passes in front of another?
Visual binary
Eclipsing binary
Passing binary
Hidden binary
Eclipsing binary
25.
Which of the following terms is given to a pair of stars that we can determine are orbiting each other only by measuring their periodic Doppler shifts?
spectroscopic binary
none of the above
eclipsing binary
visual binary
double star
spectroscopic binary
2.
Which of the following statements comparing open and globular star clusters is true?
Globular clusters typically contain a few hundred stars, while open clusters typically contain tens to hundreds of thousands of stars.
Open clusters are found both in the disk and the halo of the galaxy, while globular clusters are found only in the halo.
Open clusters contain only main-sequence stars, while globular clusters contain only giants.
Stars in open clusters are relatively young, while stars in globular clusters are very old.
Stars in open clusters are relatively young, while stars in globular clusters are very old.
3.
What do we mean by the main-sequence turnoff point of a star cluster, and what does it tell us?
Read this to me
It is the mass of the most massive star in the star cluster, and it tells us the cluster’s size.
It is the luminosity class of the largest star in a star cluster, and it tells us the cluster’s age.
It is the point in a star cluster beyond which main sequence stars are not found, and it tells us the cluster’s distance.
It is the spectral type of the hottest main sequence star in a star cluster, and it tells us the cluster’s age.
???
4.
What do we mean by the interstellar medium?
Read this to me
the name of an oracle who can channel messages from beings that live near the star called Vega
the dust that fills the halo of the Milky Way galaxy
the gas and dust that lies in between the stars in the Milky Way galaxy
the middle section of the Milky Way galaxy
the gas and dust that lies in between the stars in the Milky Way galaxy
5.
The interstellar clouds called molecular clouds are __________.
the cool clouds in which stars form
the clouds in which elements such as carbon, nitrogen, and oxygen are made
the clouds that are made mostly of complex molecules such as carbon dioxide and sulfur dioxide
the hot clouds of gas expelled by dying stars
the cool clouds in which stars form
6.
Which of the following types of molecule is the most abundant in an interstellar molecular cloud?
Read this to me
H2O
H2
CO
NH3
H2
7.
Interstellar dust consists mostly of __________.
the same tiny particles found in household dust
microscopic particles of carbon and silicon
tiny grains of water ice
ozone “smog”
hydrogen and helium atoms
microscopic particles of carbon and silicon
8.
Which part of the electromagnetic spectrum generally gives us our best views of stars forming in dusty clouds?
infrared
visible light
ultraviolet
blue light
infrared
9.
Suppose you look at a star that can be seen through the edge of a dusty interstellar cloud. The star will look __________ than it would if it were outside the cloud.
more redshifted
dimmer and bluer
brighter and redder
dimmer and redder
dimmer and redder
10.
Most interstellar clouds remain stable in size because the force of gravity is opposed by __________ within the cloud.
thermal pressure
radiation pressure
stellar winds
degeneracy pressure
thermal pressure
11.
What kind of gas cloud is most likely to give birth to stars?
a hot, low-density gas cloud
a hot, dense gas cloud
a cold, dense gas cloud
a cold, low-density gas cloud
a cold, dense gas cloud
12.
How are magnetic fields thought to affect star formation in molecular clouds?
There are no magnetic fields in interstellar space, so there is no effect.
They can help resist gravity, so that more total mass is needed before the cloud can collapse to form stars.
They accelerate the star formation process.
They allow small stars to form in isolation within gas clouds.
They can help resist gravity, so that more total mass is needed before the cloud can collapse to form stars.
13.
Which of the following statements about the first stars that were born in the universe is expected to be true?
They were made from pure energy.
They were made only from hydrogen and helium.
They were made approximately of 98% hydrogen and helium and 2% of heavier elements.
They were probably orbited only by terrestrial planets but no jovian planets.
They were made only from hydrogen and helium.
14.
What is a protostar?
a star in its final stage of life
a star that has planets
a star that is still in the process of forming
an intermediate-mass star
a star that is still in the process of forming
15.
When does a protostar become a main-sequence star?
when a piece of a molecular cloud first begins to contract into a star
when it becomes luminous enough to emit thermal radiation
at the instant that the first hydrogen fusion reactions occur in the protostar’s core
when the rate of hydrogen fusion becomes high enough to balance the rate at which the star radiates energy into space
when the rate of hydrogen fusion becomes high enough to balance the rate at which the star radiates energy into space
16.
Approximately what core temperature is required before hydrogen fusion can begin in a star?
10 trillion K
10 billion K
10 million K
10,000 K
1 billion K
10 million K
17.
The vast majority of stars in a newly formed star cluster are __________.
very high-mass, type O and B stars
about the same mass as our Sun
red giants
less massive than the Sun
less massive than the Sun
18.
Which of the following statements about brown dwarfs is not true?
Brown dwarfs are supported against gravity by degeneracy pressure, which does not depend on the object’s temperature.
All brown dwarfs have masses less than about 8% that of our Sun.
Brown dwarfs form like ordinary stars but are too small to sustain nuclear fusion in their cores.
Brown dwarfs eventually collapse to become white dwarfs.
Brown dwarfs eventually collapse to become white dwarfs.
19.
Cluster ages can be determined from
spectroscopic binaries.
main sequence fitting.
visual binaries.
pulsating variable stars.
main sequence turnoff.
main sequence turnoff.
20.
Which of the following luminosity classes refers to stars on the main sequence?
II
V
IV
I
III
V
21.
Why doesn't a brown dwarf become a star?
It does not have enough heavy elements to start fusion reactions.
It does not have enough mass for its core to get hot enough to start fusion reactions before
degeneracy pressure prevents further collapse.
Its luminosity is not high enough to qualify as an official star.
It always has a companion star that is hotter, and therefore, the brown dwarf is more like a planet than a star.
It does not have enough mass for its core to get hot enough to start fusion reactions before
22.
What happens to the rotation of a molecular cloud as it collapses to form a star?
The rotation increases the speed of collapse and produces more massive stars.
The rotation rate increases and results in a disk of material around a protostar.
The rotation rate remains the same and results in stellar rotation.
The rotation dissipates and any residual is left in small overall rotation of the star.
The rotation rate increases and results in a disk of material around a protostar.
23.
When discussing stellar lives, astronomers divide stars by mass into low-mass, intermediate-mass, and high-mass stars. Which category includes our Sun?
The Sun is a high-mass star.
The Sun is a low-mass star.
The Sun is an intermediate-mass star.
The Sun is a low-mass star.
2.
Which of the following stars will live longest?
3 solar-mass star
2 solar-mass star
4 solar-mass star
1 solar-mass star
1 solar-mass star
3.In the context of understanding stellar lives, “high-mass” stars have masses __________.
more than about 3 times the mass of our Sun
more than about 8 times the mass of our Sun
the same as our Sun
more than about 100 times the mass of our Sun
more than about 8 times the mass of our Sun
4.Which of the following lists the stages of life for a low-mass star in the correct order?
main-sequence star, white dwarf, red giant, planetary nebula, protostar
protostar, main-sequence star, red giant, supernova, neutron star
protostar, main-sequence star, red giant, planetary nebula, white dwarf
protostar, main-sequence star, planetary nebula, red giant
protostar, main-sequence star, red giant, planetary nebula, white dwarf
5.What happens when a main-sequence star exhausts its core hydrogen fuel supply?
The star becomes a neutron star.
The core shrinks while the rest of the star expands.
The core immediately begins to fuse its helium into carbon.
The entire star shrinks in size.
The core shrinks while the rest of the star expands.
6.The primary source of energy for a star as it grows in size to become a red giant is __________.
helium fusion in the central core
gravitational contraction
hydrogen fusion in the central core
hydrogen fusion in a shell surrounding the central core
hydrogen fusion in a shell surrounding the central core
7.
The overall helium fusion reaction is __________.
two helium nuclei fusing to form one beryllium nucleus
two hydrogen nuclei fusing to form one helium nucleus
three helium nuclei fusing to form one carbon nucleus
four helium nuclei fusing to form one oxygen nucleus
three helium nuclei fusing to form one carbon nucleus
8.What is a helium flash?
It is a sudden brightening of a low-mass star, detectable from Earth by observing spectral lines of helium.
It is the sudden onset of helium fusion in the core of a low-mass star.
It is a sudden brightening of a low-mass star, detectable from Earth by observing spectral lines of helium.
It is the ignition of helium shell fusion in a high-mass star with a carbon core.
It is the sudden onset of helium fusion in the core of a low-mass star.
9.An H-R diagram for a globular cluster will show a horizontal branch, which is a line of stars above the main-sequence but to the left of the subgiants and red giants. Which of the following statements about these horizontal branch stars is true?
Their sole source of energy is hydrogen shell fusion.
In a particular star cluster, all horizontal branch stars have the same spectral type.
They have inert (no fusion reactions) carbon cores.
They generate energy through both hydrogen fusion and helium fusion.
They generate energy through both hydrogen fusion and helium fusion.
10.
What is a planetary nebula?
gas ejected from a low-mass star in the final stage of its life
gas created from the remains of planets that once orbited a dead star
interstellar gas from which planets are likely to form in the not-too-distant future
the remains of a high-mass star that has exploded
gas ejected from a low-mass star in the final stage of its life
11.The ultimate fate of our Sun is to __________.
become a rapidly spinning neutron star
explode in a supernova
become a black hole
become a white dwarf that will slowly cool with time
become a white dwarf that will slowly cool with time
12.
Assume the following stars all have the same mass as our Sun. Which one does not have fusion occurring in its central core?
a main-sequence star
a main-sequence star in a binary star system
a helium core-fusion star
a red giant
a red giant
13.How are low-mass red giant stars important to our existence?
These stars provide most of the light that reaches us from globular clusters.
These stars manufactured most of the carbon atoms in our bodies.
These stars manufactured virtually all the elements out of which we and our planet are made.
These stars generate the energy that makes life on Earth possible.
These stars manufactured most of the carbon atoms in our bodies.
14.
Which of the following pairs of atomic nuclei would feel the strongest repulsive electromagnetic force if you tried to push them together?
hydrogen and hydrogen
helium and helium
hydrogen and deuterium
hydrogen and helium
helium and helium
15.
Which of the following stars will end its life in a supernova?
a 10 solar-mass star
the Sun
a 1 solar-mass red giant star
a neutron star
a 10 solar-mass star
16.
What is the CNO cycle?
The process by which helium is fused into carbon, nitrogen, and oxygen
The process by which carbon is fused into nitrogen and oxygen
The set of fusion reactions that have produced all the carbon, nitrogen, and oxygen in the universe
A set of steps by which four hydrogen nuclei fuse into one helium nucleus
A set of steps by which four hydrogen nuclei fuse into one helium nucleus
17.To predict whether a star will eventually fuse oxygen into a heavier element, what do you need to know about the star?
its overall abundance of elements heavier than helium
its luminosity
its mass
how much oxygen it now has in its core
its mass
Why is iron significant to understanding how a supernova occurs?
The fusion of iron into uranium is the reaction that drives a supernova explosion.
Iron cannot release energy either by fission or fusion.
Supernovae often leave behind neutron stars, which are made mostly of iron.
Iron is the heaviest of all atomic nuclei, and thus no heavier elements can be made.
Iron cannot release energy either by fission or fusion.
19.
After a supernova explosion, the remains of the stellar core can be __________.
a white dwarf, neutron star, or black hole
a neutron star only
a black hole only
either a neutron star or a black hole
either a neutron star or a black hole
20.Why was is Supernova 1987A particularly important to astronomers?
It was the first supernova detected in nearly 400 years.
It provided the first evidence that supernovae really occur.
It occurred only a few light-years from Earth.
It was is the nearest supernova to have occurred at a time when we were capable of studying it carefully with telescopes.
It was is the nearest supernova to have occurred at a time when we were capable of studying it carefully with telescopes.
21.
Algol consist of a 3.7 MSun main-sequence star and a 0.8 MSun subgiant. Why does this seem surprising, at least at first?
It doesn’t make sense to find a subgiant in a binary star system.
A star with a mass of 3.7 MSun is too big to be a main-sequence star.
The two stars in a binary system should both be at the same stage of life; that is, they should either both be main-sequence stars or both be subgiants.
The two stars should be the same age, so we’d expect the subgiant to be more massive than the main-sequence star.
The two stars should be the same age, so we’d expect the subgiant to be more massive than the main-sequence star.
22.Which of the following statements about stages of nuclear burning (i.e., first-stage hydrogen burning, second-stage helium burning, etc.) in a massive star is NOT true?
Each successive stage lasts for approximately the same amount of time.
Each successive stage of fusion requires higher temperatures than the previous stages.
As each stage ends, the core shrinks further.
Each successive stage creates an element with a higher atomic weight.
Each successive stage lasts for approximately the same amount of time.
23.
What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure?
The star explodes violently, leaving nothing behind.
The core contracts and becomes a white dwarf.
The core contracts and becomes a ball of neutrons.
Gravity is not able to overcome neutron degeneracy pressure.
The core contracts and becomes a black hole.
The core contracts and becomes a black hole.