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Chapter 8

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Astronomy
Ryan Tram
Quiz by Ryan Tram, updated more than 1 year ago
Ryan Tram
Created by Ryan Tram about 8 years ago
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Question 1

Question
As a star exhausts the hydrogen in its core, what happens?
Answer
  • It becomes hotter and more luminous
  • It becomes hotter and less luminous
  • It becomes cooler and less luminous
  • It becomes cooler and more luminous

Question 2

Question
When does a star experience helium fusion?
Answer
  • just before it enters the main sequence
  • after it has become a red giant star
  • when it is on the horizontal branch
  • before it leaves the main sequence

Question 3

Question
Why are giant and supergiant stars rare?
Answer
  • The giant and supergiant stages are very short
  • The star blows up before the giant or supergiant stage is reached
  • They do not form as often as main sequence stars
  • The giant or supergiant stage is very long

Question 4

Question
Which of the following statements best describes why stars eventually die?
Answer
  • Their lifespan is limited
  • They exhaust all their fuel
  • Their cores become hotter
  • They become less luminous

Question 5

Question
Which of the following occurs during the giant stage?
Answer
  • helium fusion in the core and hydrogen fusion in the surrounding shell
  • hydrogen fusion in the core and helium fusion in the surrounding shell
  • hydrogen and helium fusion in the core
  • hydrogen flash

Question 6

Question
In what way are giants and supergiants similar?
Answer
  • They are the main sequence stars
  • They undergo a helium flash stage as they enter the main sequence
  • They are very luminous
  • Their cores expand rapidly to reach giant sizes

Question 7

Question
What is the term for a collection of 105 to 106 old stars in a region 30 to 100 light-years in diameter?
Answer
  • Herbig-Haro object
  • globular cluster
  • open cluster
  • giant cluster

Question 8

Question
What is the defining characteristic of stars within a cluster that are at the turnoff point?
Answer
  • They are just leaving the main sequence
  • They are just becoming white dwarfs
  • They are just entering the main sequence
  • They are about to explode in supernovae

Question 9

Question
What is the approximate age of the star cluster in the H-R diagram? (Hint: Main sequence stars of spectral types O and B have a core supply of hydrogen that is sufficient to last about 250 million years; types A and F, about 2 billion years; type G about 10 billion years; types K and M about 30 billion years. The apparent magnitude scale means that larger numbers are toward the bottom of the vertical axis.)
Image:
82842184-ab40-496f-8c4f-df47d36edc32 (image/png)
Answer
  • 200 million years
  • 2 billion years
  • 10 billion years
  • 30 billion years

Question 10

Question
Refer to the H-R diagram. What type of star do the two data points above spectral type “A” represent?
Image:
89fe7b48-a5d7-4300-b1ea-39f37a31f5f8 (image/png)
Answer
  • massive main sequence stars
  • massive supergiant stars
  • white dwarfs with mass less than the sun’s mass
  • white dwarfs with mass greater than twice the sun’s mass

Question 11

Question
Refer to the H-R diagram. What type of star do the data points above spectral type “M” represent?
Image:
73497c5b-55c6-462b-8ee2-1f6216c98a82 (image/png)
Answer
  • massive main sequence stars
  • massive main sequence stars with mass less than the sun’s mass
  • main sequence stars with luminosities higher than the sun’s luminosity
  • pre-main sequence stars

Question 12

Question
Refer to the H-R diagram. How would the H-R diagram of an older star cluster look different
Image:
894f091a-2600-4162-9731-632aaa1c09a4 (image/png)
Answer
  • The points would shift to the right, because all of the stars would have lower temperatures
  • The lower main sequence would look the same, but the turnoff would be at spectral type K or M
  • The points would shift down, because all of the stars would have lower luminosities
  • The lower main sequence would look the same, but the turnoff would be at spectral type F or A

Question 13

Question
Refer to the H-R diagram. How would the H-R diagram of a more distant star cluster look different?
Image:
f02c745f-f18e-4fa3-af49-fabc61a1fa4e (image/png)
Answer
  • The points would shift down, because all of the stars would have larger apparent magnitudes
  • The points would shift to the right, because all of the stars would appear to be cooler
  • The points would shift up, because all of the stars would have smaller apparent magnitudes
  • The points would shift to the left, because all of the stars would appear to be hotter

Question 14

Question
Which nuclear fuels does a one solar mass star use over the course of its entire lifespan?
Answer
  • hydrogen
  • hydrogen and helium
  • hydrogen, helium, and carbon
  • hydrogen, helium, carbon, and oxygen

Question 15

Question
Star A is a 1 solar mass white dwarf, and star B is a 1.3 solar mass white dwarf. How would they differ?
Answer
  • Star A has a smaller radius
  • Star B has a smaller radius
  • Star B is supported by neutron degeneracy pressure
  • Star A is hotter

Question 16

Question
What is the source of the energy radiated by a white dwarf?
Answer
  • the proton-proton chain
  • the CNO cycle
  • gravitational contraction after becoming a white dwarf
  • gravitational contraction during the white dwarf formation phase

Question 17

Question
What does the Chandrasekhar-Landau limit tell us?
Answer
  • Accretion disks can grow hot through friction
  • Neutron stars of more than 3 solar masses are not stable
  • White dwarfs more massive than 1.4 solar masses are not stable
  • Stars with a mass less than 0.5 solar masses will not go through helium flash

Question 18

Question
What is the ultimate fate of our Sun?
Answer
  • It will become a neutron star
  • It will explode in a supernova
  • It will become a white dwarf
  • It will explode in a nova

Question 19

Question
Which scenario is most likely to happen when the Sun enters the red giant stage?
Answer
  • Mercury, Venus, and Earth will be destroyed by the expanding Sun
  • Mercury will be destroyed by the expanding Sun, but Venus and Earth will remain intact
  • The Sun will engulf and destroy all planets in the Solar System
  • The Sun will never expand far enough to reach Mercury or any other planets in the Soar System

Question 20

Question
If the stars at the turnoff point of a cluster have a mass of 3 times the mass of the Sun, what is the age of the cluster?
Answer
  • 6.4×10^8 years
  • 3.3×10^9 years
  • 3.0×10^10 years
  • 1.6×10^11 years

Question 21

Question
Which of the following correctly describes a relationship between pressure, temperature, and density in degenerate matter?
Answer
  • Pressure depends only on the temperature
  • Pressure does not depend on temperature
  • Temperature depends only on density
  • Pressure does not depend on density

Question 22

Question
What is a white dwarf composed of?
Answer
  • hydrogen nuclei and degenerate electrons
  • helium nuclei and normal electrons
  • carbon and oxygen nuclei and degenerate electrons
  • degenerate iron nuclei

Question 23

Question
As a white dwarf cools, its radius remains the same. Why is this?
Answer
  • because pressure due to nuclear reactions in a shell just below the surface keeps it from collapsing
  • because pressure does not depend on temperature for a white dwarf, since the electrons are degenerate
  • because pressure does not depend on temperature, since the star has exhausted all its nuclear fuels
  • because material accreting onto it from a companion maintains a constant radius

Question 24

Question
What are the two longest stages in the life of a one solar mass star?
Answer
  • protostar, pre–main sequence
  • protostar, white dwarf
  • protostar, main sequence
  • main sequence, white dwarf

Question 25

Question
Which of the following is the most important factor that determines a life cycle of a star (for example, why some stars have a short life span)?
Answer
  • mass
  • temperature
  • luminosity
  • radius

Question 26

Question
What principle explains why matter flowing from one star in a binary system to its companion forms an accretion disk?
Answer
  • conservation of tidal forces
  • conservation of temperature
  • conservation of angular momentum
  • conservation of energy

Question 27

Question
Suppose you discover a binary star system with a 0.7 solar mass giant star and a 2 solar mass main sequence star. Why is this surprising?
Answer
  • 0.7 solar mass stars are not expected to become giants
  • All 2 solar mass stars should have left the main sequence
  • Giant stars are expected to destroy their companions, so the 2 solar mass star shouldn’t exist
  • The 2 solar mass star should have become a giant before the 0.7 solar mass star

Question 28

Question
When material expanding away from a star in a binary system reaches the edge of its Roche lobe, what happens?
Answer
  • The material will start to fall back toward the star
  • All of the material will accrete on to the companion
  • The material will no longer be gravitationally bound to the star
  • The material will increase in temperature and eventually undergo thermonuclear fusion

Question 29

Question
When mass is transferred toward a white dwarf in a binary system, the material forms a rapidly growing whirlpool of material. What is that whirlpool called?
Answer
  • an accretion disk
  • an Algol paradox
  • a planetary nebula
  • a supernova remnant

Question 30

Question
Under what conditions are Type Ia supernovae believed to occur?
Answer
  • when the core of a massive star collapses
  • when a white dwarf exceeds the Chandrasekhar-Landau limit
  • when hydrogen detonation occurs
  • when neutrinos in a massive star form a shock wave that explodes the star
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