Deck 12: Stellar Evolution

Question 1

Brown dwarfs are ____.

A) stars with a very thick dust sphere around them, so they appear "brown"
B) low mass M type stars with hundreds of planets
C) an anomaly because they are extremely small but have relatively high temperature
D) protostars that could not ignite the fusion of hydrogen at their core
E) has a surface temperature of 2500 K by fusing hydrogen

Answer 1

D

Question 2

Globular clusters have approximately how many stars?

A) 100,000 - 1,000,000
B) 10,000 - 90,000
C) 5,000 - 10,000
D) 1000 - 5000
E) less than 1000

Answer 2

A

Question 3

Astronomers can determine the interiors of main sequence stars by _____.

A) studying their atmospheres
B) creating stellar models
C) detailed observations of the Sun
D) using the Hertzsprung-Russell Stellar Model (HRSM)
E) satellite observations of the closest stars

Answer 3

B

Question 4

Giant and supergiant stars are rare because they do not form as often as main sequence stars.

Question 5

As a star like the Sun exhausts hydrogen in its core, the outer layers of the star become hotter and more luminous.

Question 6

To determine the structure of the interior of a star, astronomers must balance density, luminosity, and ____.

A) mass
B) temperature
C) mass and temperature
D) mass and opacity
E) temperature and opacity

Question 7

As a one-solar-mass star evolves off the main sequence, it will probably undergo a _____.

A) nova burnout
B) helium flash
C) hydrogen flash
D) helium bang
E) carbon flash

Question 8

The age of a star cluster can be approximated by finding its turnoff point in the distribution of data points that represent stars on the H-R Diagram.

Question 9

Astronomers determine the internal structure of a star by using stellar models, since they cannot "see" into the interior of a star.

Question 10

The helium flash stage will always completely destroy a star and any planets nearby it

Question 11

There is a mass-luminosity relationship because stars support their weight by generating energy, and more massive stars have more weight to support.

Question 12

The energy emitted from the surface of a main sequence star is less than the energy generated in the core.

Question 13

When the Sun moves off the main sequence, it will initially become a red supergiant.

Question 14

Observing star clusters will give astronomers needed data for stellar evolution because all the stars in the cluster have the same ____.

A) masses
B) temperatures
C) ages
D) luminosities
E) apparent magnitudes

Question 15

All the elements heavier than helium on the periodic table, including the ones in your body, were created in the cores of massive stars.

Question 16

Degenerate matter has two peculiar properties that can affect a star.  One is that the degenerate gas resists compression, and the other is that the degenerate gas ____.

A) is not density dependent
B) does depend on temperature
C) does not depend on temperature
D) is not pressure dependent.
E) does depend on the type of nuclei present

Question 17

Observing star clusters will give astronomers needed data for stellar evolution because all the stars are the same age.

Question 18

Stellar models can easily be accomplished by using a simple hand calculator.

Question 19

What is the upper limit of a brown dwarf's size?

A) no upper limit
B) 0.50 solar masses
C) 0.10 solar masses
D) 0.08 solar masses
E) less than 0.08 solar masses

Question 20

The fusion of helium into carbon will take a temperature of at least

A) 5 million degrees Kelvin
B) 10 million degrees Kelvin
C) 50 million degrees Kelvin
D) 100 million degrees Kelvin
E) 600 million degrees Kelvin

Question 22

Figure: Main-Sequence Stars
What is the approximate age of the star cluster in the accompanying figure?

A) 10 million years
B) 100 million years
C) 10 billion years
D) 100 billion years
E) Cannot be determine from the given data.

Question 23

Where are the Cepheid and RR Lyrae variable stars located on the H-R Diagram?

A) just above and to the right of B type stars
B) just above and to the right of O type stars
C) in the variable strip
D) in the instability strip
E) outside the H-R Diagram as missing items

Question 24

Why is the Cepheid's period related to their luminosity?

Question 25

A open star cluster will have a(n) _____________ turn-off point than an older star cluster.

Question 26

When a gas is so dense that most of its electrons are not free to change their energies, it is called _______________.

Question 27

The lower limit for a main sequence star is _______________ solar masses.

Question 28

Why do Cepheids pulsate?

Question 29

The period-luminosity relation for Cepheid and RR Lyrae variable stars can be used for ______________.

Question 30

Match the following list of events or labels to the location on the figure.  The figure represents the post-main-sequence phase of a large mass star (upper curve) and a low mass star (lower curve).  Use one letter for each question.  "A", "B", and "C" are the axes of the diagram.
 _____ giants

A) A
B) B
C) C
D) D
E) E
F) F
G) G
H) H
I) I
J) J
K) K

Question 31

Why are massive stars more luminous than low mass stars? That is, why is there a mass-luminosity relation?

Question 32

Cepheid variable stars are classified as either ____.

A) Type A or Type B
B) Type I or Type II
C) Class A or Class B
D) Class I or Class II
E) Type C or Type R

Question 33

Why is there a lower end in the main sequence of the H-R diagram?

Question 34

Explain how the age of a star cluster provides evidence of stellar evolution.

Question 35

Because of the period-luminosity relation for Cepheids and RR Lyrae variable stars, astronomers are able to _____

A) determine the relationship between the period of pulses and luminosity
B) measure the mass of a star
C) calculate a star's diameter
D) determine the chemical composition of a Type I Cepheid
E) narrow their study to eclipsing binary stars only

Question 36

Explain how one of the four laws of stellar structure works.

Question 37

If you observe a variable star with a period of 50 days as a yellow, supergiant star, then you most likely have seen a(n) ____.

A) degenerate star
B) RR Lyrae variable star
C) eclipsing binary star
D) Cepheid variable star
E) Type I Pulsar

Question 38

A(n) _______________star is any star that changes its brightness significantly and repeatedly.

Question 39

Cepheid and RR Lyrae variable stars change their brightness by ____.

A) atmospheric explosions of hydrogen gas
B) internal changes in their fusion processes
C) a combination of atmospheric explosions and internal changes
D) a combination of atmospheric explosions and physically pulsating
E) changing its period between pulses

Question 40

The Instability Strip on the H-R Diagram is the location for what type of stars _______________.

Question 41

Stars support their weight by generating ____.

A) magnetic fields throughout the star
B) magnetic fields throughout the star
C) energy in their centers
D) magnetic-plasmas at their core
E) energy-plasmas at their core

Question 42

List the four laws of stellar structure.

Question 43

What is degenerate matter?

Question 44

List the two basic types of intrinsic variable stars.

Question 45

Why is there an upper end in the main sequence of the H-R diagram?

Question 46

Helium fusion is sometimes referred to as the _______________  because three helium nuclei are needed to make a carbon nucleus, and because the helium nucleus is called an alpha particle.

Question 47

The two elements a one-solar-mass star uses over the course of its entire evolution are   _______________ and _____________.

Question 48

Cepheid variables can be used to determine distances because their _____________ can be determined from their _____________.

Question 49

Define nuclear fusion.

Question 50

Variables of a certain type are called Cepheid variables because the first one discovered was in the _____________ Cepheus.

Question 51

As a main sequence star evolves off the main sequence, the helium core is contracting while the outer envelope is _______________.

Question 52

Briefly explain why there is a main sequence on the H-R Diagram.