Question 1

Roughly what percentage of stars in our galaxy are main-sequence stars?

Accepted Answer

A)  10 percent 
B)  25 percent 
C)  50 percent 
D)  75 percent 
E)  90 percent 
A)  10 percent 
B)  25 percent 
C)  50 percent 
D)  75 percent 
E)  90 percent

Question 2

A star's mass is the only characteristic that determines its position in the H-R diagram.

Accepted Answer

A) True 
 B)False

Question 3

A star's mass determines where it lies on the main sequence of an H-R diagram.

Accepted Answer

A) True 
 B)False

Question 4

If star A has a temperature that is twice as hot as the Sun but has the same luminosity as the Sun, the diameter of star A must be _________ times the diameter of the Sun.

Accepted Answer

A)  16 
B)  4 
C)  2 
D)  1/2 
E)  1/4 
A)  16 
B)  4 
C)  2 
D)  1/2 
E)  1/4

Question 5

In which region of an H-R diagram would you find the main-sequence stars with the widest habitable zones?

Accepted Answer

A)  upper left 
B)  upper right 
C)  center 
D)  lower left 
E)  lower right 
A)  upper left 
B)  upper right 
C)  center 
D)  lower left 
E)  lower right

Question 6

The habitable zone for the Sun covers the area that is between _________ from the Sun.

Accepted Answer

A)  0 to 0.8 AU 
B)  0.5 to 10 AU 
C)  1.2 to 4.2 AU 
D)  0.9 to 1.4 AU 
E)  0.2 to 10.2 AU 
A)  0 to 0.8 AU 
B)  0.5 to 10 AU 
C)  1.2 to 4.2 AU 
D)  0.9 to 1.4 AU 
E)  0.2 to 10.2 AU

Question 7

Why do O- and B-type stars have weaker hydrogen absorption lines than A-type stars?

Accepted Answer

A)  O- and B-type stars are cooler than A-type stars. 
B)  O- and B-type stars are smaller than A-type stars. 
C)  A larger fraction of hydrogen atoms in O- and B-type stars is ionized. 
D)  O- and B-type stars have converted much more of their hydrogen into heavier elements. 
E)  A-type stars have a higher mass than O- and B-type stars, so they have more hydrogen. 
A)  O- and B-type stars are cooler than A-type stars. 
B)  O- and B-type stars are smaller than A-type stars. 
C)  A larger fraction of hydrogen atoms in O- and B-type stars is ionized. 
D)  O- and B-type stars have converted much more of their hydrogen into heavier elements. 
E)  A-type stars have a higher mass than O- and B-type stars, so they have more hydrogen.

Question 8

Two stars with similar temperatures but different sizes will have:

Accepted Answer

A)  similar spectral types but different luminosities 
B)  similar luminosities but different brightnesses 
C)  similar brightnesses but different distances 
D)  similar distances but different masses 
E)  similar masses but different spectral types 
A)  similar spectral types but different luminosities 
B)  similar luminosities but different brightnesses 
C)  similar brightnesses but different distances 
D)  similar distances but different masses 
E)  similar masses but different spectral types

Question 9

The bright star named Rigel has a luminosity of 66,000 L $\wedge$  and a temperature of 11,000 K. What is its radius? Note that the temperature of the Sun is 5,800 K.

Accepted Answer

A)  5 R $\odot$ 
B)  30 R $\odot$ 
C)  70 R $\odot$ 
D)  135 R $\odot$ 
E)  190 R $\odot$ 
A)  5 R $\odot$ 
B)  30 R $\odot$ 
C)  70 R $\odot$ 
D)  135 R $\odot$ 
E)  190 R $\odot$

Question 10

Star A is a red star. Star B is a blue star. You are able to determine that both stars are the same size. Which star is more luminous?

Accepted Answer

A)  Star A is more luminous. 
B)  Star B is more luminous. 
C)  They have the same luminosities. 
D)  We also need to know the distance of the stars to determine their luminosity. 
E)  We cannot tell because color is not related to luminosity. 
A)  Star A is more luminous. 
B)  Star B is more luminous. 
C)  They have the same luminosities. 
D)  We also need to know the distance of the stars to determine their luminosity. 
E)  We cannot tell because color is not related to luminosity.

Question 11

Parallax is used to measure a star's:

Accepted Answer

A)  distance 
B)  velocity 
C)  luminosity 
D)  mass 
E)  radius 
A)  distance 
B)  velocity 
C)  luminosity 
D)  mass 
E)  radius

Question 12

Figure 1
-Figure 1 shows an H-R diagram, with five stars labeled A through E. Which star has the largest luminosity?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  E 
A)  A 
B)  B 
C)  C 
D)  D 
E)  E

Question 13

Explain how astronomers can use the blue and visual filters to determine the temperatures of stars.

Accepted Answer

Astronomers compare the relati

Question 14

What is the spectral type of stars that have the strongest hydrogen absorption lines? Why do stars that are hotter than these have weaker hydrogen lines?

Accepted Answer

A-type stars have the strongest hydrogen

Question 15

How is the unit of length known as a parsec defined?

Accepted Answer

The parsec is defined such tha

Question 16

Along the main sequence, how do the luminosity, temperature, radius, and mass of stars change as you go from the upper-left to the lower-right corners of the H-R diagram?

Accepted Answer

Stars near the upper-left end

Question 17

A parsec is a unit of time.

Accepted Answer

A) True 
 B)False

Question 18

Stars are made mostly of:

Accepted Answer

A)  helium 
B)  oxygen 
C)  hydrogen 
D)  nitrogen 
E)  carbon 
A)  helium 
B)  oxygen 
C)  hydrogen 
D)  nitrogen 
E)  carbon

Question 19

Eclipsing binary systems:

Accepted Answer

A)  orbit in the plane of the sky 
B)  exhibit large radial velocity shifts 
C)  contain equal mass stars 
D)  contain stars that pass in front of one another during their orbit 
E)  contain stars that can be resolved as two separate stars 
A)  orbit in the plane of the sky 
B)  exhibit large radial velocity shifts 
C)  contain equal mass stars 
D)  contain stars that pass in front of one another during their orbit 
E)  contain stars that can be resolved as two separate stars

Question 20

What is the approximate luminosity of a 5 M $\odot$  main-sequence star?

Accepted Answer

A)  50 L $\odot$ 
B)  80 L $\odot$ 
C)  150 L $\odot$ 
D)  280 L $\odot$ 
E)  510 L $\odot$ 
A)  50 L $\odot$ 
B)  80 L $\odot$ 
C)  150 L $\odot$ 
D)  280 L $\odot$ 
E)  510 L $\odot$

Exam 13: Taking the Measure of Stars

Roughly what percentage of stars in our galaxy are main-sequence stars?

A star's mass is the only characteristic that determines its position in the H-R diagram.

A star's mass determines where it lies on the main sequence of an H-R diagram.

If star A has a temperature that is twice as hot as the Sun but has the same luminosity as the Sun, the diameter of star A must be _________ times the diameter of the Sun.

In which region of an H-R diagram would you find the main-sequence stars with the widest habitable zones?

The habitable zone for the Sun covers the area that is between _________ from the Sun.

Why do O- and B-type stars have weaker hydrogen absorption lines than A-type stars?

Two stars with similar temperatures but different sizes will have:

The bright star named Rigel has a luminosity of 66,000 L ∧\wedge∧ and a temperature of 11,000 K. What is its radius? Note that the temperature of the Sun is 5,800 K.

Star A is a red star. Star B is a blue star. You are able to determine that both stars are the same size. Which star is more luminous?

Parallax is used to measure a star's:

Figure 1 -Figure 1 shows an H-R diagram, with five stars labeled A through E. Which star has the largest luminosity?

Explain how astronomers can use the blue and visual filters to determine the temperatures of stars.

What is the spectral type of stars that have the strongest hydrogen absorption lines? Why do stars that are hotter than these have weaker hydrogen lines?

How is the unit of length known as a parsec defined?

Along the main sequence, how do the luminosity, temperature, radius, and mass of stars change as you go from the upper-left to the lower-right corners of the H-R diagram?

A parsec is a unit of time.

Stars are made mostly of:

Eclipsing binary systems:

What is the approximate luminosity of a 5 M ⊙\odot⊙ main-sequence star?

Why Learn Astronomy

Patterns in the Skymotions of Earth

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Birth and Evolution of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquid the Giant Planets

Planetary Adornmentsmoons and Rings

Dwarf Planets and Small Solar System Bodies

Our Starthe Sun

Star Formation and the Interstellar Medium

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Relativity and Black Holes

The Expanding Universe

Galaxies

The Milky Waya Normal Spiral Galaxy

Modern Cosmology

Large-Scale Structure in the Universe

Life

Filters

The bright star named Rigel has a luminosity of 66,000 L _$\wedge$ and a temperature of 11,000 K. What is its radius? Note that the temperature of the Sun is 5,800 K.

What is the approximate luminosity of a 5 M _$\odot$ main-sequence star?