Question 1

What is the main property of a main-sequence star that determines all its other properties?

Accepted Answer

The star's mass has

Question 2

You discover a binary star system in which star A has a velocity of 10 km/s and star B has a velocity of 30 km/s.If you study the system further and find out that the orbital period is 30 days and the orbital separation is a constant 0.3 AU, then what are the masses of stars A and B?

Accepted Answer

A)  Star A is 3MSUN, and star B is 1MSUN. 
B)  Star A is 1MSUN, and star B is 0.3MSUN. 
C)  Star A is 6MSUN, and star B is 2MSUN. 
D)  Star A is 2MSUN, and star B is 0.5MSUN. 
E)  Star A is 0.3MSUN, and star B is 1MSUN. 
A)  Star A is 3MSUN, and star B is 1MSUN. 
B)  Star A is 1MSUN, and star B is 0.3MSUN. 
C)  Star A is 6MSUN, and star B is 2MSUN. 
D)  Star A is 2MSUN, and star B is 0.5MSUN. 
E)  Star A is 0.3MSUN, and star B is 1MSUN.

Question 3

If a star's measured parallax is 0.2 arcsec, what is its distance?

Accepted Answer

A)  2 pc 
B)  5 pc 
C)  20 pc 
D)  40 pc 
E)  50 pc 
A)  2 pc 
B)  5 pc 
C)  20 pc 
D)  40 pc 
E)  50 pc

Question 4

You observe a binary star system and find that star 1 has a velocity of 20 m/s while star 2 has a velocity of 40 m/s.What is the ratio of masses of the two stars (M1/M2)? If you find that the separation of the two stars is 0.5 AU and the orbital period is 70 days, then what are the individual masses of the two stars?

Accepted Answer

The ratio of masses of stars in a binary

Question 5

When main-sequence stars are plotted on an H-R diagram (luminosity vs.temperature), they fall along a swath running diagonally from the upper left to the lower right.Why don't they fall in arbitrary locations on the HR diagram?

Accepted Answer

The mass of a star determines

Question 6

Which spectral type has the strongest hydrogen absorption lines?

Accepted Answer

A)  O 
B)  B 
C)  A 
D)  G 
E)  M 
A)  O 
B)  B 
C)  A 
D)  G 
E)  M

Question 7

If we know the temperature and luminosity of a star, we can also calculate its

Accepted Answer

A)  radius. 
B)  mass. 
C)  chemical composition. 
D)  brightness. 
E)  all of the above 
A)  radius. 
B)  mass. 
C)  chemical composition. 
D)  brightness. 
E)  all of the above

Question 8

Stars that have spectral type B ________ in temperature compared with stars that have spectral type M.

Accepted Answer

A)  are cooler 
B)  are hotter 
C)  are the same 
D)  usually hotter but sometimes cooler 
E)  usually cooler but sometimes hotter 
A)  are cooler 
B)  are hotter 
C)  are the same 
D)  usually hotter but sometimes cooler 
E)  usually cooler but sometimes hotter

Question 9

The bright star Arcturus has a luminosity of 210 LSUN and a temperature of 4300 K.What is its radius? Note that the Sun has a temperature of 5800 K.

Accepted Answer

Using the Stefan-Boltzmann law

Question 10

Which of the following is directly measurable from the absorption lines of a star?

Accepted Answer

A)  the luminosity of the star 
B)  the chemical composition of the star 
C)  the mass of the star 
D)  the distance to the star 
E)  the age of the star 
A)  the luminosity of the star 
B)  the chemical composition of the star 
C)  the mass of the star 
D)  the distance to the star 
E)  the age of the star

Question 11

Which properties can be plotted on the horizontal axis of an H-R diagram?

Accepted Answer

A)  luminosity, apparent magnitude, and absolute magnitude 
B)  luminosity, color, and spectral class 
C)  temperature, color, and spectral class 
D)  temperature and luminosity 
E)  spectral class only 
A)  luminosity, apparent magnitude, and absolute magnitude 
B)  luminosity, color, and spectral class 
C)  temperature, color, and spectral class 
D)  temperature and luminosity 
E)  spectral class only

Question 12

Based on the figure shown below, approximately how many times more luminous is a main-sequence star having a radius of 10 RSUN than a star having a radius of 1 RSUN?

Accepted Answer

From the mass-radius graph,the mass of a

Question 13

Binary star systems are extremely useful in studying stars because they allow us to determine star

Accepted Answer

A)  temperatures. 
B)  sizes. 
C)  masses. 
D)  distances. 
E)  spectral types. 
A)  temperatures. 
B)  sizes. 
C)  masses. 
D)  distances. 
E)  spectral types.

Question 14

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 15

The figure below shows an H-R diagram, with five stars labeled A through E.Which star has the highest temperature?

Accepted Answer

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

Question 16

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 17

The absolute magnitude of a star is a measure of its

Accepted Answer

A)  luminosity. 
B)  composition. 
C)  distance. 
D)  color. 
E)  radius. 
A)  luminosity. 
B)  composition. 
C)  distance. 
D)  color. 
E)  radius.

Question 18

The one property of a main-sequence star that determines all its other properties is its

Accepted Answer

A)  luminosity. 
B)  mass. 
C)  temperature. 
D)  spectral type. 
E)  brightness. 
A)  luminosity. 
B)  mass. 
C)  temperature. 
D)  spectral type. 
E)  brightness.

Question 19

Two main-sequence stars have the same temperature.If star A is four times more luminous than star B, then

Accepted Answer

A)  star B is two times farther away than star A. 
B)  star B is four times farther away than star A. 
C)  star B is eight times farther away than star A. 
D)  star B and star A lie at the same distance from us. 
E)  it is impossible to determine their relative distances from the information given. 
A)  star B is two times farther away than star A. 
B)  star B is four times farther away than star A. 
C)  star B is eight times farther away than star A. 
D)  star B and star A lie at the same distance from us. 
E)  it is impossible to determine their relative distances from the information given.

Question 20

What relationship exists between a star's distance and its parallax?

Accepted Answer

A)  Distance is directly proportional to parallax. 
B)  Distance is inversely proportional to parallax. 
C)  Distance is directly proportional to parallax squared. 
D)  Distance is inversely proportional to parallax squared. 
E)  Distance and parallax are not related to each other at all. 
A)  Distance is directly proportional to parallax. 
B)  Distance is inversely proportional to parallax. 
C)  Distance is directly proportional to parallax squared. 
D)  Distance is inversely proportional to parallax squared. 
E)  Distance and parallax are not related to each other at all.

Exam 13: Taking the Measure of Stars

What is the main property of a main-sequence star that determines all its other properties?

You discover a binary star system in which star A has a velocity of 10 km/s and star B has a velocity of 30 km/s.If you study the system further and find out that the orbital period is 30 days and the orbital separation is a constant 0.3 AU, then what are the masses of stars A and B?

If a star's measured parallax is 0.2 arcsec, what is its distance?

When main-sequence stars are plotted on an H-R diagram (luminosity vs.temperature), they fall along a swath running diagonally from the upper left to the lower right.Why don't they fall in arbitrary locations on the HR diagram?

Which spectral type has the strongest hydrogen absorption lines?

If we know the temperature and luminosity of a star, we can also calculate its

Stars that have spectral type B ________ in temperature compared with stars that have spectral type M.

The bright star Arcturus has a luminosity of 210 LSUN and a temperature of 4300 K.What is its radius? Note that the Sun has a temperature of 5800 K.

Which of the following is directly measurable from the absorption lines of a star?

Which properties can be plotted on the horizontal axis of an H-R diagram?

Based on the figure shown below, approximately how many times more luminous is a main-sequence star having a radius of 10 RSUN than a star having a radius of 1 RSUN?

Binary star systems are extremely useful in studying stars because they allow us to determine star

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?

The figure below shows an H-R diagram, with five stars labeled A through E.Which star has the highest temperature?

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

The absolute magnitude of a star is a measure of its

The one property of a main-sequence star that determines all its other properties is its

Two main-sequence stars have the same temperature.If star A is four times more luminous than star B, then

What relationship exists between a star's distance and its parallax?

Thinking Like an Astronomer

Patterns in the Skymotions of Earth and the Moon

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Formation of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquidthe Giant Planets

Planetary Moons and Rings

Dwarf Planets and Small Solar System Bodies

Our Starthe Sun

The Interstellar Medium and Star Formation

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Relativity and Black Holes

Galaxies

The Milky Waya Normal Spiral Galaxy

The Expanding Universe

Cosmology

Large-Scale Structure in the Universe

Life

Filters

The bright star Arcturus has a luminosity of 210 L_SUN and a temperature of 4300 K.What is its radius? Note that the Sun has a temperature of 5800 K.

Based on the figure shown below, approximately how many times more luminous is a main-sequence star having a radius of 10 R_SUN than a star having a radius of 1 R_SUN?