Question 1

Why is luminosity an inverse-square law?

Accepted Answer

With greater distance from the star,its light is spread over a larger area and its apparent brightness is less.Because total surface area of a sphere is proportional to the distance squared,this is where the squared part of the relationship is derived.The inverse relationship is because the farther away you get from the source,the dimmer the object appears.

Question 2

The spectral luminosity class of the star Spica is B1 V,and that of the star $\tau$ Ceti is G8 V.From this (with luminosity measured in solar luminosities),we know for sure that

Accepted Answer

A)  "$\tau$ Ceti is hotter but has the same luminosity as Spica." 
B)  "$\tau$ Ceti is cooler but has the same luminosity as Spica." 
C)  "$\tau$ Ceti is cooler and has a lower luminosity than Spica." 
D)  "$\tau$ Ceti is hotter and has a lower luminosity than Spica." 
A)  "$\tau$ Ceti is hotter but has the same luminosity as Spica." 
B)  "$\tau$ Ceti is cooler but has the same luminosity as Spica." 
C)  "$\tau$ Ceti is cooler and has a lower luminosity than Spica." 
D)  "$\tau$ Ceti is hotter and has a lower luminosity than Spica." C

Question 3

The key to finding a star's radius from its luminosity and surface temperature is the Stefan-Boltzmann law.

Accepted Answer

A) True 
 B)False  True

Question 4

Of two stars of spectral class B5,one has broad hydrogen lines and the other has narrow hydrogen lines.How do these stars differ physically?

Accepted Answer

A)  The star with the narrow lines is a main-sequence star,and the star with the broad lines is a giant or supergiant. 
B)  The star with the narrow lines is a hot star,and the star with the broad lines is a cool star. 
C)  The star with the narrow lines is a giant or supergiant,and the star with the broad lines is a main-sequence star. 
D)  The star with the narrow lines is a cool star,and the star with the broad lines is a hot star. 
A)  The star with the narrow lines is a main-sequence star,and the star with the broad lines is a giant or supergiant. 
B)  The star with the narrow lines is a hot star,and the star with the broad lines is a cool star. 
C)  The star with the narrow lines is a giant or supergiant,and the star with the broad lines is a main-sequence star. 
D)  The star with the narrow lines is a cool star,and the star with the broad lines is a hot star.

Question 5

Where do we find the most massive stars on the main sequence in a Hertzsprung-Russell diagram?

Accepted Answer

A)  Upper left 
B)  They all have approximately the same mass because this is what defines the main sequence. 
C)  Lower right 
D)  Center,with lower mass stars on either side 
A)  Upper left 
B)  They all have approximately the same mass because this is what defines the main sequence. 
C)  Lower right 
D)  Center,with lower mass stars on either side

Question 6

Stars of spectral class K compared to stars of spectral class G are

Accepted Answer

A)  bigger. 
B)  smaller. 
C)  hotter. 
D)  cooler. 
A)  bigger. 
B)  smaller. 
C)  hotter. 
D)  cooler.

Question 7

What is the only way to measure the mass of a star accurately?

Accepted Answer

A)  Measure its gravitational effect on another object. 
B)  Measure its spectral type and luminosity class,then use the H-R diagram. 
C)  It is not possible to measure the mass of a star. 
D)  Measure its distance using trigonometric parallax and its brightness using photometry. 
A)  Measure its gravitational effect on another object. 
B)  Measure its spectral type and luminosity class,then use the H-R diagram. 
C)  It is not possible to measure the mass of a star. 
D)  Measure its distance using trigonometric parallax and its brightness using photometry.

Question 8

Spectral classification determines a nearby star's surface temperature by examining the

Accepted Answer

A)  peak wavelength of the star spectrum. 
B)  relative intensities of light measured through different wavelength band filters. 
C)  pattern of spectral "absorption" lines from various atoms. 
D)  the overall shape of the star's spectrum compared to a black body. 
A)  peak wavelength of the star spectrum. 
B)  relative intensities of light measured through different wavelength band filters. 
C)  pattern of spectral "absorption" lines from various atoms. 
D)  the overall shape of the star's spectrum compared to a black body.

Question 9

At what distance are stars from Earth if the apparent magnitude equals their absolute magnitude?

Accepted Answer

A)  10 ly 
B)  10 parsecs 
C)  10 AU 
D)  1 ly 
A)  10 ly 
B)  10 parsecs 
C)  10 AU 
D)  1 ly

Question 10

What makes stellar magnitude unusual as a scale of brightness of stars?

Accepted Answer

512 times

Question 11

Which of the following four spectral classifications represents the hottest stellar surface temperature?

Accepted Answer

A)  K 
B)  A 
C)  G 
D)  B 
A)  K 
B)  A 
C)  G 
D)  B

Question 12

If the Hipparcos satellite measures the parallax motion of a star against the background stars and concludes that the star has a parallax of 0.004 arcsec,how far is that star from Earth?

Accepted Answer

A)  250 pc or 800 ly 
B)  0.004 pc or 0.013 ly 
C)  25 pc or 81 ly 
D)  400 pc or 1300 ly 
A)  250 pc or 800 ly 
B)  0.004 pc or 0.013 ly 
C)  25 pc or 81 ly 
D)  400 pc or 1300 ly

Question 13

A few rare stars are considerably bigger and brighter than typical giants,with up to 1000 solar radii,and are called supergiants.

Accepted Answer

A) True 
 B)False

Question 14

Stars of luminosity class V compared to stars of luminosity class III are

Accepted Answer

A)  bigger. 
B)  smaller. 
C)  hotter. 
D)  cooler. 
A)  bigger. 
B)  smaller. 
C)  hotter. 
D)  cooler.

Question 15

Without a telescope,the brightest stars are magnitude 6 stars and the dimmest stars are magnitude 1 stars.

Accepted Answer

A) True 
 B)False

Question 16

What is the size of a star in the upper right part of the Hertzsprung-Russell diagram compared to one in the middle of the diagram?

Accepted Answer

A)  It is fainter. 
B)  It is hotter. 
C)  There are no stars in the upper right part of the diagram. 
D)  It is larger. 
A)  It is fainter. 
B)  It is hotter. 
C)  There are no stars in the upper right part of the diagram. 
D)  It is larger.

Question 17

If you compare two stars,the one with the

Accepted Answer

A)  larger radius must have the greater luminosity. 
B)  higher surface temperature must have the greater luminosity. 
C)  smaller absolute magnitude must have the greater luminosity. 
D)  larger surface area has the greater energy flux from its surface. 
A)  larger radius must have the greater luminosity. 
B)  higher surface temperature must have the greater luminosity. 
C)  smaller absolute magnitude must have the greater luminosity. 
D)  larger surface area has the greater energy flux from its surface.

Question 18

Stellar parallax exists because

Accepted Answer

A)  Earth moves in space. 
B)  stars move in space. 
C)  Earth rotates about its own axis. 
D)  stars have size (they are not really just points of light). 
A)  Earth moves in space. 
B)  stars move in space. 
C)  Earth rotates about its own axis. 
D)  stars have size (they are not really just points of light).

Question 19

Spectroscopic parallax is the

Accepted Answer

A)  apparent change in position of the absorption lines in a star's spectrum due to the Doppler shift,caused by Earth's motion around the Sun. 
B)  apparent change in position of a nearby star compared to distant background stars,due to the motion of Earth around the Sun. 
C)  change in position of the absorption lines in a star's spectrum due to the Doppler shift,caused by the star's motion around the center of mass in a binary star system. 
D)  distance to a star measured using the spectral luminosity class of the star and the inverse-square law. 
A)  apparent change in position of the absorption lines in a star's spectrum due to the Doppler shift,caused by Earth's motion around the Sun. 
B)  apparent change in position of a nearby star compared to distant background stars,due to the motion of Earth around the Sun. 
C)  change in position of the absorption lines in a star's spectrum due to the Doppler shift,caused by the star's motion around the center of mass in a binary star system. 
D)  distance to a star measured using the spectral luminosity class of the star and the inverse-square law.

Question 20

A magnitude +4 star is twice as bright as a magnitude +2 star.

Accepted Answer

A) True 
 B)False

Why is luminosity an inverse-square law?

The spectral luminosity class of the star Spica is B1 V,and that of the star $\tau$ Ceti is G8 V.From this (with luminosity measured in solar luminosities),we know for sure that

The key to finding a star's radius from its luminosity and surface temperature is the Stefan-Boltzmann law.

Of two stars of spectral class B5,one has broad hydrogen lines and the other has narrow hydrogen lines.How do these stars differ physically?

Where do we find the most massive stars on the main sequence in a Hertzsprung-Russell diagram?

Stars of spectral class K compared to stars of spectral class G are

What is the only way to measure the mass of a star accurately?

Spectral classification determines a nearby star's surface temperature by examining the

At what distance are stars from Earth if the apparent magnitude equals their absolute magnitude?

What makes stellar magnitude unusual as a scale of brightness of stars?

Which of the following four spectral classifications represents the hottest stellar surface temperature?

If the Hipparcos satellite measures the parallax motion of a star against the background stars and concludes that the star has a parallax of 0.004 arcsec,how far is that star from Earth?

A few rare stars are considerably bigger and brighter than typical giants,with up to 1000 solar radii,and are called supergiants.

Stars of luminosity class V compared to stars of luminosity class III are

Without a telescope,the brightest stars are magnitude 6 stars and the dimmest stars are magnitude 1 stars.

What is the size of a star in the upper right part of the Hertzsprung-Russell diagram compared to one in the middle of the diagram?

If you compare two stars,the one with the

Stellar parallax exists because

Spectroscopic parallax is the

A magnitude +4 star is twice as bright as a magnitude +2 star.

Predicting the Motions of the Stars, Sun, and Moon

Decoding the Hidden Messages in Starlight

Analyzing Scales and Motions of the Universe

Exploring Our Evolving Solar System

Uncovering Earths Systems

Exploring Terrestrial Surface Processes and Atmospheres

Observing the Dynamic Giant Planets

Looking for Life Beyond Earth

Probing the Dynamic Sun

Inferring Patterns in Star Life Cycles

Predicting the Violent End of the Largest Stars

Exploring Our Galaxy

Investigating Other Galaxies

Observing the Evolution of the Universe

Filters

Exam 10: Observing Properties of Distant Stars

Why is luminosity an inverse-square law?

The spectral luminosity class of the star Spica is B1 V,and that of the star τ\tauτ Ceti is G8 V.From this (with luminosity measured in solar luminosities),we know for sure that

The key to finding a star's radius from its luminosity and surface temperature is the Stefan-Boltzmann law.

Of two stars of spectral class B5,one has broad hydrogen lines and the other has narrow hydrogen lines.How do these stars differ physically?

Where do we find the most massive stars on the main sequence in a Hertzsprung-Russell diagram?

Stars of spectral class K compared to stars of spectral class G are

What is the only way to measure the mass of a star accurately?

Spectral classification determines a nearby star's surface temperature by examining the

At what distance are stars from Earth if the apparent magnitude equals their absolute magnitude?

What makes stellar magnitude unusual as a scale of brightness of stars?

Which of the following four spectral classifications represents the hottest stellar surface temperature?

If the Hipparcos satellite measures the parallax motion of a star against the background stars and concludes that the star has a parallax of 0.004 arcsec,how far is that star from Earth?

A few rare stars are considerably bigger and brighter than typical giants,with up to 1000 solar radii,and are called supergiants.

Stars of luminosity class V compared to stars of luminosity class III are

Without a telescope,the brightest stars are magnitude 6 stars and the dimmest stars are magnitude 1 stars.

What is the size of a star in the upper right part of the Hertzsprung-Russell diagram compared to one in the middle of the diagram?

If you compare two stars,the one with the

Stellar parallax exists because

Spectroscopic parallax is the

A magnitude +4 star is twice as bright as a magnitude +2 star.

Predicting the Motions of the Stars, Sun, and Moon

Decoding the Hidden Messages in Starlight

Analyzing Scales and Motions of the Universe

Exploring Our Evolving Solar System

Uncovering Earths Systems

Exploring Terrestrial Surface Processes and Atmospheres

Observing the Dynamic Giant Planets

Looking for Life Beyond Earth

Probing the Dynamic Sun

Inferring Patterns in Star Life Cycles

Predicting the Violent End of the Largest Stars

Exploring Our Galaxy

Investigating Other Galaxies

Observing the Evolution of the Universe

Filters

The spectral luminosity class of the star Spica is B1 V,and that of the star $\tau$ Ceti is G8 V.From this (with luminosity measured in solar luminosities),we know for sure that