Question 1

By approximately how many magnitudes is the star Sirius fainter than the full moon in our sky? (See Figure 17-6.(in the text))

Accepted Answer

A) 2 
B) 5 
C) 15 
D) 11 
A) 2 
B) 5 
C) 15 
D) 11

Question 2

How many stars (other than the Sun) have a stellar parallax greater than 1 second of arc?

Accepted Answer

A) over 100 
B) 1 
C) 0 
D) 8 
A) over 100 
B) 1 
C) 0 
D) 8

Question 3

Proper motion of a star is defined as its:

Accepted Answer

A) apparent motion toward or away from us, measured by the Doppler shift of its spectral lines. 
B) apparent motion against the background stars as a consequence of Earth's orbital motion around the Sun. 
C) real motion in three-dimensional space. 
D) apparent motion across our sky against the background stars. 
A) apparent motion toward or away from us, measured by the Doppler shift of its spectral lines. 
B) apparent motion against the background stars as a consequence of Earth's orbital motion around the Sun. 
C) real motion in three-dimensional space. 
D) apparent motion across our sky against the background stars.

Question 4

On the basis of the graph of absorption line strengths (in Figure 17-12), what is the spectral type of a star with the following spectral pattern: very strong Ca II lines; weaker Fe I lines; equal strength but weaker Fe II and Ca I lines; and no He I, He II, or TiO lines?

Accepted Answer

A) A 
B) F 
C) K 
D) O 
A) A 
B) F 
C) K 
D) O

Question 5

Stellar parallax is the:

Accepted Answer

A) elliptical motion of a star in a binary system, as the two stars orbit around each other. 
B) difference between the apparent magnitude and the absolute magnitude of a star. 
C) assumed change in the distance to a star when it dims, as it passes through an interstellar cloud. 
D) apparent shift in the position of a nearby star because of Earth's motion. 
A) elliptical motion of a star in a binary system, as the two stars orbit around each other. 
B) difference between the apparent magnitude and the absolute magnitude of a star. 
C) assumed change in the distance to a star when it dims, as it passes through an interstellar cloud. 
D) apparent shift in the position of a nearby star because of Earth's motion.

Question 6

As the spectral classification changes from F1 to F9, the main change in the star being characterized is that it becomes:

Accepted Answer

A) hotter. 
B) cooler. 
C) larger. 
D) younger. 
A) hotter. 
B) cooler. 
C) larger. 
D) younger.

Question 7

Betelgeuse (the bright star in the shoulder of the constellation Orion) has a surface temperature of 3500 K and a luminosity 100,000 times that of the Sun. What is its approximate radius in terms of that of the Sun? (See Figure 17-15.(in the text))

Accepted Answer

A) the same 
B) 1000 times larger 
C) 100 times larger 
D) 10 times larger 
A) the same 
B) 1000 times larger 
C) 100 times larger 
D) 10 times larger

Question 8

If the two stars in a binary system were moved farther apart, what would happen to the period of their motion?

Accepted Answer

A) The period would increase. 
B) The period would decrease. 
C) The period would be unchanged. 
D) The orbital dimension is determined by the masses. If the dimension is changed without changing the masses, the motion will become aperiodic. 
A) The period would increase. 
B) The period would decrease. 
C) The period would be unchanged. 
D) The orbital dimension is determined by the masses. If the dimension is changed without changing the masses, the motion will become aperiodic.

Question 9

For a main-sequence star with the same radius as the Sun, a surface temperature of 5000 K gives about half the Sun's luminosity. What would a surface temperature of 20,000 K give for the approximate luminosity of a solar mass star?

Accepted Answer

A) 0.5 $L_{\odot}$ 
B) 4 $L_{\odot}$ 
C) 16 $L_{\odot}$ 
D) 140 $L_{\odot}$ 
A) 0.5 $L_{\odot}$ 
B) 4 $L_{\odot}$ 
C) 16 $L_{\odot}$ 
D) 140 $L_{\odot}$

Question 10

A particular star is found to have a very faint companion. When the spectrum of the companion is photographed and analyzed, it is found to contain absorption features of neutral potassium (K) and water (H2O). Based on this information, the companion is a brown dwarf of spectral class:

Accepted Answer

A) T. 
B) L. 
C) K. 
D) M. 
A) T. 
B) L. 
C) K. 
D) M.

Question 11

From which feature of light from a nearby star is the surface temperature determined most precisely?

Accepted Answer

A) relative distribution of the continuum light in the spectrum 
B) relative strengths of emission lines in its spectrum 
C) relative strengths of absorption lines from different atoms (e.g., H, Ca) and molecules (e.g., TiO) 
D) Doppler shift of its spectral lines 
A) relative distribution of the continuum light in the spectrum 
B) relative strengths of emission lines in its spectrum 
C) relative strengths of absorption lines from different atoms (e.g., H, Ca) and molecules (e.g., TiO) 
D) Doppler shift of its spectral lines

Question 12

The following are parameters of stars that astronomers obtained from their measurements. Which one of these conclusions is obviously erroneous, on the basis of the positions of these alleged stars on the Hertzsprung-Russell diagram in Figure 17-15a? ( $L_{\odot}$ and $R_{\odot}$ are the luminosity and radius of the Sun, respectively.)

Accepted Answer

A) luminosity = 1 $L_{\odot}$ , radius = 1/10 $R_{\odot}$ , temperature = 20,000 K; conclusion: white dwarf star 
B) luminosity = 1/100 $L_{\odot}$ , radius = 1/100 $R_{\odot}$ , temperature = 20,000 K; conclusion: white dwarf star 
C) luminosity ? 104 $L_{\odot}$ , radius $R_{\odot}$ 100 ? , temperature 5000 K; conclusion: a supergiant star 
D) luminosity = 1 $L_{\odot}$ , radius = 1 $R_{\odot}$ , temperature = 6000 K; conclusion: main-sequence star 
A) luminosity = 1 $L_{\odot}$ , radius = 1/10 $R_{\odot}$ , temperature = 20,000 K; conclusion: white dwarf star 
B) luminosity = 1/100 $L_{\odot}$ , radius = 1/100 $R_{\odot}$ , temperature = 20,000 K; conclusion: white dwarf star 
C) luminosity ? 104 $L_{\odot}$ , radius $R_{\odot}$ 100 ? , temperature 5000 K; conclusion: a supergiant star 
D) luminosity = 1 $L_{\odot}$ , radius = 1 $R_{\odot}$ , temperature = 6000 K; conclusion: main-sequence star

Question 13

Measurements of the brightness of a distant star through the three appropriate filters indicate that the star is brightest in U, less bright in B, and faintest in V. What conclusion can be drawn from this information, assuming no absorption of light between the star and Earth?

Accepted Answer

A) This information is insufficient to allow a conclusion to be drawn about star surface temperature. 
B) The star has an intermediate temperature, close to the Sun. 
C) The star has a very low surface temperature. 
D) The star has a very high surface temperature. 
A) This information is insufficient to allow a conclusion to be drawn about star surface temperature. 
B) The star has an intermediate temperature, close to the Sun. 
C) The star has a very low surface temperature. 
D) The star has a very high surface temperature.

By approximately how many magnitudes is the star Sirius fainter than the full moon in our sky? (See Figure 17-6.(in the text))

How many stars (other than the Sun) have a stellar parallax greater than 1 second of arc?

Proper motion of a star is defined as its:

On the basis of the graph of absorption line strengths (in Figure 17-12), what is the spectral type of a star with the following spectral pattern: very strong Ca II lines; weaker Fe I lines; equal strength but weaker Fe II and Ca I lines; and no He I, He II, or TiO lines?

Stellar parallax is the:

As the spectral classification changes from F1 to F9, the main change in the star being characterized is that it becomes:

Betelgeuse (the bright star in the shoulder of the constellation Orion) has a surface temperature of 3500 K and a luminosity 100,000 times that of the Sun. What is its approximate radius in terms of that of the Sun? (See Figure 17-15.(in the text))

If the two stars in a binary system were moved farther apart, what would happen to the period of their motion?

For a main-sequence star with the same radius as the Sun, a surface temperature of 5000 K gives about half the Sun's luminosity. What would a surface temperature of 20,000 K give for the approximate luminosity of a solar mass star?

A particular star is found to have a very faint companion. When the spectrum of the companion is photographed and analyzed, it is found to contain absorption features of neutral potassium (K) and water (H₂O). Based on this information, the companion is a brown dwarf of spectral class:

From which feature of light from a nearby star is the surface temperature determined most precisely?

Measurements of the brightness of a distant star through the three appropriate filters indicate that the star is brightest in U, less bright in B, and faintest in V. What conclusion can be drawn from this information, assuming no absorption of light between the star and Earth?

Astronomy and the Universe

Knowing the Heavens

Eclipses and the Motion of the Moon

Gravitation and the Waltz of the Planets

The Nature of Light

Optics and Telescopes

Comparative Planetology I: Our Solar System

Comparative Planetology II: the Origin of Our Solar System

The Living Earth

Our Barren Moon

Mercury, Venus, and Mars: Terrestrial, yet Unique

Jupiter and Saturn: Lords of the Planets

Jupiter and Saturns Satellites of Fire and Ice

Uranus, Neptune, Pluto, and the Kuiper Belt: Remote Worlds

Asteroids, Comets, and Impacts

Our Star, the Sun

The Birth of Stars

Stellar Evolution: on and After the Main Sequence

Stellar Evolution: The Death of Stars

Stellar Remnants: Neutron Stars and Black Holes

Our Galaxy

Galaxies

Quasars and Active Galaxies

Cosmology: The Origin and Evolution of the Universe

Exploring the Early Universe

The Search for Extraterrestrial Life

Filters

Exam 17: The Nature of the Stars

By approximately how many magnitudes is the star Sirius fainter than the full moon in our sky? (See Figure 17-6.(in the text))

How many stars (other than the Sun) have a stellar parallax greater than 1 second of arc?

Proper motion of a star is defined as its:

On the basis of the graph of absorption line strengths (in Figure 17-12), what is the spectral type of a star with the following spectral pattern: very strong Ca II lines; weaker Fe I lines; equal strength but weaker Fe II and Ca I lines; and no He I, He II, or TiO lines?

Stellar parallax is the:

As the spectral classification changes from F1 to F9, the main change in the star being characterized is that it becomes:

Betelgeuse (the bright star in the shoulder of the constellation Orion) has a surface temperature of 3500 K and a luminosity 100,000 times that of the Sun. What is its approximate radius in terms of that of the Sun? (See Figure 17-15.(in the text))

If the two stars in a binary system were moved farther apart, what would happen to the period of their motion?

For a main-sequence star with the same radius as the Sun, a surface temperature of 5000 K gives about half the Sun's luminosity. What would a surface temperature of 20,000 K give for the approximate luminosity of a solar mass star?

A particular star is found to have a very faint companion. When the spectrum of the companion is photographed and analyzed, it is found to contain absorption features of neutral potassium (K) and water (H2O). Based on this information, the companion is a brown dwarf of spectral class:

From which feature of light from a nearby star is the surface temperature determined most precisely?

Measurements of the brightness of a distant star through the three appropriate filters indicate that the star is brightest in U, less bright in B, and faintest in V. What conclusion can be drawn from this information, assuming no absorption of light between the star and Earth?

Astronomy and the Universe

Knowing the Heavens

Eclipses and the Motion of the Moon

Gravitation and the Waltz of the Planets

The Nature of Light

Optics and Telescopes

Comparative Planetology I: Our Solar System

Comparative Planetology II: the Origin of Our Solar System

The Living Earth

Our Barren Moon

Mercury, Venus, and Mars: Terrestrial, yet Unique

Jupiter and Saturn: Lords of the Planets

Jupiter and Saturns Satellites of Fire and Ice

Uranus, Neptune, Pluto, and the Kuiper Belt: Remote Worlds

Asteroids, Comets, and Impacts

Our Star, the Sun

The Birth of Stars

Stellar Evolution: on and After the Main Sequence

Stellar Evolution: The Death of Stars

Stellar Remnants: Neutron Stars and Black Holes

Our Galaxy

Galaxies

Quasars and Active Galaxies

Cosmology: The Origin and Evolution of the Universe

Exploring the Early Universe

The Search for Extraterrestrial Life

Filters

A particular star is found to have a very faint companion. When the spectrum of the companion is photographed and analyzed, it is found to contain absorption features of neutral potassium (K) and water (H₂O). Based on this information, the companion is a brown dwarf of spectral class: