Question 1

Suppose it is discovered that the earliest galaxies were flocculent spirals. What implications might this have?

Accepted Answer

A) Flocculent spirals always evolve into grand design spirals. 
B) The early universe was chaotic. 
C) The stars in these early spirals formed first before the galaxies themselves (and their spiral arms). 
D) The early universe was metal poor. 
A) Flocculent spirals always evolve into grand design spirals. 
B) The early universe was chaotic. 
C) The stars in these early spirals formed first before the galaxies themselves (and their spiral arms). 
D) The early universe was metal poor.

Question 2

High-velocity stars are isolated stars that swing in and out of the plane of the galaxy at relatively high velocities with respect to the solar system. Where would you expect to find them?

Accepted Answer

A) moving rapidly toward the solar system from all directions because of cosmic explosions in the open clusters where they are produced 
B) in the rotating disk of the galaxy, having relatively large velocities with respect to the solar system because of their positions in the disk 
C) in orbit around the galactic halo 
D) circling the entire galaxy, just outside the galactic plane 
A) moving rapidly toward the solar system from all directions because of cosmic explosions in the open clusters where they are produced 
B) in the rotating disk of the galaxy, having relatively large velocities with respect to the solar system because of their positions in the disk 
C) in orbit around the galactic halo 
D) circling the entire galaxy, just outside the galactic plane

Question 3

Harlow Shapley determined the position of the Sun in the galaxy by measuring the distances to 93 globular clusters of stars. How did Shapley obtain the distances to these very distant clusters?

Accepted Answer

A) He measured the apparent brightness and pulsation periods of RR Lyrae stars in the clusters. 
B) He plotted the apparent brightness and spectral classes of a sample of the stars in each cluster on a Hertzsprung-Russell diagram. 
C) He measured the proper motion and radial velocity of each globular cluster. 
D) He measured the apparent brightness of the brightest red giant stars in each cluster. 
A) He measured the apparent brightness and pulsation periods of RR Lyrae stars in the clusters. 
B) He plotted the apparent brightness and spectral classes of a sample of the stars in each cluster on a Hertzsprung-Russell diagram. 
C) He measured the proper motion and radial velocity of each globular cluster. 
D) He measured the apparent brightness of the brightest red giant stars in each cluster.

Question 4

If you want to find the distribution of stars in the Milky Way Galaxy, you should observe in which portion of the spectrum?

Accepted Answer

A) x ray 
B) near infrared 
C) far infrared 
D) radio 
A) x ray 
B) near infrared 
C) far infrared 
D) radio

Question 5

Because the rotation curve for the Milky Way Galaxy is approximately flat, a star in a circular orbit 13 kpc from the galactic center has the same orbital speed as the Sun, namely 220 km/sec. How much mass is interior to this star's orbit (in solar masses)?

Accepted Answer

A) 9.0 × 1010 
B) 1.5 × 1011 
C) 9.0 × 1011 
D) 1.5 × 1012 
A) 9.0 × 1010 
B) 1.5 × 1011 
C) 9.0 × 1011 
D) 1.5 × 1012

Question 6

Which physical process is thought to have created the Local Bubble near our Sun in the galaxy?

Accepted Answer

A) a nearby supernova explosion 
B) Neanderthal campfires 
C) the solar wind 
D) hot O and B stars in the solar neighborhood 
A) a nearby supernova explosion 
B) Neanderthal campfires 
C) the solar wind 
D) hot O and B stars in the solar neighborhood

Question 7

A Cepheid variable star is seen to vary regularly with a period of 25 days. How many times more luminous than the Sun would this star appear to be if it were to replace the Sun in our solar system? (See Figure 22-4 of Universe, 11th ed.)
  ​

Accepted Answer

A) 4 
B) 10,000 
C) 1000 
D) 100 
A) 4 
B) 10,000 
C) 1000 
D) 100

Question 8

Gamma-ray "bubbles" have been found above and below the plane of our galaxy. (See Figure 22-30 of Universe, 11th ed.) These are:
  ​

Accepted Answer

A) relatively small regions within the central bulge that are probably remnants of jet activity from Sagittarius A*. 
B) regions from which no gamma-ray emission has been observed. 
C) huge regions in which gamma rays are produced when high-speed electrons interact with photons of energies below the gamma-ray range. 
D) the first gamma-ray bursters to be observed within our galaxy. 
A) relatively small regions within the central bulge that are probably remnants of jet activity from Sagittarius A*. 
B) regions from which no gamma-ray emission has been observed. 
C) huge regions in which gamma rays are produced when high-speed electrons interact with photons of energies below the gamma-ray range. 
D) the first gamma-ray bursters to be observed within our galaxy.

Question 9

The neutrino has been proposed as a dark matter candidate. What is the current status of this idea?

Accepted Answer

A) It is still a viable candidate. 
B) It has been rejected, because it is not massive enough. 
C) It has been rejected, because it cannot "clump" to form the dark matter halo of our galaxy. 
D) It has been rejected, because it has been found to be an unstable particle. 
A) It is still a viable candidate. 
B) It has been rejected, because it is not massive enough. 
C) It has been rejected, because it cannot "clump" to form the dark matter halo of our galaxy. 
D) It has been rejected, because it has been found to be an unstable particle.

Question 10

Most stars in the galactic halo are:

Accepted Answer

A) Population II stars in globular clusters. 
B) Population II stars not in globular clusters. 
C) Population I stars in open clusters. 
D) Population I stars not in open clusters. 
A) Population II stars in globular clusters. 
B) Population II stars not in globular clusters. 
C) Population I stars in open clusters. 
D) Population I stars not in open clusters.

Question 11

According to the density-wave theory of spiral structure in galaxies:

Accepted Answer

A) collisions between galaxies create waves like the ripples around a rock dropped into a pond, and these are twisted into a spiral pattern by the galaxy's rotation. 
B) collisions between stars send shock waves propagating through the disk of the galaxy. 
C) star-formation regions propagate through the interstellar medium and get stretched into a spiral structure by differential rotation. 
D) stars and interstellar clouds spend more time in regions of higher density, thus maintaining the higher density of the region. 
A) collisions between galaxies create waves like the ripples around a rock dropped into a pond, and these are twisted into a spiral pattern by the galaxy's rotation. 
B) collisions between stars send shock waves propagating through the disk of the galaxy. 
C) star-formation regions propagate through the interstellar medium and get stretched into a spiral structure by differential rotation. 
D) stars and interstellar clouds spend more time in regions of higher density, thus maintaining the higher density of the region.

Question 12

If the Milky Way Galaxy were rescaled to the size of the continental United States, the average distance between stars would be about:

Accepted Answer

A) 5 cm. 
B) 1 m. 
C) 100 m. 
D) 10 km. 
A) 5 cm. 
B) 1 m. 
C) 100 m. 
D) 10 km.

Question 13

What would be the wavelength of maximum emission of interstellar dust grains at a temperature of 65 K? (See Wien's law, Section 5-4, Universe, 11th ed.)

Accepted Answer

A) 450 μm 
B) 22.5 μm 
C) 45 μm 
D) 2.25 μm 
A) 450 μm 
B) 22.5 μm 
C) 45 μm 
D) 2.25 μm

Question 14

If you want to find the distribution of dust in the Milky Way Galaxy, you should observe in which portion of the spectrum?

Accepted Answer

A) x ray 
B) near infrared 
C) far infrared 
D) radio 
A) x ray 
B) near infrared 
C) far infrared 
D) radio

Question 15

How would the value of the orbital speed of a star on the observable outer edge of the plane of a galaxy change if there were no dark matter?

Accepted Answer

A) It would decrease to zero. 
B) It would decrease, but not to zero. 
C) It would remain unchanged. 
D) It would increase. 
A) It would decrease to zero. 
B) It would decrease, but not to zero. 
C) It would remain unchanged. 
D) It would increase.

Question 16

Which of the following BEST describes of the object at the center of our galaxy?

Accepted Answer

A) 4 million $M_{\odot}$ in a volume the size of our solar system 
B) 5 billion $M_{\odot}$ in a volume smaller then Jupiter's orbit 
C) 20 $M_{\odot}$ in a volume the size of the Sun 
D) several trillion $M_{\odot}$ in a volume 2 ly in diameter 
A) 4 million $M_{\odot}$ in a volume the size of our solar system 
B) 5 billion $M_{\odot}$ in a volume smaller then Jupiter's orbit 
C) 20 $M_{\odot}$ in a volume the size of the Sun 
D) several trillion $M_{\odot}$ in a volume 2 ly in diameter

Question 17

Good tracers of spiral arms in galaxies are:

Accepted Answer

A) red giants, because they are bright, and their long wavelengths can be seen through dust. 
B) O and B stars, because they have short lifetimes and are thus always close to where they were formed. 
C) red dwarfs, because they are the most numerous stars. 
D) neutral hydrogen, because it can be observed via the 21-cm line. 
A) red giants, because they are bright, and their long wavelengths can be seen through dust. 
B) O and B stars, because they have short lifetimes and are thus always close to where they were formed. 
C) red dwarfs, because they are the most numerous stars. 
D) neutral hydrogen, because it can be observed via the 21-cm line.

Question 18

Where is the Sun located in our galaxy? (i.e., What is our address in the universe?)

Accepted Answer

A) in the Centaurus arm, between the galactic center and the Orion arm 
B) in the Sagittarius arm, which is between the Centaurus and Orion arms 
C) in or close to the Orion arm, which is between the Sagittarius and Perseus arms 
D) in the Perseus arm, between the Orion and Cygnus arms 
A) in the Centaurus arm, between the galactic center and the Orion arm 
B) in the Sagittarius arm, which is between the Centaurus and Orion arms 
C) in or close to the Orion arm, which is between the Sagittarius and Perseus arms 
D) in the Perseus arm, between the Orion and Cygnus arms

Question 19

The star S2 orbits Sagittarius A* with a period of 15.2 years and a semi-major axis of 950 au. What does Kepler's third law suggest as the total amount of mass inside the orbital radius of S2?

Accepted Answer

A) 1.3 × 106 $M_{\odot}$ 
B) 2.6 × 106 $M_{\odot}$ 
C) 4.1 × 106 $M_{\odot}$ 
D) 9.4 × 109 $M_{\odot}$ 
A) 1.3 × 106 $M_{\odot}$ 
B) 2.6 × 106 $M_{\odot}$ 
C) 4.1 × 106 $M_{\odot}$ 
D) 9.4 × 109 $M_{\odot}$

Question 20

A map of our galaxy deduced from radio observations of the 21-cm line emission from cool hydrogen gas reveals:

Accepted Answer

A) two spiral arms, one on each side of the galaxy. 
B) two spiral arms, which wrap around the galaxy several times. 
C) a smooth distribution of stars, characteristic of an elliptical galaxy. 
D) at least four spiral arms and several short arm segments. 
A) two spiral arms, one on each side of the galaxy. 
B) two spiral arms, which wrap around the galaxy several times. 
C) a smooth distribution of stars, characteristic of an elliptical galaxy. 
D) at least four spiral arms and several short arm segments.

Exam 22: Our Galaxy

Suppose it is discovered that the earliest galaxies were flocculent spirals. What implications might this have?

High-velocity stars are isolated stars that swing in and out of the plane of the galaxy at relatively high velocities with respect to the solar system. Where would you expect to find them?

Harlow Shapley determined the position of the Sun in the galaxy by measuring the distances to 93 globular clusters of stars. How did Shapley obtain the distances to these very distant clusters?

If you want to find the distribution of stars in the Milky Way Galaxy, you should observe in which portion of the spectrum?

Because the rotation curve for the Milky Way Galaxy is approximately flat, a star in a circular orbit 13 kpc from the galactic center has the same orbital speed as the Sun, namely 220 km/sec. How much mass is interior to this star's orbit (in solar masses)?

Which physical process is thought to have created the Local Bubble near our Sun in the galaxy?

A Cepheid variable star is seen to vary regularly with a period of 25 days. How many times more luminous than the Sun would this star appear to be if it were to replace the Sun in our solar system? (See Figure 22-4 of Universe, 11th ed.) ​

Gamma-ray "bubbles" have been found above and below the plane of our galaxy. (See Figure 22-30 of Universe, 11th ed.) These are: ​

The neutrino has been proposed as a dark matter candidate. What is the current status of this idea?

Most stars in the galactic halo are:

According to the density-wave theory of spiral structure in galaxies:

If the Milky Way Galaxy were rescaled to the size of the continental United States, the average distance between stars would be about:

What would be the wavelength of maximum emission of interstellar dust grains at a temperature of 65 K? (See Wien's law, Section 5-4, Universe, 11th ed.)

If you want to find the distribution of dust in the Milky Way Galaxy, you should observe in which portion of the spectrum?

How would the value of the orbital speed of a star on the observable outer edge of the plane of a galaxy change if there were no dark matter?

Which of the following BEST describes of the object at the center of our galaxy?

Good tracers of spiral arms in galaxies are:

Where is the Sun located in our galaxy? (i.e., What is our address in the universe?)

The star S2 orbits Sagittarius A* with a period of 15.2 years and a semi-major axis of 950 au. What does Kepler's third law suggest as the total amount of mass inside the orbital radius of S2?

A map of our galaxy deduced from radio observations of the 21-cm line emission from cool hydrogen gas reveals:

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 Nature of the Stars

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

Galaxies

Quasars and Active Galaxies

Cosmology: The Origin and Evolution of the Universe

Exploring the Early Universe

The Search for Extraterrestrial Life

Filters

A Cepheid variable star is seen to vary regularly with a period of 25 days. How many times more luminous than the Sun would this star appear to be if it were to replace the Sun in our solar system? (See Figure 22-4 of Universe, 11th ed.)

Gamma-ray "bubbles" have been found above and below the plane of our galaxy. (See Figure 22-30 of Universe, 11th ed.) These are: