Deck 16: A Universe of Galaxies

Question 1

Which galactic phenomenon is triggered by the same process as spiral structure?

A) galactic bars
B) globular clusters
C) tidal streams
D) the formation of spirals from ellipticals

Answer 1

galactic bars

Question 2

Edwin Hubble believed that:

A) galaxies evolve from ellipticals to spirals.
B) spiral nebulae are part of the Milky Way.
C) elliptical galaxies are always more distant than spiral galaxies.
D) lenticular galaxies are the endpoint of galactic evolution.

Answer 2

galaxies evolve from ellipticals to spirals.

Question 3

In the early 20th century,some astronomers incorrectly believed that they could observe features in spiral nebulae rotate over the course of a few years.If those observations were correct,what would they have immediately suggested about the nature of these nebulae?

A) that they were island universes
B) that they were inside the Milky Way
C) that they were forming stars
D) that they were accretion disks

Answer 3

that they were inside the Milky Way

Question 4

Edwin Hubble classified elliptical galaxies according to their:

A) size.
B) color.
C) apparent shape.
D) velocities.

Question 5

What was the subject of the "Great Debate" in astronomy?

A) the truth of the geocentric and heliocentric theories
B) the age of the Universe
C) the nature of spiral nebulae
D) the truth of the Big Bang model

Question 6

Which astronomer definitively established the existence of galaxies outside the Milky Way?

A) Galileo
B) William Herschel
C) Harlow Shapley
D) Edwin Hubble

Question 7

Because of an obscuring atmosphere,an observer in a distant galaxy can only see the nearest 1,000 stars to his or her home planet.How could the observer most directly determine that he or she lives inside an elliptical galaxy?

A) by measuring the brightnesses of the stars
B) by mapping the locations of the stars on the sky
C) by measuring the differences in velocities between the stars
D) by measuring the masses of the stars

Question 8

A galaxy with a total mass of 10⁶ M_Sun is most likely to be:

A) a spiral.
B) a barred spiral.
C) a dwarf elliptical.
D) a lenticular.

Question 9

The figure below shows a schematic of the Hubble tuning-fork diagram.At which labeled point will a lenticular galaxy be placed?

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

Question 10

How do stars move inside of ellipticals?

A) They move along random orbits.
B) They all circulate in the same direction with little variation.
C) They all circulate in the same direction, but with some variation in velocities.
D) They move on mostly vertical orbits.

Question 11

A galaxy appears cigar-shaped on the sky.It has a population of globular clusters and predominantly old stars.It is most likely a(n):

A) spiral.
B) barred spiral.
C) elliptical.
D) irregular.

Question 12

A low-mass galaxy is situated 10 kiloparsecs from a flocculent spiral galaxy.Which of the following is most likely to describe the low-mass galaxy?

A) irregular
B) spiral
C) barred spiral
D) elliptical

Question 13

An observer detects a galaxy with a blue color,lots of 21-cm emission,and a moderate total mass.It is most likely a(n):

A) irregular.
B) elliptical.
C) lenticular.
D) spiral.

Question 14

What is "spectroscopic parallax"?

A) using stellar spectra to measure distances
B) using the apparent angular motion of stars to measure distances
C) using the redshifts of galaxy absorption lines to measure distances
D) using the apparent angular motion of galaxies to measure distances

Question 15

In a barred spiral galaxy,the spiral:

A) structure is always very obvious.
B) arms extend from the ends of the bar.
C) structure gradually destroys the bar.
D) arms are more tightly wound than in spiral galaxies without bars.

Question 16

In the context of the cosmic distance ladder,to what does calibration refer?

A) measuring Hubble's constant
B) tuning one distance determination method to another
C) measuring the distance to Cepheid variable stars
D) defining units

Question 17

The figure below shows a schematic of the Hubble tuning-fork diagram.At which labeled point might a spiral galaxy with a very small bulge lie?

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

Question 18

An elliptical galaxy has:

A) blue stars and plunging orbits.
B) red stars and lots of gas and dust.
C) red stars and plunging orbits.
D) blue stars and lots of gas and dust.

Question 19

A spiral galaxy is observed to have undergone a recent episode of intense star formation near its center.Which of the following is this galaxy most likely to have had in its recent past?

A) a flocculent phase
B) a grand design phase
C) globular clusters
D) a bar

Question 20

As a result of collisions,galaxies are most likely to evolve from:

A) ellipticals to spirals.
B) spirals to ellipticals.
C) ellipticals to irregulars.
D) irregulars to ellipticals.

Question 21

An astronomer discovers a bright,steady source of high-energy gamma rays at the center of a galaxy.What is the most likely explanation for this source?

A) rapid star formation
B) a gamma-ray burst
C) fast-moving gas clouds orbiting a black hole
D) Type Ia supernova

Question 22

What does the M-sigma relation demonstrate about black holes?

A) They result from massive stars' deaths.
B) That black holes and galaxies grow together.
C) They grow primarily through accretion.
D) That black holes form the majority of mass within galactic bulges.

Question 23

Which type of astronomical object is shown in the figure below?

A) Seyfert galaxy
B) irregular galaxy
C) quasar
D) radio galaxy

Question 24

Which of the following is NOT a component of the unified model of active galactic nuclei?

A) a corona
B) a jet
C) a torus
D) an accretion disk

Question 25

An extragalactic source with a compact size and strong,broad emission lines is also likely to have:

A) variable emission.
B) low redshift.
C) strong radio absorption.
D) a stellar spectrum.

Question 26

Galaxy A is located at the North Celestial Pole,while galaxy B is located at the South Celestial Pole.Galaxy A is 100 Mpc from Earth,while galaxy B is 500 Mpc from Earth.What is the relative velocity between them,as observed from Earth?

A) 2.8 x 10⁴ km/s
B) 4.2 x 10⁴ km/s
C) 9.0 x 10³ km/s
D) 3.5 x 10⁴ km/s

Question 27

What property of a Type Ia supernova must be measured in order to use it as a standard candle?

A) luminosity
B) light curve
C) color
D) redshift

Question 28

What fraction of galaxies have black holes at their centers?

A) 0.1 percent
B) 1 percent
C) 10 percent
D) 100 percent

Question 29

Which of the following accurately characterizes emission lines from active galactic nuclei?

A) Active galaxies always have strong emission lines.
B) Some active galaxies have strong emission lines, but others have no emission lines.
C) Active galaxies never have strong emission lines.
D) Emission lines cannot be observed from active galaxies because of their extreme luminosities.

Question 30

Which of the following lists astronomical distance measurement techniques in order of the maximum distance to which they are useful?

A) parallax, spectroscopic parallax, Hubble's law, Type Ia supernova
B) parallax, Cepheid variables, spectroscopic parallax, Hubble's law
C) parallax, Cepheid variables, Type Ia supernova, the Tully-Fisher law, Hubble's law
D) parallax, Cepheid variables, Type Ia supernova, Hubble's law

Question 31

Why is rapid variability (over the course of weeks)a strong argument that quasars are powered by supermassive black holes?

A) Variability shows that black holes grow rapidly.
B) Variability shows that black holes are unstable.
C) Variability allows astronomers to estimate the size of the emitting region.
D) Variability rules out accretion disks as the source.

Question 32

Which of the following is necessary to measure the distance to a galaxy with Hubble's law?

A) the Doppler effect formula
B) resolving a Cepheid variable in the galaxy
C) the size of the solar system
D) the rotation velocity of the galaxy

Question 33

Suppose astronomers discover an error in the size of the astronomical unit.How would this affect distances measured with Hubble's law?

A) It would not affect such measurements, because they use galaxy redshifts.
B) It would not affect such measurements, because calibration protects against such errors.
C) Measurements with Hubble's law would change because of the change to inferred galaxy redshifts.
D) Measurements with Hubble's law would change because of the calibration process.

Question 34

An astronomer discovers a knot of emission that appears to escape a radio galaxy at three times the speed of light.What makes this phenomenon possible?

A) The central black hole produces an exotic particle that travels faster than the speed of light.
B) Magnetic fields accelerate the jet particles.
C) Nothing; it is an optical illusion.
D) Nothing; it is a consequence of the cosmological expansion.

Question 35

The figure below shows a schematic diagram of an active galactic nucleus (AGN).How might an observer lying along the direction indicated by the arrow describe this AGN?

A) blazar
B) radio-loud galaxy
C) radio-quiet galaxy
D) quasar

Question 36

Why are the jets from radio galaxies compelling evidence that black holes power active galactic nuclei?

A) their extreme luminosity
B) their relativistic speed
C) their compact bases
D) all of the above

Question 37

An astronomer discovers an extremely luminous galaxy with broad emission lines that have very large redshifts.This is most likely a:

A) Seyfert galaxy.
B) barred spiral galaxy.
C) spiral galaxy.
D) quasar.

Question 38

The figure below is an illustration of what astronomical relation?

A) Wien's law
B) the Tully-Fisher relation
C) Hubble's law
D) the inverse-square law

Question 39

Which of the following properties are NOT typical of active galactic nuclei?

A) strong absorption lines
B) strong emission lines
C) strong radio emission
D) compact size

Question 40

An astronomer measures a galaxy to have an apparent recession velocity of 2,100 km/s.How far away is the galaxy?

A) 300 Mpc
B) 30 Mpc
C) 300 kpc
D) 1.4 x 10⁵ Mpc

Question 41

An astronomer discovers an unusual active galactic nucleus without any orbiting clouds.How would such a source differ from a typical quasar?

A) It would lack emission lines.
B) It would lack a jet.
C) It would not have variability.
D) all of the above

Question 42

A bright source doubles its luminosity over the course of a week.How large is the source?

A) 12 AU
B) 1200 AU
C) 0.12 parsecs
D) 1.2 parsecs

Question 43

Which astronomer discovered dark matter in spiral galaxies?

A) Harlow Shapley
B) Edwin Hubble
C) Arno Penzias
D) Vera Rubin

Question 44

What type of galaxy is shown in the image below?

Question 45

Why was the large size of Edwin Hubble's telescope essential for resolving the nature of spiral nebulae?

Question 46

Which cosmic distance measurement techniques rely on the observation of standard candles?

Question 47

What are the four major classes of galaxies in the Universe?

Question 48

The figure below shows the rotation curves of several spiral galaxies,extending to the very edge of their visible disks.What do these curves tell us about the distribution of dark matter in these galaxies?

A) Most of the dark matter is in clumps.
B) Most of the dark matter is in the bulge.
C) Most of the dark matter is near stars.
D) Most of the dark matter is in the galaxies' outskirts.

Question 49

A black hole with a mass of 10⁹ MSᵤn brightens rapidly and increases its luminosity by a factor of two.Approximately how long would it take for an observer on Earth to see the black hole reach its maximum brightness?

A) 3 minutes
B) 3 hours
C) 3 days
D) 3 weeks

Question 50

The mass of a supermassive black hole within the galaxy will most accurately predict the:

A) total mass of the galaxy.
B) mass of the galaxy's stellar halo.
C) mass of the galaxy's bulge.
D) mass of the galaxy's gas clouds.

Question 51

Name three aspects of elliptical galaxies that point toward their origin in collisions between galaxies.

Question 52

Why were Cepheid variables essential to the discovery of galaxies outside the Milky Way?

Question 53

Which of the following quantities is most useful to astronomers when measuring the dark matter content of galaxies?

A) color
B) age
C) stellar velocities
D) luminosity

Question 54

Two elliptical galaxies have identical radii and luminosities,but stars in galaxy A have a maximum orbital speed three times that of galaxy B.How much more massive is galaxy A than galaxy B?

A) nine times more
B) three times more
C) 1.7 times more
D) 1.3 times more

Question 55

Why is it important for astronomers to find galaxies with Type Ia supernova and Cepheid variables?

Question 56

The figure below shows a schematic diagram of an active galactic nucleus.Which region is responsible for broad emission lines?

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

Question 57

How do astronomers most directly measure the amount of dark matter in elliptical galaxies?

A) through their rotation curves
B) through their velocity dispersion
C) through their radii
D) through their reddening

Question 58

Why are the bars in barred spiral galaxies typically bright?

Question 59

The figure below shows three spiral galaxies.Classify them as Sa,Sb,and Sc galaxies.There is one of each type of galaxy in the figure.

Question 60

Contrast spiral and elliptical galaxies in terms of their color,gas content,and orbital properties.

Question 61

Astronomers discover a galaxy 1.4 Gpc from Earth.What is its velocity relative to Earth,and in which direction does it point?

Question 62

How can the velocity dispersion and radius of an elliptical galaxy determine its mass?

Question 63

An astronomer discovers a highly luminous,compact emission source in the center of a distant galaxy.What is the most likely power source for this emission?

Question 64

What two observables of a galaxy correlate most strongly with the mass of the galaxy's supermassive black hole?

Question 65

An astronomer discovers a galaxy with unusually broad emission lines.What is the most likely source of these lines?

Question 66

An astronomer measures the rotation speed of a spiral galaxy.How can she use this to estimate the galaxy's distance?

Question 67

What is the most important factor determining the type of AGN an observer sees for any particular source?

Question 68

The figure below shows the rotation curves of several nearby spiral galaxies.What does the shape of these curves tell us about the content of these galaxies?

Question 69

A galaxy is flanked by a pair of regions of bright radio emission,each 300 kpc across.What is the most likely power source of this emission?