Deck 10: Galaxies

Question 1

What type of galaxies do astronomers believe are the most common?

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

Answer 1

elliptical

Question 2

What property of a galaxy do you need to measure before you can determine its size?

A) colour
B) mass
C) shape
D) distance

Answer 2

distance

Question 3

What kind of galaxy is the Milky Way?

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

Answer 3

barred spiral

Question 4

You have measured the angular diameter of a galaxy. What information do you need to determine its actual diameter?

A) its mass
B) its age
C) its stellar classification
D) its distance

Question 5

Which of the following is the best example of a selection effect?

A) Globular clusters are not included in catalogues of galaxies.
B) The nearest quasars are not included in quasar catalogues.
C) Bright spiral galaxies are not included in catalogues of nearby galaxies.
D) Dwarf elliptical galaxies are not included in catalogues of nearby galaxies.

Question 6

What kind of galaxies contain large clouds of gas and dust, and both young and old stars, but have no obvious spiral arms or nucleus?

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

Question 7

What factor below is the most important when trying to classify a galaxy as spiral or elliptical?

A) the amount of dust and gas in the galaxy
B) the galaxy's location
C) the number of satellite galaxies
D) the mass of the galaxy

Question 8

Why are spiral galaxies overrepresented compared to elliptical galaxies in some surveys?

A) Spiral galaxies have more active star formation.
B) Spiral galaxies are larger than the largest elliptical galaxies.
C) Spiral galaxies tend to be closer to the Milky Way Galaxy than elliptical galaxies.
D) Spiral galaxies tend to have more luminous red giants than elliptical galaxies.

Question 9

What does an elliptical galaxy contain?

A) mostly lower main-sequence stars and giants
B) mostly upper main-sequence stars
C) mostly upper main-sequence stars and gas and dust
D) roughly equal numbers of upper and lower main-sequence stars

Question 10

Which type of galaxy has a disk and bulge but very little star formation?

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

Question 11

What does an irregular galaxy contain?

A) mostly lower main-sequence stars and giants
B) mostly upper main-sequence stars and giants
C) mostly upper main-sequence stars and gas and dust
D) upper and lower main-sequence stars and gas and dust

Question 12

If modern telescopes were used to take pictures of the entire sky, roughly how many galaxies would those pictures contain?

A) 2 million
B) 20 million
C) 200 billion
D) 2 trillion

Question 13

How do E4 galaxies compare to E7 galaxies?

A) E4 galaxies are younger than E7 galaxies.
B) E4 galaxies are smaller than E7 galaxies.
C) E4 galaxies are rounder than E7 galaxies.
D) E4 galaxies are less massive than E7 galaxies.

Question 14

Which of the following is a nearby irregular galaxy that is interacting with the Milky Way galaxy?

A) the Andromeda Galaxy
B) the Small Magellanic Cloud
C) M87
D) the Whirlpool Galaxy

Question 15

What type of galaxy has an elongated nucleus with a spiral structure extending from the ends of the elongations?

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

Question 16

Which of the following types of galaxies are frequently found in large clusters?

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

Question 17

What is the primary factor used in determining the classification for an elliptical galaxy?

A) size
B) shape
C) mass
D) colour

Question 18

Which of the following statements about galaxies is correct?

A) Most galaxies in the universe are about the same size as the Milky Way.
B) Galaxies come in a wide variety of sizes and shapes, but are all very blue in colour.
C) Small galaxies outnumber large galaxies.
D) Galaxies come in a wide variety of sizes and shapes, but are all very red in colour.

Question 19

How is a lenticular galaxy different from a normal spiral galaxy?

A) It has less active star formation.
B) It has more spiral arms.
C) It is more spherical in shape.
D) It is more chaotic and irregular.

Question 20

What does a spiral (S or SB) galaxy contain?

A) mostly lower main-sequence stars and giants
B) upper and lower main-sequence stars, gas and dust
C) mostly upper main-sequence stars, gas and dust
D) mostly upper main-sequence stars

Question 21

What is a megaparsec equivalent to?

A) 3.26 light years
B) 206,265 AU
C) 1000 parsecs
D) 3.26 million light years

Question 22

Which of the following lists the steps in the astronomical distance ladder in order of the smallest to largest distances they can reach?

A) Cepheid variables, parallax, Tully Fisher relationship
B) parallax, Tully Fisher relationship, Cepheid variables
C) parallax, Cepheid variables, Tully Fisher relationship
D) Cepheid variables, Tully Fisher relationship, parallax

Question 23

If a galaxy has an apparent recession velocity of 8000 km/sec and the Hubble constant is approximately 70 km/sec/Mpc, what is the distance to this galaxy?

A) 8.75 × 10^-3 Mpc
B) 114 Mpc
C) 8.75 × 10³ Mpc
D) 2.4 × 10⁹ Mpc

Question 24

What distance method is used to determine the distance to the most distant galaxies?

A) radar echo
B) supernova observations
C) the period-luminosity relationship of variable stars
D) parallax

Question 25

If you wanted to measure the distance to a galaxy, what kind of objects within it could you observe?

A) Cepheid variable stars
B) Herbig-Haro objects
C) large globular clusters
D) dust lanes

Question 26

Why do more distant galaxies have higher redshifts?

A) They have had more time to move since their formation.
B) The gravitational field is stronger at large distances causing a gravitational redshift.
C) Space has expanded by a greater amount between us and more distant galaxies.
D) The galaxies that moved the fastest after the big bang have travelled the farthest.

Question 27

What is the Hubble constant essentially a measure of?

A) the number of galaxies in the universe
B) the expansion rate of the universe
C) the age of the Milky Way galaxy
D) the amount of dark matter in an average galaxy

Question 28

Which of the following lists objects in order of increasing look-back time as observed from Earth?

A) the Sun, the Moon, SagA*, Andromeda Galaxy
B) Andromeda Galaxy, SagA*, the Sun, the Moon
C) the Moon, the Sun, SagA*, Andromeda Galaxy
D) the Moon, the Sun, Andromeda Galaxy, SagA*

Question 29

Edwin Hubble measured the distance to the Andromeda Galaxy. How did he do that?

A) He applied the period-luminosity relation to Cepheids.
B) He measured the parallax of the Andromeda Galaxy.
C) He estimated the number of galaxies in the universe.
D) He applied the white dwarf brightness relation.

Question 30

The Hubble constant is approximately 70 km/sec/Mpc. Roughly how far away is a galaxy with an apparent recession velocity of 2100 km/sec?

A) 30 Mpc
B) 2030 Mpc
C) 2170 Mpc
D) 147 000 Mpc

Question 31

The Tully Fisher relationship relates a galaxy's luminosity to which other quantity?

A) mass
B) rotation rate
C) pulsation period
D) colour

Question 32

How would you use the Hubble Law to measure the distance to a galaxy?

A) Measure its apparent recession velocity and divide by the age of the universe.
B) Measure its Cepheid variables and multiply by the Hubble constant.
C) Measure its apparent recession velocity and divide by the Hubble constant.
D) Measure its apparent recession velocity and add it to the Hubble constant.

Question 33

You measure the rotation rate and apparent brightness of a spiral galaxy. What should you use to determine its distance?

A) its angular diameter
B) the Hubble law
C) the Tully Fisher relationship
D) the period-luminosity relation

Question 34

What is look-back time?

A) the time it takes for the light from an object to reach Earth
B) the time it takes for a distant object to form
C) the time it takes for an object to orbit once around the Milky Way
D) the age of an object in light-years

Question 35

The Hubble constant is approximately 70 km/sec/Mpc. Roughly how far away is a galaxy with an apparent recession velocity of 7000 km/sec?

A) 10 Mpc
B) 70 Mpc
C) 100 Mpc
D) 700 Mpc

Question 36

What distance method is used to calibrate galaxy distances?

A) parallax
B) radar measurements
C) variable stars
D) the moving cluster method

Question 37

The Hubble law describes a relationship between two characteristics of a galaxy. What are they?

A) mass and luminosity
B) distance and luminosity
C) mass and recession velocity
D) distance and recession velocity

Question 38

Which of the following objects can be used as a standard candle?

A) Cepheid variables
B) spiral galaxies
C) type II supernovae
D) quasars

Question 39

If Galaxy A is found to have a recessional velocity four times greater than that of Galaxy B, what can you say about their relative distances from Earth?

A) Galaxy A is one quarter as far away as Galaxy B.
B) Galaxy A is half as far away as Galaxy B.
C) Galaxy A is twice as far away as Galaxy B.
D) Galaxy A is four times as far away as Galaxy B.

Question 40

You observe a Cepheid variable star in a nearby galaxy. How would you determine its distance?

A) apply the peak colour-magnitude relation
B) apply the period-luminosity relation
C) apply the Hubble Law
D) measure the parallax

Question 41

Why do astronomers believe that the Milky Way Galaxy has never merged with another large galaxy?

A) it has very few tidal tails
B) it has spiral arms with gas and dust
C) it contains very little dark matter
D) its central bulge has a barred shape

Question 42

Which of the following is the Milky Way Galaxy part of?

A) the Virgo cluster
B) the Large Magellanic Cloud
C) the Small Magellanic Cloud
D) the Local Group

Question 43

What information about a cluster of galaxies can lensing of background galaxies by the cluster be used to determine?

A) luminosity
B) mass
C) distance
D) diameter

Question 44

Where is most of the mass of a galaxy found?

A) in the massive O and B stars
B) in the H II regions
C) in the dark matter halo
D) in the disk

Question 45

If a disk galaxy is reasonably close and edge-on, the Doppler shift of the galaxy disk material relative to the centre can be measured at several distances from the galaxy's centre. What does this measurement tell us about the galaxy?

A) the galaxy's luminosity
B) the galaxy's diameter
C) the galaxy's mass
D) the galaxy's velocity dispersion curve

Question 46

Suppose you want to know the distance to a particular galaxy. What's the biggest problem with using type Ia supernovae to measure the distance?

A) Supernovae are extremely luminous and can outshine their galaxies.
B) Supernovae all have about the same luminosity.
C) Because supernovae are very energetic, they are not well understood.
D) Supernovae are rare, so you might have to wait a long time.

Question 47

Which of the following best describes starburst galaxies?

A) They contain a large number of very young stars, but very little evidence of gas clouds.
B) They contain a large number of very old stars and almost no gas or dust.
C) They are often associated with galaxy collisions.
D) They are commonly found in rich clusters.

Question 48

A certain spiral galaxy has approximately 100 billion solar masses of stars, gas, and dust. Which of the following is likely to be closest to the mass of dark matter it contains?

A) 100 billion solar masses
B) 200 billion solar masses
C) 1 trillion solar masses
D) 100 trillion solar masses

Question 49

Which of the following are produced when two galaxies pass near each other and pull large streamers of stars, gas, and dust away from each other?

A) ring galaxies
B) rotation curves
C) tidal tails
D) irregular galaxies

Question 50

Observations of galaxies and clusters of galaxies indicate that a percentage of the matter in the universe is dark matter. Which of the following is closest to that percentage?

A) 5%
B) 25%
C) 35%
D) 85%

Question 51

How might the mass of a disk galaxy be found?

A) by the double galaxy method
B) by the rotation curve method
C) by the cluster method
D) by the main-sequence fitting method

Question 52

Which of the following describes part of the evolution of an elliptical galaxy?

A) It will turn into an irregular galaxy when it has used up all of its gas and dust.
B) It may result from the collision and merger of spiral galaxies.
C) It evolves from a single spiral galaxy when the spiral has used up all of its gas and dust.
D) It would become a starburst galaxy if it were to move through the hot intergalactic medium of a cluster.

Question 53

Which of the following types of objects is the Milky Way part of?

A) a rich cluster
B) a poor cluster
C) the Virgo cluster
D) a globular cluster

Question 54

Which of the following best describes poor galaxy clusters?

A) They contain lots of young stars and are found in the disk of a spiral galaxy.
B) They contain more than 1000 galaxies and are generally elliptical in shape.
C) They contain fewer than 1000 galaxies and have irregular shapes.
D) They are found in the nucleus of the galaxy.

Question 55

What can the rotation curve of a galaxy be used to determine?

A) the mass of the galaxy
B) the radius of the galaxy
C) the luminosity of the galaxy
D) the relative amount of gas and dust in the galaxy

Question 56

Why do we expect galaxies to collide fairly often?

A) Galaxy separation distances are not that large compared to their sizes.
B) Galaxies contain large amounts of neutral hydrogen.
C) Galaxies' large masses cause gravitational attraction.
D) Galaxies are moving quickly toward each other.

Question 57

When does gravitational lensing occur?

A) when light passes near a massive object and is deflected by the object's gravitational field
B) when a galaxy has a central black hole with an accretion disk
C) when the mass of a galaxy is greater than expected from the luminosity of the galaxy
D) when the mass of a galaxy is less than expected from the luminosity of the galaxy

Question 58

Where was gravitational lensing first observed?

A) near the Sun during an eclipse
B) in galaxy clusters
C) in a prism held by Newton
D) in quasars

Question 59

Which of the following generally contain well over 1000 galaxies (mainly ellipticals) packed closely together?

A) local groups
B) poor clusters
C) rich clusters
D) tidal tails

Question 60

What would happen to stars near the outer edge of a galaxy if all of the dark matter could be instantly removed?

A) they would continue on their current orbits
B) they would spiral inwards toward the centre
C) they would be ejected from the galaxy
D) they would cease fusing elements in their core

Question 61

How does the unified model describe an active galactic nucleus?

A) as a supermassive black hole at the centre of a normal spiral galaxy
B) as a supermassive black hole surrounded by an accretion disk and a dense disk of gas
C) as an accretion disk around a neutron star
D) as a gravitationally lensed high-redshift galaxy

Question 62

According to the unified model of active galactic nuclei, what is observed if our line of sight is parallel to the plane of the dense disk of an active galactic nucleus?

A) no spectral emission lines
B) broad spectral lines
C) narrow spectral lines
D) a thin accretion disk

Question 63

Which of the following emits large amounts of energy, but photographically appears to be a single point of light, much like a star?

A) an elliptical galaxy
B) a spiral galaxy
C) a quasar
D) a double-lobed radio source

Question 64

What of the following could be referred to as "galactic cannibalism" ?

A) the collapse of a giant cloud to form a galaxy
B) the merging of galaxies
C) galaxies drawing in gas from the intergalactic medium
D) the destruction of a galaxy's globular clusters by the galaxy's nucleus

Question 65

In the unified model of active galactic nuclei, what is the broad line region in an active galactic nucleus?

A) It is composed of clouds of gas and stars moving at very high orbital velocities near a supermassive black hole.
B) It is composed of a super massive black hole surrounded by empty space.
C) It is the region responsible for producing the bright continuous radiation from within the event horizon.
D) It is the region responsible for the narrow absorption lines seen in Type 2 Seyfert galaxies.

Question 66

What inflates the lobes of radio emission in a radio galaxy?

A) jets of excited gas flowing from the central galaxy
B) jets of high-energy sound waves flowing from the central galaxy
C) a disk of ionized material that orbits very near a supermassive black hole
D) dark clouds of very cold gas and dust

Question 67

Why were quasars so mysterious when first discovered?

A) Quasars emitted radio energy like radio galaxies, but looked like stars in visible light.
B) Quasars showed significant gravitational lens effects.
C) The spectra of quasars looked like those of M dwarfs.
D) The large redshifts originally indicated that they were orbiting the centre of the Milky Way.

Question 68

If the redshifts of quasars arise from the expansion of the universe, yet they have brighter magnitudes than galaxies with the same redshifts, what must be generally true of quasars?

A) They are very small.
B) They are within the Local Group.
C) They are moving toward Earth with a large radial velocity.
D) They emit a very large amount of energy per second.

Question 69

The hydrogen Balmer line Hβ has a wavelength of 486.1 nanometres in the laboratory. The same line is observed in a quasar at 2430.5 nm. What is the quasar's redshift?

A) 0.8
B) 1.25
C) 4
D) 5

Question 70

Mathematical models indicate that one type of galaxy is produced by high-speed collisions in which a smaller galaxy passes through a larger galaxy almost perpendicular to the disk of the larger galaxy. What is this type of galaxy called?

A) ring
B) spiral
C) antenna
D) irregular

Question 71

Why are supermassive black holes believed to be located at the centre of many galaxies?

A) because the rotation curve of the galaxy indicates that 90% of the galaxy is dark matter
B) because the orbital motion of material near the centre is very fast and indicates a very massive core
C) because the shape of the bulge in all spiral galaxies can be supported only by a supermassive black hole
D) because the spiral structure requires a black hole to maintain the spiral arms

Question 72

Which of the following is a feature of Seyfert galaxies?

A) They are more common in isolated galaxies than in close pairs of galaxies.
B) They have spectra which show that gas in their cores is hot and moving quickly.
C) They generally show redshifts greater than 6.
D) They are elliptical and are among the largest galaxies.

Question 73

Which of the following indicates that quasars must be small?

A) They have high radial velocities.
B) They are surrounded by quasar fuzz.
C) They radiate huge amounts of energy.
D) They fluctuate rapidly on time scales as short as a few hours.

Question 74

What would happen to the Sun if the supermassive black hole in the centre of our galaxy could be instantly removed?

A) It would spiral in toward the centre of the galaxy.
B) It would remain on its current orbit.
C) It would move to a larger orbit.
D) It would be ejected from our galaxy.

Question 75

What kind of radiation is produced by the radio lobes that are on each side of some radio galaxies, and also by the jets from them?

A) mainly 21-cm radiation
B) mainly synchrotron radiation
C) mainly black body radiation
D) mainly emission lines due to hydrogen

Question 76

Which type of active galaxy can be seen at the greatest distance?

A) Seyfert galaxies
B) radio galaxies
C) quasars
D) BL Lac objects

Question 77

What is the major observational difference between a Seyfert galaxy and a normal spiral galaxy?

A) Normal spiral galaxies usually have shorter spiral arms.
B) Normal spiral galaxies never contain a supermassive black hole at their centre.
C) The central region of a Seyfert galaxy is much brighter.
D) Seyfert galaxies don't contain any star formation.

Question 78

Which of the following describes the way that ring galaxies are believed to form?

A) when two spiral galaxies collide, along a direction parallel to one galaxy's disk
B) when two galaxies of different sizes collide along a direction perpendicular to the larger galaxy's disk
C) when two elliptical galaxies collide at a position offset from their centres
D) when more than two galaxies collide at the same time, along a straight line

Question 79

What produces the energy from an active galactic nucleus?

A) the collision of two spiral galaxies
B) matter flowing out of a central star-forming region
C) the collision of two radio jets
D) matter flowing into a supermassive black hole

Question 80

Which of the following are spiral galaxies that have small luminous nuclei?

A) active
B) radio
C) Seyfert
D) blazar