Deck 17: Galaxies

Question 1

What type of galaxy has a mix of young and old stars, an abundant amount of gas and dust, ongoing star formation, and a definitive shape?

A) spiral galaxies
B) elliptical galaxies
C) irregular galaxies
D) All types of galaxies share these features

Answer 1

spiral galaxies

Question 2

What type of galaxy has only old stars, little dust, low density, hot gas, and no star formation?

A) spiral galaxies
B) elliptical galaxies
C) irregular galaxies
D) All types of galaxies share these features

Answer 2

elliptical galaxies

Question 3

A(n) ___ type galaxy is ____________ with elongated central regions.

A) Sa; a spiral galaxy
B) E0; an elliptical galaxy
C) E7; a spiral galaxy
D) SB; a spiral galaxy

Answer 3

SB; a spiral galaxy

Question 4

_____ galaxies contain mostly Population II stars; while _____ galaxies contain both Population I and Population II stars.

A) Irregular; elliptical
B) Elliptical; spiral
C) Irregular; spiral
D) Spiral; elliptical

Question 5

____ galaxies have smaller nuclei and loosely wound arms compared to ____ galaxies.

A) Sd; Sc
B) Sa; Sb
C) Sa; S0
D) E0; S0

Question 6

The accurate determination of star distances by the method of standard candles requires accurate knowledge of the _____ of the standard candle.

A) speed
B) luminosity
C) temperature
D) size

Question 7

Hubble's law implies that the _____ galaxies have larger _____ in their spectral lines.

A) more distant; redshift
B) more distant; blueshift
C) nearby; blueshift
D) nearby; redshift

Question 8

Hubble's law is not applicable to ___________ because the motion of these galaxies is affected by ______________.

A) elliptical galaxies; their rotation
B) spiral galaxies; their spiral arms
C) distant galaxies; intervening dust
D) galaxies in the Local Group; gravitational interaction with the Milky Way

Question 9

_______ galaxies may contain a few million to few trillion solar masses.

A) Spiral
B) Elliptical
C) Irregular
D) Independent of their type

Question 10

Of the methods listed below, which is the best for measuring the distance to the Andromeda galaxy, a member of the Local Group?

A) the Cepheid variable period-luminosity relationship
B) Hubble's law
C) trigonometric parallax

Question 11

The ________ that is affecting the motion of the Local Group is believed to be a yet unseen ____________.

A) Great Wall; super massive black hole
B) Great Wall; Great Attractor
C) Great Attractor; super massive black hole
D) Great Attractor; cluster of superclusters

Question 12

You measure Cepheid variables in galaxy A and galaxy B. Both Cepheids have the same period, but the one in galaxy B appears 16 times brighter than the other. You conclude

A) Galaxy B is 4 times more distant than galaxy A.
B) Galaxy B is 16 times more distant than galaxy A.
C) Galaxy B is 16 × 16 = 256 times more distant that galaxy A.
D) Galaxy A is 16 × 16 = 256 times more distant that galaxy B.
E) Galaxy A is 4 times more distant than galaxy B.

Question 13

A large galaxy contains mostly old (Pop II) stars spread smoothly throughout its volume, but it has little dust or gas. What type galaxy is it most likely to be?

A) Irr
B) S
C) SB
D) E
E) All of these choices are correct.

Question 14

Galaxies come in three varieties, which are

A) barred spiral, irregular, and Seyfert.
B) Seyfert, radio, and quasar.
C) spiral, elliptical, and irregular.
D) old, young, and intermediate.

Question 15

Which of the following is not a property of elliptical galaxies?

A) They contain mostly old (Pop II) stars.
B) They have little dust or cold gas.
C) They have prominent spiral arms.
D) Stars are distributed smoothly throughout their volume.

Question 16

The Hubble Law does not work for nearby galaxies because…

A) it is difficult to take the spectrum of nearby galaxies as compared to distant galaxies.
B) the speed of nearby galaxies is affected by their gravitational interaction with one another.
C) nearby galaxies are contracting rather than expanding.
D) the Hubble law works for all galaxies; distance doesn't matter.

Question 17

What approach for estimating the distance to a galaxy requires the measurement of a galaxy's rotation speed?

A) the Tully-Fisher method
B) Cepheid variables as standard candles
C) Hubble's law
D) Type Ia supernova as standard candles

Question 18

A galaxy's spectrum has a redshift of 30,000 kilometers per second. If the Hubble constant is 75 kilometers per second per megaparsec, how far away from Earth is the galaxy?

A) 10⁶ megaparsecs
B) 1,000 megaparsecs
C) 20 megaparsecs
D) 50 megaparsecs
E) 400 megaparsecs

Question 19

A galaxy has a recession velocity of 10,000 km/sec. If the Hubble constant is 65 km/sec. per megaparsec, roughly how far away is the galaxy?

A) 10 megaparsecs
B) 25 megaparsecs
C) 60 megaparsecs
D) 130 megaparsecs

Question 20

A(n) _______ galaxy is the result of the collision and merger of galaxies that leave little cold gas remaining in the system.

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

Question 21

An encounter in which a large galaxy absorbs a smaller galaxy is referred to as

A) "Galactic absorption".
B) "Galactic merger".
C) "Galactic cannibalism".
D) "Galactic assimilation".

Question 22

What is the most likely outcome after the collision between two spiral galaxies?

A) The destruction of most of their stars
B) Enhanced formation of spiral arms
C) Formation of a larger galaxy
D) All of these choices are correct.

Question 23

_____ form when galaxies collide and _____.

A) S0 galaxies; all their stars are destroyed
B) Starburst galaxies; star formation is triggered, making them very bright
C) Quasars; emit large amounts of heat and radio waves
D) Starburst galaxies; all their stars are destroyed

Question 24

What is the most likely outcome after the collision between two spiral galaxies?

A) The destruction of most of their stars
B) Enhanced formation of new stars
C) Formation of a supermassive black hole
D) All of these choices are correct.

Question 25

When two galaxies collide, what happens to their stars?

A) About 30% of them collide and become black holes.
B) About 50% of them become binary stars.
C) The evolution of all the stars in the larger galaxy is accelerated.
D) Nothing happens to them, except that their orbits may change.

Question 26

Why are galaxy collisions of interest?

A) Collisions and mergers play an important role in shaping galaxies.
B) Collisions have a strong effect on the evolution of stars.
C) Collisions are extremely rare.
D) Collisions generate hundreds of black holes.

Question 27

Most of the Seyfert galaxies are __________.

A) elliptical
B) spiral
C) irregular
D) All of these choices are correct.

Question 28

What type of object is believed to be the central source of energy for an active galaxy?

A) an unusually large and bright main sequence star
B) a large amount of gas and dust
C) a massive black hole
D) globular cluster

Question 29

Which of the following are active galaxies?

A) radio galaxies
B) quasars
C) Seyfert galaxies
D) All of these choices are correct.

Question 30

Seyfert galaxies are______________.

A) bright elliptical galaxies
B) small irregular galaxies
C) spiral galaxies whose nucleus is abnormally luminous
D) isolated black holes emitting radio waves
E) None of these choices is correct.

Question 31

Which of the following statements about quasars is notcorrect?

A) Their spectra have the largest redshifts observed.
B) They are probably the most distant observable objects.
C) They have abnormally high luminosities.
D) Their cores are extremely large, probably several thousand light-years across.
E) Sometimes they appear in pairs, due to gravitational lenses formed by intervening galaxies.

Question 32

What observational evidence suggests that the centers of quasars are small, about a fraction of a light-year?

A) the fact that quasars are so distant, and therefore are very young
B) photographs of quasars
C) They emit radiation over a very wide range of wavelengths
D) The intensity of their radiation fluctuates over periods of months
E) All of these choices are correct.

Question 33

What is the origin of synchrotron radiation in radio galaxies?

A) high-speed electrons spiraling around the magnetic field lines
B) supernova explosions
C) neutron stars at the center of the radio galaxy
D) hydrogen gas
E) radiation from a massive black hole at the center of the galaxy

Question 34

What is the origin of the lobes often observed on opposite sides of radio galaxies?

A) gas ejected from the core of the galaxy
B) high-speed electrons spiraling around magnetic field lines
C) hot planetary nebulas surrounding the galaxy
D) black holes orbiting the center
E) supernovae from massive stars

Question 35

Astronomers speculate that most galaxies have a massive black hole at their center. What could be the origin of the suspected black hole?

A) First, a supernova explosion formed a black hole, which in time became more massive by accretion.
B) the collision of galaxies
C) The gravitational attraction drew in stars from the disk.
D) the rapid rotation of the galaxy that compressed material to high densities
E) dark matter at the galactic center

Question 36

What is thought to be at the center of most galaxies?

A) an unusually large and bright main sequence star
B) a globular cluster
C) an open cluster
D) a massive black hole
E) a regularly exploding nova

Question 37

Suppose that an astronomer discovers an active galaxy, and that the intensity of the radiation from the galactic nucleus fluctuates in intervals of 8 minutes. Based on her observations, the astronomer should infer that the active nucleus of this galaxy is about ___ in diameter. (Hint: It takes light about 8 minutes to reach Earth from the Sun.)

A) 1 AU
B) 1 Mpc
C) 8 AU
D) 8 light-years

Question 38

Astronomers believe that the X-ray radiation from the nuclei of active galaxies comes from _____________.

A) a black hole
B) the accretion disk around a massive black hole
C) gravity waves
D) magnetic fields

Question 39

What are some signs of an active galaxy?

A) The core is very bright.
B) The core is very small.
C) Spectra of the core show that it contains hot gas moving at high speeds.
D) Electromagnetic radiation from the core fluctuates rapidly.
E) All of these choices are correct.

Question 40

Which of the following is not an active galaxy?

A) Seyfert galaxies
B) radio galaxies
C) QSO's
D) Attractor voids
E) None of these choices is an active galaxy.

Question 41

What theory do astronomers think explains the activity in galaxies?

A) the explosion of a supermassive star
B) a chain reaction of supernovas
C) a cosmic worm hole
D) a supermassive black hole
E) All of these choices are correct.

Question 42

How does the prevailing model for activity explain the hot ejected gas seen in active galaxies?

A) It is shot out of a black hole.
B) It is material trapped between two orbiting black holes being gravitationally scattered.
C) It is gas evaporating from an accretion disk around a massive black hole.
D) It is energy released as matter is funneled into a black hole.
E) It is a rip in space-time from which Hawking radiation is released.

Question 43

Name the three main types of active galaxies.

A) barred spiral, irregular, and Seyfert
B) Seyfert, radio, and quasar
C) spiral, elliptical, and irregular
D) old, young, and intermediate

Question 44

Where does most of the radio emission in a radio galaxy come from?

A) the center
B) the spiral arms
C) outside the galaxy in radio lobes
D) a thin shell surrounding the galaxy

Question 45

Which of the following is a property of Seyfert galaxies?

A) Their nuclei have abnormally low luminosities.
B) They contain no gas clouds.
C) The radiation from their cores fluctuates rapidly.
D) Most are elliptical galaxies.

Question 46

Why do we think that quasars are extremely distant?

A) Their light varies rapidly.
B) Their spectra show immense redshifts.
C) They are very bright.
D) They are very faint.

Question 47

Why do we think that active galaxies have small core regions?

A) We can measure their size on the sky, which means they are small and near.
B) They emit radio waves that larger objects cannot do.
C) Their light varies rapidly, implying small radius.
D) They are very far away, and thus are younger and less expanded.

Question 48

A spiral galaxy has a small bright central region and its spectrum shows that it contains hot, rapidly moving gas. It is most likely a _________ galaxy.

A) barred spiral
B) Seyfert
C) radio
D) BL Lac
E) quasar

Question 49

What do most astronomers now think explains why active galaxies are so energetic?

A) an immense black hole
B) intense magnetic fields
C) a supernova explosion
D) None of these choices is correct.

Question 50

A supercluster is a ___________.

A) group of globular star clusters
B) group of open star clusters
C) cluster of several dozen galaxy clusters
D) All of these choices are correct.

Question 51

The Local Group is______________________.

A) the name of the spiral arm of our Galaxy in which the Sun is located
B) the group of planets around the Sun
C) a star cluster to which the Sun belongs
D) a cluster of galaxies in which the Milky Way is located

Question 52

Voids are

A) spaces between stars.
B) spaces between galaxies within a cluster.
C) huge regions of space with few or no galaxies.
D) regions in the centers of galaxies containing many black holes.

Question 53

Our Milky Way is part of _________ which has about ____ member galaxies.

A) the coma cluster; 500
B) the Pleiades; 3
C) the local group; 30
D) the beehive association; 100

Question 54

What is a void?

A) a region in the universe where there are almost no galaxies
B) a part of the sky where no galaxies are visible to us because of obscuring dust in the milky way
C) a part of the sky that astronomers cannot observe due to bright emission from interstellar dust
D) another name for a dark nebula

Question 55

A region in the Universe where there are almost no galaxies is called a ____.

A) void
B) dark nebula
C) zone of avoidance
D) supermassive black hole

Question 56

The Local Group

A) contains about 30 member galaxies.
B) has the Milky Way as its center.
C) is the globular cluster to which the Milky Way belongs.
D) is a supercluster.
E) None of these choices is correct.

Question 57

The Local Group

A) contains about 30 member galaxies.
B) has the Milky Way as its center.
C) is the small cluster to which the Milky Way belongs.
D) is a supercluster.
E) None of these choices is correct.

Question 58

What is the name of the galaxy cluster to which the Milky Way belongs?

A) the local group
B) M31
C) the Sagittarius cloud
D) the Scorpius group
E) the Virgo cluster

Question 59

What holds galaxy clusters together?

A) the pressure from the cosmic background radiation
B) the cosmological constant force
C) gravity
D) the strong force
E) the electromagnetic force

Question 60

What is the "rotation curve" of a galaxy?

A) It is a graph of the orbital velocities at various distances from the center of the galaxy.
B) It is a graph of the speed at the center of the galaxy.
C) It is the recession speed of galaxies at various distances from the Milky Way.
D) It is the speed of the globular clusters in a galaxy.

Question 61

What is one piece of evidence for dark matter?

A) the presence of neutrinos
B) the fact that the rotation curves of most galaxies become flat at large distances from the center
C) the existence of many planetary systems
D) the existence of many dark cool dust clouds that do not emit radiation

Question 62

In attempting to find the missing matter that seems to be required to explain observed properties of galaxies and clusters, astronomers have been able to rule out which populations?

A) black holes
B) hot and cold gas
C) weakly interacting massive particles
D) dead white dwarfs

Question 63

Which of the following provides evidence for the existence of dark matter?

A) The orbital speeds of stars in galaxies are higher than what can be accounted for by the detectable mass in the galaxy.
B) The orbital speeds of galaxies in clusters are higher than what can be accounted for by the detectable mass of the cluster.
C) the ability of rich galaxy clusters to prevent their hot gases from expanding
D) All of these choices are correct.

Question 64

Which of the following objects are difficult to model as existing in large enough numbers to significantly explain the effects of "dark matter"?

A) black holes
B) planetesimal-sized objects
C) cold white dwarfs
D) All of these choices are correct.

Question 65

The observation that outer parts of galaxies rotate faster than the observable mass within their orbit can pull them implies that _____________.

A) galaxies are unstable
B) all galaxies will eventually develop a bulge
C) In time, galaxies will develop spiral arms
D) the masses of galaxies are larger than their luminous mass
E) None of these choices is correct.

Question 66

In their search for dark matter, astronomers can exclude the possibility that cold gas clouds account for dark matter because cold gas clouds ______________.

A) have very low mass
B) would be detectable by radio telescopes
C) do not produce gravitational force
D) would emit visible spectral lines
E) would slow down the rotation of the galaxy

Question 67

Astronomers believe that dark matter exists because

A) they can detect it with radio telescopes.
B) the outer parts of galaxies rotate faster than expected on the basis of the material visible in them.
C) the galaxies in clusters move slower than expected on the basis of the material visible in them.
D) it is the only way to explain the black holes in active galaxies.
E) All of these choices are correct.

Question 68

Astronomers believe that dark matter exists because.

A) they can detect it with radio telescopes.
B) the outer parts of galaxies rotate faster than expected on the basis of the material visible in them.
C) the galaxies in clusters move slower than expected on the basis of the material visible in them.
D) it is the only way to explain the black holes in active galaxies.
E) All of these choices are correct.

Question 69

What is a gravitational lens?

A) a star that is eclipsed by one of its planets
B) a massive object that bends the space around it, causing light passing it to bend
C) an extremely massive refractor telescope
D) a lens that is affected by gravity

Question 70

Why is it difficult to use the method of standard candles to find the distance to galaxies?

A) It is difficult to isolate the light of a single star from the galaxy.
B) There are no known standard candles outside of our galaxy.
C) Standard candles are too bright to be used for all but the farthest galaxies.
D) All of these choices are correct.

Question 71

Why do galaxy collisions lead to star formation?

A) Stars collide with each other, explode, and their gas creates new stars.
B) Interstellar clouds are ignited by passing stars from the other galaxy.
C) Interstellar clouds collide and become highly compressed.
D) All of these choices are correct.

Question 72

The apparent shape of an elliptical galaxy is an effect of perspective.

Question 73

It is expected that only elliptical galaxies have a massive black hole at their center.

Question 74

The Hubble law does not apply for nearby galaxies.

Question 75

Irregular galaxies, although small in size, have lots of star formation taking place in them.

Question 76

When viewed through a small telescope, galaxies appear bright, with a definitive edge.

Question 77

The NGC (New General Catalog) is a compilation started by Herschel, and lists galaxies and other astronomical objects.

Question 78

Edwin Hubble was the first to classify galaxies in three main types: spirals, ellipticals and irregulars.

Question 79

Hubble's law can be applied to measure the distance of the constellation of Orion.

Question 80

The blue color seen in some galaxies is an indication that star formation is occurring in those galaxies.