Deck 26: Galaxies

Question 1

About two thirds of the nearby spiral galaxies (which we can study in more detail) don't have a round central bulge, but instead show

A) no central bulge at all, just a uniform galaxy
B) a central bulge with a bar of stars in the middle
C) a central bulge with a completely irregular and unsymmetric shape
D) a central bulge with 2 giant jets coming out larger than the galaxy
E) you can't fool me; all spirals have a round central bulge

Answer 1

a central bulge with a bar of stars in the middle

Question 2

Our Milky Way Galaxy is what type of galaxy?

A) spiral
B) elliptical
C) dwarf elliptical
D) irregular
E) giant elliptical

Answer 2

spiral

Question 3

The new instrument that made it possible for Edwin Hubble to demonstrate the existence of other galaxies in the early 1920's was:

A) the Hubble Space Telescope (that's why we named it after Hubble!)
B) the 300-ft radio telescope in West Virginia
C) a kind of electronic detector called a CCD
D) the 100-inch reflector on Mount Wilson
E) an infra-red telescope carried aboard one of the early airplane flights by the Wright Brothers
Section 26.2: Types of Galaxies

Answer 3

the 100-inch reflector on Mount Wilson

Question 4

If a galaxy contains a great deal of dark matter, then, compared to the mass-to-light ratio of the inner part, the mass-to-light ratio of the whole galaxy will be

A) less
B) more
C) the same
D) it depends on the type of galaxy
E) it depends on the galaxy's red-shift
Section 26.4: The Extragalactic Distance Scale

Question 5

What method would astronomers use to find the distance to a galaxy so far away that individual stars are impossible to make out (resolve)?

A) parallax
B) Cepheid variables
C) using the x-ray emission from the entire galaxy
D) finding the red?shift and using Hubble's Law
E) the turnoff point of the main sequence on an H-R diagram

Question 6

Compared to the mass of our own Milky Way Galaxy, the total mass we estimate for the Andromeda Galaxy is

A) a lot smaller
B) a little bit smaller
C) exactly the same
D) somewhat bigger
E) not something we can measure

Question 7

Which type of galaxy is very difficult to see, but (astronomers recently realized) may be very common?

A) spiral
B) elliptical
C) dwarf elliptical
D) irregular
E) none of the above

Question 8

The type of galaxy that consists almost entirely of old stars and is thus less blue (more yellow and reddish) than the other types is:

A) spiral
B) elliptical
C) irregular
D) barred spiral
E) all of the above consist almost entirely of old stars

Question 9

Which of the following objects is considered useful to astronomers as a "standard bulb" for determining distances?

A) type Ia supernovae
B) planets that resemble Earth
C) K-type stars
D) the brightness of the bulge in a galaxy's center
E) the size of the largest diameter open cluster in a galaxy

Question 10

Which of the following is NOT a characteristic of a spiral galaxy?

A) most of its material is in the shape of a flattened disk
B) it has quite a bit of gas and dust in it
C) it has young stars and bright emission nebulae
D) when we take spectra of its stars, they have far less of the heavier elements than the Sun
E) the bright stars in it can be seen organized into distinct spiral arms

Question 11

Which is one reason that the typical galaxy's mass-to-light ratio (in units of the Sun's mass over the Sun's luminosity) generally greater than 1?

A) galaxies contain mostly stars much brighter than the Sun
B) galaxies contain mostly stars much more massive than the Sun
C) galaxies contain many more stars that shine much less brightly than the Sun
D) most of the mass in a galaxy is in the form of dust
E) this is an unsolved problem in astronomy; scientists have no clue

Question 12

Which type of galaxy is observed to contain mostly older stars?

A) spiral
B) elliptical
C) dwarf elliptical
D) irregular
E) none of the above

Question 13

The type of galaxy that sometimes has a distinct bar of stars running across the central region is

A) spiral
B) elliptical
C) dwarf elliptical
D) irregular
E) all of the above can have clear, distinct central bars

Question 14

Which of the following statements about the different types (shapes) of galaxies is correct?

A) whatever type a galaxy is at its birth, that's what it will be for all time
B) all galaxies start out as ellipticals, but some later evolve to be spirals and irregulars
C) 90% of all galaxies are spirals (including our Milky Way); the other two types are very unusual
D) collisions and mergers between galaxies can sometimes change a galaxy's type (shape)
E) what type we see a galaxy to be just depends on the angle at which we happen to see it; all galaxies look roughly the same in shape
Section 26.3: Properties of Galaxies

Question 15

Among irregular galaxies, what makes the Large and Small Magellanic Cloud especially useful for astronomers?

A) they are (for galaxies) very close to us, so they are easy to study
B) they are among the biggest irregular galaxies ever found
C) they have a regular shape, but it is so complicated it was hard to figure out
D) they do not contain any young stars at all, only really old ones
E) their shape resembles a map of Bayonne, New Jersey

Question 16

If a galaxy contains a great deal of "dark matter," what will that do the galaxy's mass-to-light ratio?

A) increase it a small amount
B) decrease it a small amount
C) increase it quite a bit
D) decrease it quite a bit
E) not affect it in any way (since it's dark matter)

Question 17

Edwin Hubble developed a classification scheme for galaxies. By what characteristic did he classify galaxies?

A) their brightness
B) their overall color
C) their shape
D) their abundance of the element iron
E) their Doppler Shift

Question 18

One of the most important observations in the history of astronomy was the one by Edwin Hubble that established that there are other galaxies, quite removed from the Milky Way. How did Hubble show this?

A) by debating with Harlow Shapley and being more eloquent
B) by observing a supernova explosion in a nearby galaxy, using it as a "standard bulb"
C) by observing a Cepheid variable in a nearby galaxy and using it to get the distance
D) by measuring the distances to many globular clusters using parallax
E) by going to see Einstein, who knew the answers to these kinds of questions

Question 19

One of the main projects being carried out by the Hubble Space Telescope is to measure the distances of galaxies located in groups dozens of millions of lightyears away. What method do astronomers use with the Hubble to find such distances?

A) constructing H-R diagrams
B) measuring the parallax over a period of a decade or so
C) finding Cepheid variables and measuring their periods
D) measuring the x-rays given off by the accretion disks around massive black holes
E) measuring the amount of dust in the disk of the galaxy

Question 20

A graduate student in astronomy needs to measure the mass of a spiral galaxy she is studying for her PhD thesis. Which of the following observations would be important for her to make?

A) determine whether or not there is evidence for a massive black hole at the galaxy's center
B) construct an H-R diagram for a prominent open cluster in the galaxy's disk
C) measure the gamma-ray emission from the galaxy
D) compare the overall color of the galaxy to other galaxies of the same type
E) obtain the speed at which stars or gas near the outer regions of the galaxy are moving around

Question 21

Why is the use of Hubble's Law to measure distances to galaxies so important to astronomers?

A) They have NO other way of measuring distances to galaxies - absolutely none
B) Many galaxies don't move away from us, so when we find one that does, it's really a big deal
C) Most galaxies are so far away, the only way to get distances to them is to use Hubble's Law
D) The other ways of getting distances only work for really far away galaxies; so the Hubble Law is the only way to measure distances to nearby galaxies
E) It's stretching the truth to say that Hubble's Law is a really important way to get distances to galaxies; really, it's no more important than any other method

Question 22

The reason type Ia supernovae are useful to astronomers for determining distances to other galaxies is that

A) they only occur in spiral galaxies, for which no other way of getting distances is available
B) it is easy to measure the blueshift produced by such explosions
C) they are much larger than many other objects that can be seen in galaxies
D) they are very bright, and generally reach the same peak luminosity
E) they produce very energetic pulsars whose radio radiation can be detected across vast distances

Question 23

The Tully-Fisher relation (looking at rotation speeds) only works for:

A) elliptical galaxies
B) the very closest galaxies, within a few dozen million light-years
C) galaxies that have a Type Ia supernova explosion in them
D) spiral galaxies
E) galaxies that we are observing from right around the time of the big bang

Question 24

The Andromeda Galaxy (our nearest spiral neighbor) has spect?ral lines that show a blue shift. From this we may conclude that:

A) the universe is no longer expanding
B) this particular nearby galaxy is moving toward us
C) this galaxy has merged with the Milky Way and is now part of it
D) this particular nearby galaxy is moving away from us
E) this galaxy has an unusual number of very bright and hot O-type stars in it

Question 25

The astronomer who assisted Edwin Hubble at the Mount Wilson Observatory and helped him establish the expansion of the universe was:

A) Vesto Slipher
B) Harlow Shapley
C) Milton Humason
D) Immanuel Kant
E) James Kirk

Question 26

Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther a galaxy is from us, the

A) brighter it looks
B) bluer its color
C) the later in its life we are seeing it
D) the larger its halo is
E) the faster it is moving away from us

Question 27

In a distant galaxy, whose light is just arriving from 10 billion light years away, our spectroscope should reveal that the most common element is

A) helium
B) carbon
C) hydrogen
D) iron
E) Einsteinium

Question 28

Before you can use Hubble's Law to get the distance to a galaxy, what observation must you make of that galaxy?

A) you must find a Cepheid variable star in the galaxy
B) you must take a spectrum of the galaxy and measure the red shift
C) you must measure how strongly the galaxy emits radio waves at a wavelength of 21 centimeters
D) you must find a Type Ia supernova that is exploding in that galaxy
E) all you need to do is look at the galaxy through any telescope

Question 29

According to Hubble's Law, if two galaxies are not part of our Local Group, and galaxy B is three times farther away from us as Galaxy A, then Galaxy B will

A) move toward us three times faster than A
B) move away from us nine times faster than A
C) move away from us three times faster than A
D) move toward us nine times faster than A
E) move away from us at about the same speed as A

Question 30

Which of the following was not done by Edwin Hubble?

A) measuring the distance to the Andromeda "nebula"
B) classifying the galaxies by their shapes
C) establishing the expansion of the universe
D) discovering the law that the motion of the galaxies away from us follows
E) discovering the relationship between period and luminosity of a cepheid variable

Question 31

The first astronomer to show that spiral nebulae (today called spiral galaxies) have large Doppler shifts was

A) Edwin Hubble
B) Vesto Slipher
C) Percival Lowell
D) Christian Doppler
E) Harlow Shapley

Question 32

The Tully-Fisher method for measuring the distance to galaxies relies on the observed relationship between the luminosity of a spiral galaxy and

A) its rotational velocity (as determined from the width of the 21-cm line)
B) its number of high-energy sources (as determined from the total gamma-ray emission)
C) the size of its supernova remnants (as determined from radio maps)
D) the number of globular clusters (as determined from high-resolution images)
E) the number of companion galaxies found directly around it
Section 26.5: The Expanding Universe

Question 33

Which of the following statements about the implications of Hubble's Law is FALSE?

A) the law implies that the whole universe must be expanding
B) the law can be used to measure distances to remote galaxies for which we can measure a Doppler shift
C) the law does NOT require us to be at the center of the expanding universe
D) if you were observing the universe from a distant galaxy, you would NOT see all the galaxies (except those in your own group) moving away from YOU
E) although galaxies move away from each other, they themselves are not expanding in size