WQ #26

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

a. its rotational velocity (as determined from the width of the 21-cm line)

Our Milky Way Galaxy is what type of galaxy? a. spiral b. elliptical c. dwarf elliptical d. irregular e. giant elliptical

a. spiral

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

b. a central bulge with a bar of stars in the middle

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

b. you must take a spectrum of the galaxy and measure the red shift

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

c. their shape

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 redshift and using Hubble's Law e. the turnoff point of the main sequence on an H-R diagram

d. finding the redshift and using Hubble's Law

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

d. somewhat bigger

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

a. spiral

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

a. they are (for galaxies) very close to us, so they are easy to study

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

a. type Ia supernovae

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

b. elliptical

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

b. more

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

c. Most galaxies are so far away, the only way to get distances to them is to use Hubble's Law

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

e. the faster it is moving away from us

The Andromeda Galaxy (our nearest spiral neighbor) has spectral 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

b. this particular nearby galaxy is moving toward us

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

c. dwarf elliptical

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

c. finding Cepheid variables and measuring their periods

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

c. hydrogen

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

c. move away from us three times faster than A

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

e. obtain the speed at which stars or gas near the outer regions of the galaxy are moving around