CH26
Which of the following statements about the different types (shapes) of galaxies is correct?
collisions and mergers between galaxies can sometimes change a galaxy's type (shape)
Which of the following was not done by Edwin Hubble?
discovering the relationship between period and luminosity of a cepheid variable
Which type of galaxy is very difficult to see, but (astronomers recently realized) may be very common?
dwarf elliptical
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:
elliptical
Which type of galaxy is observed to contain mostly older stars?
elliptical
The Tully-Fisher method for measuring the distance to galaxies relies on the observed relationship between the luminosity of a spiral galaxy and
its rotational velocity (as determined from the width of the 21-cm line)
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
more
Compared to the mass of our own Milky Way Galaxy, the total mass we estimate for the Andromeda Galaxy is
somewhat bigger
Our Milky Way Galaxy is what type of galaxy?
spiral
The type of galaxy that sometimes has a distinct bar of stars running across the central region is
spiral
The Tully-Fisher relation (looking at rotation speeds) only works for:
spiral galaxies
The new instrument that made it possible for Edwin Hubble to demonstrate the existence of other galaxies in the early 1920's was:
the 100-inch reflector on Mount Wilson
Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther a galaxy is from us, the
the faster it is moving away from us
Edwin Hubble developed a classification scheme for galaxies. By what characteristic did he classify galaxies?
their shape
Among irregular galaxies, what makes the Large and Small Magellanic Cloud especially useful for astronomers?
they are (for galaxies) very close to us, so they are easy to study
The reason type Ia supernovae are useful to astronomers for determining distances to other galaxies is that
they are very bright, and generally reach the same peak luminosity
The Andromeda Galaxy (our nearest spiral neighbor) has spectral lines that show a blue shift. From this we may conclude that:
this particular nearby galaxy is moving toward us
Which of the following objects is considered useful to astronomers as a "standard bulb" for determining distances?
type la supernovae
Which of the following is NOT a characteristic of a spiral galaxy?
when we take spectra of its stars, they have far less of the heavier elements than the Sun
Before you can use Hubble's Law to get the distance to a galaxy, what observation must you make of that galaxy?
you must take a spectrum of the galaxy and measure the red shift
The astronomer who assisted Edwin Hubble at the Mount Wilson Observatory and helped him establish the expansion of the universe was:
Milton Humason
Why is the use of Hubble's Law to measure distances to galaxies so important to astronomers?
Most galaxies are so far away, the only way to get distances to them is to use Hubble's Law
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
hydrogen
The first astronomer to show that spiral nebulae (today called spiral galaxies) have large Doppler shifts was
Vesto Slipher
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?
finding Cepheid variables and measuring their periods
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?
galaxies contain many more stars that shine much less brightly than the Sun
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?
by observing a Cepheid variable in a nearby galaxy and using it to get the distance
What method would astronomers use to find the distance to a galaxy so far away that individual stars are impossible to make out (resolve)?
finding the redshift and using Hubble's Law
Which of the following statements about the implications of Hubble's Law is FALSE?
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
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 central bulge with a bar of stars in the middle
If a galaxy contains a great deal of "dark matter," what will that do the galaxy's mass-to-light ratio?
increase it quite a bit
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
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?
obtain the speed at which stars or gas near the outer regions of the galaxy are moving around