astro ch 26
The astronomer who assisted Edwin Hubble at the Mount Wilson Observatory and helped him establish the expansion of the universe was:
Milton Humason
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
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
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
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 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
Which of the following statements about the implications of Hubble's Law is FALSE? although galaxies move away from each other, they themselves are not expanding in size 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 the law implies that the whole universe must be expanding the law can be used to measure distances to remote galaxies for which we can measure a Doppler shift the law does NOT require us to be at the center of the expanding universe
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
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
Compared to the mass of our own Milky Way Galaxy, the total mass we estimate for the Andromeda Galaxy is
somewhat bigger
The type of galaxy that sometimes has a distinct bar of stars running across the central region is
spiral
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
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
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
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
