Chapter 15 Flashcards
We can in principle measure the expansion rate by studying galaxies in many different directions in space and at different times of year. If we compare such observations, we would find that the expansion rate is __________.
the same no matter when or in which direction we measure it
Suppose a collision strips gas out of a spiral galaxy. Why would this tend to change the spiral galaxy into an elliptical galaxy?
a galaxy cannot have a disk if it doesn’t have gas
High density tends to lead to more rapid star formation in a protogalactic cloud. Why does this rapid star formation tend to lead to an elliptical galaxy, rather than a spiral galaxy?
Rapid star formation means that there may not be enough gas left to make a disk.
High angular momentum leads to faster rotation. Why does faster rotation tend to lead to a spiral galaxy, rather than an elliptical galaxy?
Faster rotation leads to collisions among gas particles that cause the gas to settle into a spinning disk, rather than a more spread out cloud.
Which of these galaxies would you most likely find at the center of a large cluster of galaxies?
a large elliptical galaxy
If all the stars on the main sequence of a star cluster are typically only one-hundredth as bright as their main-sequence counterparts in the Hyades Cluster, then that cluster’s distance is
10 times as far as the Hyades’s distance.
Which kind of object is the best standard candle for measuring distances to extremely distant galaxies?
a white dwarf supernova
