CP 20 Galaxies and the Foundation of Modern Cosmology Flashcards
Which of the following is not one of the three major categories of galaxies?
globular galaxies
spiral galaxies
elliptical galaxies
irregular galaxies
globular
Which of the following best describes the status of the Milky Way in our Local Group of galaxies?
It is quite average among the galaxies in the group.
It is one of the two largest galaxies in the group.
It is one of about a dozen large spiral galaxies in the group.
It is by far the largest galaxy in the group.
It is one of the two largest galaxies in the group.
Galaxies with disks but no evident spiral arms are called __________.
lenticular galaxies
Which of these galaxies would you most likely find at the center of a large cluster of galaxies?
a large spiral galaxy
a large elliptical galaxy
a small irregular galaxy
a large elliptical galaxy
Does Hubble’s law work well for galaxies within the Local Group? Why or why not?
No, because galaxies in the Local Group are gravitationally bound together.
Overall, what is our most accurate technique for measuring the distance to a nearby star?
stellar parallax
Suppose an elliptical galaxy is so far away that we cannot see even its brightest stars individually. Which of the following techniques might allow us to measure its distance?
radar ranging
using a white dwarf supernova as a standard candle
parallax
using Cepheid variables as standard candles
using a white dwarf supernova as a standard candle
A standard candle is __________.
a light source of known luminosity
Which kind of object is the best standard candle for measuring distances to extremely distant galaxies?
a white dwarf supernova
What two observable properties of a Cepheid variable are directly related to one another?
the period between its peaks of brightness and its luminosity
What does Hubble’s law tell us?
The more distant a galaxy, the faster it is moving away from us.
Cosmological redshift is the result of __________.
the expansion of the universe
Although the entire universe may be much larger than our observable universe, we can see only within our observable universe. The “boundary” of our observable universe is called __________.
the cosmological horizon
Which of these galaxies is most likely to be oldest?
- a galaxy in the Local Group
- a galaxy observed at a distance of 5 billion light-years
- a galaxy observed at a distance of 10 billion light-years
a galaxy in the Local Group
If we say that a galaxy has a lookback time of 1 billion years, we mean that __________.
its light traveled through space for 1 billion years to reach us
