Cosmic Perspective Chapter 21 – Multiple Choice Set I – Flashcards
Unlock all answers in this set
Unlock answersquestion
Observations at different distances show galaxies of different ages and therefore different stages of evolution.
answer
How do observations of distant galaxies help us learn about galaxy evolution?
question
Because observations of distant objects reveal them as they were in the past.
answer
Why are telescopes sometimes called "time machines"?
question
The light from the galaxy as it was 100 million years ago and it is redshifted.
answer
I observe a galaxy that is 100 million light-years away: what do I see?
question
Hydrogen and helium filled all of space, and certain regions of the universe were slightly denser than others.
answer
Which of the following gives the 2 main assumptions of theoretical models of galaxy evolution?
question
The shock waves from the exploding supernovae of the earliest stars.
answer
Which of the following processes slowed the collapse of protogalactic clouds?
question
A dense cloud with very little angular momentum.
answer
Which of the following types of protogalactic clouds is most likely to form an elliptical galaxy?
question
The higher gas density forms stars more efficiently, so all the gas is converted into stars before a disk can form.
answer
Why is a dense cloud more likely to produce an elliptical galaxy than a spiral galaxy?
question
Elliptical galaxies at high redshifts lack young, blue stars.
answer
What evidence supports the theory that elliptical galaxies come from denser clouds?
question
3 m.
answer
If we represent the Milky Way Galaxy as the size of a grapefruit, the distance to the Andromeda Galaxy would be about
question
Galaxies were closer together in the past because the universe was smaller.
answer
Why should galaxy collisions have been more common in the past than they are today?
question
All of the above.
answer
What evidence supports the idea that a collision between two spiral galaxies might lead to the creation of a single elliptical galaxy?
question
Galaxy collisions are common and most galaxies in the universe are elliptical.
answer
Which of the following is not a strong argument for the theory that some large elliptical galaxies formed as the result of galaxy collisions?
question
A giant elliptical galaxy at the center of a dense cluster.
answer
What is a central dominant galaxy?
question
About a hundred.
answer
How many more stars does a starburst galaxy form in one year than the Milky Way?
question
Such galaxies produce so much light that they would have consumed all their gas long ago if they had always been forming stars at this high rate.
answer
Why do we believe that starburst galaxies represent a temporary stage in galaxy evolution?
question
The infrared.
answer
Starburst galaxies produce most of their light in the wavelength range of:
question
We see small galaxies in which many stars have one age and many others have another age that is billions of years older.
answer
What evidence suggests that small galaxies in our Local Group have undergone two or more starbursts in the past?
question
determining their redshifts.
answer
In the 1960s, Maarten Schmidt determined that quasars were very distant objects by:
question
The extremely bright center of a distant galaxy, thought to be powered by a massive black hole.
answer
What is a quasar?
question
Quasars are powered by the intense production of large numbers of stars that can only be sustained for a relatively short time.
answer
Which of the following is NOT true of quasars?
question
All of the above.
answer
Which of the following is evidence for supermassive black holes in active galaxies?
question
Active galactic nuclei tend to become less active as they age.
answer
The most active galactic nuclei are usually found at large distances fro us; relatively few nearby galaxies have active nuclei. What does this imply?
question
Hot gas erupting into intergalactic space from a large superbubble.
answer
What is a galactic wind?
question
About 10 light-hours across.
answer
If an object doubles its luminosity in 10 hours, how large can the emitting source of light be?
question
The X-ray source is no more than a few light-days in diameter.
answer
Suppose we observe a source of X rays that varies substantially in brightness over a period of a few days. What can we conclude?
question
Infrared observations show that many stars are forming near the centers of active galaxies.
answer
Which of the following is NOT a piece of evidence supporting the conclusion that active galactic nuclei are powered by accretion disks around massive black holes?
question
By gravity, which converts potential energy of matter falling toward a central black hole into kinetic energy, which is then converted to thermal energy by collisions among the particles of matter.
answer
How is the energy that powers radio galaxies, quasars, and other active galactic nuclei produced?
question
In hot gas in an accretion disk around a central black hole.
answer
Where are the X rays produced that are emitted by quasars and other active galactic nuclei?
question
We see hydrogen absorption lines at redshifts smaller than that of the quasar.
answer
How do we know that there are intergalactic clouds between a distant quasar and us?
question
The hydrogen line is wider and lines from heavy elements are weaker at higher redshifts.
answer
What are the typical features seen in quasar absorption lines of intergalactic clouds?
question
They may have had rocky planets around them.
answer
Which of the following cannot be true of the very first stars formed in the Universe?
question
They are more common at very great distances.
answer
All of the following are true. Which of these gives evidence that quasars were more common in the early stages of the universe?
