CP 21 Galaxy Evolution

Question 1

Collisions between galaxies typically unfold over a period of __________.

Answer 1

hundreds of millions of years

Question 2

Telescopes designed to study the earliest stages in galactic lives should be optimized for observations in __________.

Answer 2

infrared light

Question 3

According to observations, which type of galaxy was much more common when the universe was 2 billion years old than it is today?

Answer 3

irregular galaxies

Question 4

We can study how galaxies evolve because ______.

Answer 4

the farther away we look, the further back in time we see

Question 5

A collision between two large spiral galaxies is likely to produce

Answer 5

a large elliptical galaxy.

Question 6

What was a key assumption in our most successful models for galaxy formation?

Answer 6

Some regions of the universe were slightly denser than others.

Question 7

The distinguishing feature of a starburst galaxy is __________.

Answer 7

a rate of star formation that may be 100 or more times greater than that in the Milky Way

Question 8

why galaxy collisions should have been more common in the past than they are today

Answer 8

Galaxies were closer together in the past, because the universe was smaller.

Question 9

Which is not a general characteristic of starburst galaxies?

The observed features that cause us to classify a galaxy as a “starburst” galaxy must be only temporary phenomena in the galaxy’s history.

Supernovae occur so frequently that their effects combine to drive a galactic wind that blows material into intergalactic space.

The galaxy’s rate of star formation is many times higher than the rate of star formation in the Milky Way.

The “starburst” is thought to be caused by the presence of a supermassive black hole in the galaxy’s center.

Answer 9

The “starburst” is thought to be caused by the presence of a supermassive black hole in the galaxy’s center.

Question 10

The primary source of a quasar’s energy is

Answer 10

gravitational potential energy.

Question 11

The unusually bright centers found in some galaxies are called __________.

Answer 11

active galactic nuclei

Question 12

According to current understanding, what is a quasar?

Answer 12

an active galactic nucleus that is particularly luminous

Question 13

The luminosity of a quasar is generated in a region the size of

Answer 13

the solar system.

Question 14

TF galaxy formation and supermassive black hole formation must be related

Answer 14

T

Question 15

A quasar’s spectrum is hugely redshifted. What does this large redshift tells us about the quasar?

Answer 15

the distance to the quasar

Question 16

TF Active galactic nuclei exist tend to become less active as they age.

Answer 16

T

Question 17

Roughly what percentage of the mass-energy of in-falling matter can be converted to other forms of energy as the matter falls into a black hole?

Answer 17

10-40%

Question 18

Which of the following quasars would you expect to have the largest number of hydrogen absorption lines in its spectrum?

a quasar with a lookback time of 7 billion years

a quasar with a lookback time of 3 billion years

a quasar with a lookback time of 13 billion years

Answer 18

a quasar with a lookback time of 13 billion years

Question 19

Intergalactic hydrogen clouds are easiest to study by looking at __________.

Answer 19

absorption lines in quasar spectra