Phys 1403 - Final

Front 1

The third image in the interactive photo (with the most detailed view of the galactic center) is labeled "gas disk." Which of the following best describes what we are seeing in this photo?

Back 1

The black hole is located deep within the bright central region, and around this region we see gas that is orbiting the central black hole.

Front 2

Why do astronomers hypothesize that a massive black hole lies at the center of M 87?

Back 2

A very small region at the center of M 87 releases an enormous amount of energy.

Front 3

Assuming that the bright core of M 87 is powered by a supermassive black hole, which of the following best describes the source of energy that makes the core appear so bright?

Back 3

Gravitational potential energy is converted to thermal energy as matter from the surrounding gas disk spirals into the central black hole.

Front 4

The graph shows that galaxies with high speeds as measured from Earth are __________.

Back 4

Moving away from Earth and are farther from Earth than galaxies with lower speeds

Front 5

By looking at the graph, what can we say about the galaxies that have the lowest speeds?

Back 5

They are moving away from Earth and are closer to Earth than galaxies with high speeds

Front 6

Suppose that galaxy B is twice as far from Earth as galaxy A. Hubble’s law predicts that galaxy B will be moving away from Earth with approximately _____.

Back 6

Twice the velocity of galaxy A

Front 7

Imagine that when we looked out into the universe we found that the light from all galaxies was blueshifted (rather than redshifted) and that the light from the most distant galaxies was blueshifted by the greatest amount. Which statement best describes what we would conclude about the motions of galaxies in this case?

Back 7

All are moving toward Earth, with distant galaxies moving faster than nearby galaxies.

Front 8

The age of the universe is related to the slope of the graph of Hubble’s law, and current data put the age of the universe at about 14 billion years. Suppose that future observations showed that the slope of Hubble’s law on the graph is actually steeper than that shown. In that case, the age of the universe would be _________ than 14 billion years because the universe is expanding ______ than current data suggest. (Each choice gives words to fill in the two blanks, separated by a slash.)

Back 8

Younger / more rapidly

Front 9

The fact that the energy output of active galactic nuclei can be highly variable indicates that the central object emitting the energy is which of the following?

Back 9

Much less than a parsec across

Front 10

Except for the nucleus, what does a Seyfert galaxy look like?

Back 10

A spiral galaxy

Front 11

The Tully-Fisher relation uses the close correlation between the rotational speed of a spiral galaxy and its luminosity as a distance indicator. Why does this correlation exist?

Back 11

The greater the mass of a galaxy, the faster it spins, and the more mass there is to give off light.

Front 12

Which of the following types of galaxies has experienced no significant star formation during the last 10 billion years?

Back 12

Elliptical

Front 13

Which of the following statements describes the orbits of stars within most elliptical galaxies?

Back 13

They move in random directions with respect to the galaxy itself.

Front 14

Why do errors and uncertainties in distance measurements get bigger the farther out we measure?

Back 14

The techniques used to measure far distances are calibrated by using more local measurements; therefore, any errors accumulate.

Front 15

What is the Tully-Fisher relation?

Back 15

It relates rotational speeds of galaxies as measured by the broadness of their emission lines to their luminosities.

Front 16

Which of these standard candles has/have been used to determine distances to the most distant galaxies?

Back 16

Type I supernovae

Front 17

The Virgo Cluster is about three times the diameter of the Local Group; instead of nearly 50 galaxies, how many does it contain?

Back 17

2500

Front 18

According to Hubble's law, as the distance to galaxies ________, the ________ increases.

Back 18

Increases; apparent recessional velocity

Front 19

From Hubble's law, what single observation of a galaxy is needed to determine its distance from us?

Back 19

Recessional velocity

Front 20

What is observed that connects radio emissions in the galactic nucleus with the emissions in the halo or radio lobes?

Back 20

There is a jet of matter coming out of the nucleus, which often points toward the lobes.

Front 21

How does the energy output from active galactic nuclei differ from the energy output from normal galaxies?

Back 21

The emission of active galactic nuclei is nonstellar, whereas the emission of a normal galaxy is stellar.

Front 22

Early attempts to explain the spectra of quasars were unsuccessful because the spectra were which of the following?

Back 22

Redshifted by a larger amount than expected

Front 23

Which of the following is NOT a characteristic of an active galaxy?

Back 23

A regular, rapid pattern of radio frequency and optical emission peaks ranging from milliseconds to seconds in repetition rate

Front 24

What effect is thought to be due to the presence of dark matter around spiral galaxies?

Back 24

The rotation rates of spiral galaxies and orbital interactions among galaxies within clusters suggest the presence of extra mass around them.

Front 25

What ingredients are needed to make a quasar?

Back 25

A black hole and enough fuel to power it

Front 26

How did large galaxies form?

Back 26

From the collisions and mergers of smaller galaxies

Front 27

The term starburst refers to which of the following astrophysical phenomena discussed in this chapter?

Back 27

Concentrated, intense star formation activity that occurs within galaxies as a result of gravitational interactions with other galaxies or other internal instability

Front 28

What is the defining characteristic of starburst galaxies?

Back 28

They have a large number of young stars.

Front 29

What is unusual about the results of mass determinations of clusters of galaxies?

Back 29

There is much more mass than can be accounted for by the visible galaxies.

Front 30

What is the estimated percentage of dark matter in the universe?

Back 30

90 percent

Front 31

What do astronomers believe is the result of a merger between two spiral galaxies?

Back 31

An elliptical galaxy

Front 32

Which galaxies are relatively rare in regions of high galaxy density?

Back 32

Spiral

Front 33

When galaxies collide, what happens in general to the stars contained within them?

Back 33

They mostly pass by the stars in the other galaxy without colliding.

Front 34

Does every bright galaxy have a central supermassive black hole?

Back 34

Yes. Essentially every bright galaxy has a central supermassive black hole.

Front 35

Does the mass of a supermassive black hole correlate with any other part of a galaxy?

Back 35

Yes. It correlates well with the mass of the galactic bulge.

Front 36

If quasars are among the most distant objects in the universe, then they must also be which of the following?

Back 36

Most luminous

Front 37

Which of the following does NOT describe galaxies at very large redshifts?

Back 37

They appear redder than nearby galaxies.

Front 38

What do astronomers learn from a redshift survey?

Back 38

The redshift gives us the distance to galaxies.