astro chp 15

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

Elliptical

As we progress in the Hubble classification sequence of spiral galaxies from type Sa to Sb to Sc, how do the physical characteristics change

The central bulges become smaller, while the spiral arms become less tightly wound

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

They have random orbits in three dimensions

Which type of galaxy exhibits the largest range of sizes and masses

elliptical

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

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

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

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

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

Type I supernovae

What is the criterion for a group of galaxies to be considered a cluster

Galaxies in a cluster are bound together by their mutual gravitational pull

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

increases; apparent recessional velocity

Which of the following is NOT an implication of Hubble’s law

The Milky Way Galaxy is at the center of the Universe

Active galaxies give off more energy than "normal" galaxies in what part of the electromagnetic spectrum

All of the above

What characteristic of some radio lobe galaxies suggests that their energy emission changes over time

They display "blobs" of material along their lengths that indicate this material was ejected in bursts

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

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

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

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

What is the best explanation of the differences between a lobe radio galaxy and a core-dominated radio galaxy

There is no real difference. When we look at core-dominated radio galaxies, we are looking at the galaxy through one of its lobes and along one of the jets

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

a spiral galaxy

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

redshifted by a larger amount than expected

The fact that the energy output of active galactic nuclei can vary significantly over a short time indicates that the central object emitting the energy is which of the following

much less than a parsec across

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

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

The large amount of synchrotron radiation coming from an active galaxy indicates the presence of what in the active galaxy

A powerful magnetic field

Using the method of standard candles, we can, in principle, find the distance to a campfire if we know

the number of logs used

If the light from a galaxy fluctuates in brightness very rapidly, the region producing the radiation must be

very small

Active galaxies are very luminous because they

contain black holes in their cores

Quasar spectra

are strongly redshifted

According to Figure 15.18 (Galaxy Energy Spectra) in the textbook, active galaxies

emit large amounts of energy at all wavelengths

Most galaxies are spirals like the Milky Way

F

Most elliptical galaxies contain only young stars

F

Type I supernovae can be used to determine distances to galaxies

T

Most galaxies are receding from the Milky Way Galaxy

T

Within 30 Mpc of the Sun, there are about

few thousand galaxies

Hubble’s law states that

the greater the distance to a galaxy, the greater is the galaxy’s redshift

Irregular galaxies, although small, have lots of star formation taking place in them

T

Hubble’s law can be used to determine distances to the farthest objects in the universe

T

Active galaxies can emit thousands of times more energy than our own Galaxy

T

If the galaxy in Figure 15.10 (Galaxy Rotation) in the textbook were smaller and spinning more slowly, then the igure should be redrawn to show

a narrower combined line

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