26 (2)

Question 1

Elliptical galaxies consist almost entirely of …………. stars and have shapes that are ……….. or ……….. (somewhat squashed spheres) (Figure 26.7). They contain no trace of spiral arms. Their light is dominated by ………… ……….. stars

Answer 1

old

spheres / ellipsoids

older reddish

Question 2

In the larger nearby ellipticals, many ………… clusters can be identified.

Dust and emission nebulae are inconspicuous in elliptical galaxies, but many do contain a small amount of ……… …….

Answer 2

globular

interstellar matter.

Question 3

Elliptical galaxies show various degrees of flattening, ranging from systems that are approximately spherical to those that approach the flatness of spirals.

Answer 3

R 2

Question 4

The rare giant ellipticals (for example, ESO 325-G004 in Figure 26.7) reach luminosities of ………..L_Sun. The mass in a giant elliptical can be as large as ……….. M_Sun.

Answer 4

10¹¹ / 10¹³

Question 5

The diameters of these large Elliptical galaxies extend over several …………. ………….. light-years and are considerably larger than the largest spirals.

Answer 5

hundred thousand

Question 6

Although individual stars orbit the center of an elliptical galaxy, the orbits are not all in the ……….. ……….., as occurs in spirals. Therefore, ellipticals don’t appear to rotate in a systematic way, making it difficult to estimate how much ………. …….. they contain.

Answer 6

same direction

dark matter

Question 7

We find that elliptical galaxies range all the way from the giants, to ……………., which may be the most common kind of galaxy.

Answer 7

dwarfs

Question 8

1. Typically, irregular galaxies have …………. masses and luminosities than spiral galaxies.
2. Irregular galaxies often appear disorganized, and many are undergoing relatively intense ……… ……… activity.
3. They contain both young ………….. …… stars and old …………. ……. stars.

Answer 8

1. lower
2. star formation
3. population I / population II

Question 9

The two best-known irregular galaxies are the Large ………… ……… and Small ……….. ……….

Answer 9

Magellanic Cloud / Magellanic Cloud

Question 10

Although not visible from the United States and Europe, Large Magellanic Cloud and Small Magellanic Cloud are prominent from the …………… Hemisphere, where they look like wispy clouds in the night sky. Since they are only about one-tenth as distant as the Andromeda galaxy,

Answer 10

Southern

Question 11

Large Magellanic Cloud and Small Magellanic Cloud present an excellent opportunity for astronomers to study nebulae, star clusters, variable stars, and other key objects in the setting of another galaxy. For example, the Large Magellanic Cloud contains the 30 ………… ……….. (also known as the ……….. ………), one of the largest and most luminous groups of supergiant stars known in any galaxy.

Answer 11

Doradus complex / Tarantula Nebula

Question 12

A large trail of debris from this interaction between the Milky Way and the Small Magellanic Cloud has been strewn across the sky and is seen as a series of gas clouds moving at abnormally high velocity, known as the ………… …………

Answer 12

Magellanic Stream

Question 13

Wouldn’t it be nice if every elliptical galaxy evolved into a spiral, for example, just as every main-sequence star evolves into a red giant? Several simple ideas of this kind were tried, some by Hubble himself, but none stood the test of time (and observation).

Answer 13

R 2

Question 14

The technique for deriving the masses of galaxies is basically the same as that used to estimate the mass of the Sun, the stars, and our own Galaxy. We measure how ………. objects in the outer regions of the galaxy are orbiting the center, and then we use this information along with ………. ……… …….. to calculate how much mass is inside that orbit.

Answer 14

fast / Kepler’s third law