Chapter 34, Problem 2TC

Rank the following galaxy types in order of increasing transparency: elliptical, spiral, irregular.

To determine

The rank in increasing transparency of the galaxy types: elliptical, spiral, irregular.

Answer to Problem 2TC

The rank in order of increasing transparency of the galaxy type is irregular, spiral, elliptical.

Explanation of Solution

The galaxies that can be visible to humans through the telescope are classified into three main classes: elliptical, spiral, and irregular. Elliptical galaxies are the most common galaxies in the universe. The shape of these types of the galaxy is some-what spherical, with stars being more crowded towards the center. Elliptical galaxies have little gas and dust, which makes them easy to see through. The color of these galaxies decides their age as the yellow color represents the old stars and the blue color represents the hot young stars.

The second one is a spiral galaxy. The stars and the gas clouds concentrate in the spiral form in spiral galaxies, which makes it clear to see through it. Most spiral galaxies have more than two arms. Some astronomers report that spiral galaxies have spiral arms because they rotate or spin around a central axis. The Milky Way Galaxy is thought to look much like the NGC 6744 spiral galaxy.

Irregular galaxies are normally small and faint to see and are difficult to detect as compared to the other types. They tend to be full of clouds of gas and dust mixed with young and old stars.

In order to increase the transparency of different types of galaxies, the irregular galaxies are small, faint, and have the least transparency among three. The spiral galaxy ranks two in the order, which is more transparent than irregular galaxy but less transparent than elliptical galaxies. The elliptical galaxies are the most transparent as compare to others and ranks at last in the order.

Conclusion:

Therefore, the rank in order of increasing transparency of the galaxy type is: irregular, spiral, elliptical.