17-2 Types of Galaxies

What is the main purpose of classifying spiral galaxies into different types?

• To help visualize what they look like

• To determine their age

• To measure their distance from Earth

• To calculate their mass

What characteristic is prominent in Sa galaxies?

• A big central bulge and smooth, broad spiral arms

• A small central bulge and narrow arms

• A moderately-sized central bulge

• No central bulge

What is a characteristic of Spiral type C (Sc) galaxies?

• Very small central bulge and narrow, well-defined arms

• Large central bulge and tightly wound arms

• Moderately-sized central bulge

• No spiral arms

What analogy is used to explain the classification of spiral galaxies?

• Cars like Porsche and Hummer

• Birds like eagles and sparrows

• Trees like oak and pine

• Rivers like Nile and Amazon

What is the characteristic of the arms in Spiral type A (Sa) galaxies?

• Very tightly wound

• Very loosely wound

• Moderately well-defined

• Not present

What percentage of the mass of a Sc galaxy is made up of interstellar dust and gas?

• 10%

• 25%

• 50%

• 75%

What is the main ingredient for star formation in galaxies?

• Dark matter

• Interstellar dust and gas

• Cosmic rays

• Black holes

What is the main difference between barred spiral galaxies and normal spiral galaxies?

• The size of the central bulge

• The presence of a bar-shaped region

• The number of spiral arms

• The color of the stars

What is the relationship between interstellar dust and star formation?

• More dust means less star formation

• More dust means more star formation

• Dust has no effect on star formation

• Dust prevents star formation

What is a key feature of Sc galaxies?

• They have a large central bulge.

• They have no spiral arms.

• They have a very small central bulge and narrow, well-defined arms.

• They have a bar-shaped region.