Elliptical Galaxies

Elliptical galaxies are one of the three main classes of galaxies, along with spiral and irregular galaxies. They are characterized by their smooth, featureless appearance and lack of distinct spiral arms. Elliptical galaxies are among the most massive galaxies in the universe and are thought to be composed mostly of older stars, with little ongoing star formation.

Characteristics of Elliptical Galaxies

• Shape: Elliptical galaxies are named for their ellipsoidal shape, which ranges from nearly spherical (E0) to highly elongated (E7).
• Stars: They are composed predominantly of old stars, with little interstellar gas and dust, which results in little ongoing star formation.
• Color: Elliptical galaxies appear reddish in color, indicating the presence of older, cooler stars.
• Size: They can vary in size, from dwarf ellipticals to supergiant ellipticals, which can be among the largest galaxies in the universe.
• Formation: It is believed that many elliptical galaxies formed through mergers of smaller galaxies, resulting in a more random distribution of stellar orbits compared to the organized spiral structure of spiral galaxies.

Study Guide

Formation and Evolution

1. What is the predominant age of stars in elliptical galaxies?

Answer: The predominant age of stars in elliptical galaxies is old, with little ongoing star formation.

2. How are elliptical galaxies believed to have formed?

Answer: Elliptical galaxies are believed to have formed through mergers of smaller galaxies, resulting in a more random distribution of stellar orbits.

Observational Characteristics

3. What is the color of elliptical galaxies, and what does it indicate about their stars?

Answer: Elliptical galaxies appear reddish in color, indicating the presence of older, cooler stars.

4. How does the shape of elliptical galaxies vary, and what do the different classifications indicate?

Answer: The shape of elliptical galaxies ranges from nearly spherical (E0) to highly elongated (E7), with the classification indicating the degree of elongation.

Size and Mass

5. How do the sizes of elliptical galaxies vary, and what are the largest examples known as?

Answer: Elliptical galaxies can vary in size, from dwarf ellipticals to supergiant ellipticals, which can be among the largest galaxies in the universe.

6. What is the typical mass of elliptical galaxies compared to other galaxy types?

Answer: Elliptical galaxies are among the most massive galaxies in the universe.