Elliptical galaxy

Definition

An elliptical galaxy is a type of galaxy characterized by its smooth, featureless light profile and an ellipsoidal shape. These galaxies generally contain older stars and minimal amounts of gas and dust, leading to little ongoing star formation. Understanding elliptical galaxies is important in the study of galaxy classification and in the development of theories about galaxy formation and evolution.

5 Must Know Facts For Your Next Test

1. Elliptical galaxies are divided into classes based on their elongation, ranging from nearly spherical (E0) to highly elongated (E7).
2. They typically lack the well-defined structure seen in spiral galaxies and usually have very little interstellar gas, making them less conducive to new star formation.
3. The majority of stars in elliptical galaxies are older, which gives them a redder appearance compared to younger, bluer stars in spiral galaxies.
4. Elliptical galaxies can vary significantly in size, with some being dwarf galaxies containing only a few billion stars, while others can be giant galaxies housing trillions of stars.
5. These galaxies are often found in dense environments such as galaxy clusters, where they can merge with other galaxies, leading to the formation of larger elliptical galaxies.

Review Questions

• How do the characteristics of elliptical galaxies compare to those of spiral galaxies?
  • Elliptical galaxies are generally smoother and more featureless than spiral galaxies, which have well-defined structures like arms and a central bulge. While elliptical galaxies mostly consist of older stars and contain very little gas and dust for new star formation, spiral galaxies have younger stars and ongoing star formation due to their abundant interstellar material. This fundamental difference in composition and structure highlights the diversity found within the universe's galaxy types.
• What role do elliptical galaxies play in our understanding of galaxy formation and evolution?
  • Elliptical galaxies provide critical insights into the processes of galaxy formation and evolution. Their characteristics suggest that they often formed through the merging of smaller galaxies, which can explain their lack of structure and older stellar populations. Studying these galaxies helps astronomers understand the effects of gravitational interactions in dense environments like galaxy clusters, shedding light on how different types of galaxies evolve over time.
• Evaluate the significance of the Hubble Sequence in classifying elliptical galaxies and how it enhances our comprehension of galactic evolution.
  • The Hubble Sequence is significant as it provides a systematic framework for classifying various galaxy types, including elliptical ones. By categorizing elliptical galaxies based on their shape and size, it allows astronomers to analyze their properties systematically. This classification aids in understanding how environmental factors influence galactic evolution and helps identify the processes behind galaxy mergers and interactions that lead to the formation of different galaxy types.

Related terms

Spiral Galaxy: A spiral galaxy is a type of galaxy that has a flat, rotating disk containing stars, gas, and dust, along with a central concentration of stars known as the bulge.

Galaxy Cluster: A galaxy cluster is a structure that consists of a group of galaxies held together by gravity, often containing hundreds or thousands of galaxies.

Hubble Sequence:

The Hubble Sequence is a classification scheme for galaxies proposed by Edwin Hubble, which categorizes galaxies into different types, including spiral, elliptical, and irregular.