Elliptical galaxy

Definition

An elliptical galaxy is a type of galaxy characterized by its smooth, featureless light profile and an ellipsoidal shape, often containing older stars and little interstellar matter. These galaxies are typically more rounded than other types and can vary greatly in size, ranging from small dwarfs to massive giants. Their structure has implications for understanding the formation and evolution of galaxies within the broader context of the universe's structure.

5 Must Know Facts For Your Next Test

1. Elliptical galaxies are the most common type of galaxy in the universe, making up about 60% of all galaxies.
2. These galaxies generally have little to no ongoing star formation due to the scarcity of gas and dust, resulting in a population dominated by older stars.
3. Elliptical galaxies can be classified into different categories based on their shape, with 'E0' being nearly spherical and 'E7' being highly elongated.
4. They often reside in galaxy clusters and are believed to have formed through the merging of smaller galaxies over time.
5. The study of elliptical galaxies helps astronomers understand galactic evolution, as their characteristics differ significantly from those of spiral and irregular galaxies.

Review Questions

• How do elliptical galaxies differ from spiral and irregular galaxies in terms of structure and star formation?
  • Elliptical galaxies differ from spiral and irregular galaxies primarily in their smooth, featureless shapes and lack of significant star formation. While spiral galaxies have prominent arms filled with younger stars and interstellar gas, elliptical galaxies are dominated by older stars with little gas or dust present. Irregular galaxies, on the other hand, display chaotic shapes and actively form new stars. This difference in structure and composition plays a crucial role in understanding the lifecycle of galaxies within the universe.
• Discuss the significance of galaxy mergers in the formation of elliptical galaxies.
  • Galaxy mergers play a significant role in the formation of elliptical galaxies as they are thought to evolve from the collisions and interactions between smaller galaxies. When two or more galaxies merge, gravitational forces can strip away gas and dust while causing star populations to mix. The end result is an elliptical galaxy that exhibits a smoother light profile and a more homogeneous stellar population. This process helps explain the prevalence of elliptical galaxies in densely populated regions of the universe, such as galaxy clusters.
• Evaluate how studying elliptical galaxies contributes to our understanding of dark matter and cosmic evolution.
  • Studying elliptical galaxies offers valuable insights into dark matter distribution and cosmic evolution. These galaxies often contain vast amounts of dark matter, which influences their gravitational dynamics despite being less visible than other galaxy types. By analyzing the mass profiles and motions of stars within elliptical galaxies, astronomers can infer dark matter's presence and its role in galaxy formation. Understanding these relationships helps scientists piece together the larger narrative of how structures like galaxies evolved over billions of years in our expanding universe.

Related terms

Spiral Galaxy: A spiral galaxy features a flat, rotating disk containing stars, gas, and dust, along with a central concentration of stars known as a bulge, and is characterized by spiral arms.

Irregular Galaxy: An irregular galaxy lacks a distinct shape or structure, often containing young stars and large amounts of gas and dust, which contribute to their chaotic appearance.

Hubble's Tuning Fork: A morphological classification system for galaxies developed by Edwin Hubble, which categorizes galaxies into three main types: elliptical, spiral, and irregular.