Elliptical galaxy

Definition

An elliptical galaxy is a type of galaxy characterized by its smooth, featureless light distribution and an ellipsoidal shape. These galaxies vary in size and can be found in a range of luminosities, typically containing older stars with little to no ongoing star formation. Their structure and composition highlight significant aspects of galaxy classification and the properties of various galactic types.

5 Must Know Facts For Your Next Test

1. Elliptical galaxies make up about 10-15% of the total number of galaxies in the universe, but they can account for around half of the total galactic mass.
2. These galaxies lack the prominent features seen in spiral galaxies, such as dust lanes and young star populations, primarily hosting older stars.
3. Elliptical galaxies are generally divided into two categories: 'regular' ellipticals that exhibit smooth light profiles and 'dwarf' ellipticals that are smaller and less luminous.
4. The formation of elliptical galaxies is often linked to galactic mergers, where the interaction between two or more galaxies leads to their coalescence into a single elliptical structure.
5. Elliptical galaxies often reside in clusters, where gravitational interactions and mergers are more likely to occur due to the high density of nearby galaxies.

Review Questions

• What are the key characteristics that differentiate elliptical galaxies from spiral galaxies?
  • Elliptical galaxies are characterized by their smooth, featureless light distribution and generally elliptical shape, while spiral galaxies have distinct features such as spiral arms and central bulges. In terms of star composition, elliptical galaxies predominantly contain older stars with little to no new star formation, whereas spiral galaxies actively form new stars from their abundant gas and dust. These differences reflect the varying evolutionary paths these types of galaxies have undergone.
• Discuss the role of galactic mergers in the formation of elliptical galaxies.
  • Galactic mergers play a crucial role in the formation of elliptical galaxies. When two or more galaxies collide and merge, their gravitational forces cause them to lose their original shapes and settle into a more homogeneous structure typical of ellipticals. This process not only leads to the redistribution of stars but also suppresses star formation due to the depletion of gas resources. As a result, the newly formed elliptical galaxy often contains older stellar populations and lacks the distinct features seen in spiral counterparts.
• Evaluate the significance of elliptical galaxies in understanding galaxy evolution and cosmic structures.
  • Elliptical galaxies provide valuable insights into galaxy evolution and the dynamics of cosmic structures. Their prevalence in dense environments like clusters suggests that interactions between galaxies are significant drivers of evolution. Studying their formation through mergers helps astronomers comprehend how mass and structure build over time. Additionally, analyzing their properties contributes to our understanding of dark matter distribution and the overall lifecycle of matter in the universe, ultimately enhancing our grasp of how different types of galaxies interact within cosmic frameworks.

Related terms

spiral galaxy:

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

lenticular galaxy: A lenticular galaxy is an intermediate type between elliptical and spiral galaxies, characterized by a central bulge and a disk but lacking significant spiral arms.

Hubble classification: The Hubble classification system is a morphological classification scheme for galaxies that categorizes them into several types, including elliptical, spiral, and irregular galaxies.