Elliptical galaxies

Definition

Elliptical galaxies are a type of galaxy characterized by their ellipsoidal shape, smooth light distribution, and lack of significant structure. These galaxies primarily contain older stars and very little gas or dust, leading to minimal new star formation. Their simplicity in structure and stellar population makes them an essential component in the broader understanding of the universe and its constituents.

5 Must Know Facts For Your Next Test

1. Elliptical galaxies are classified from E0 to E7 based on their elongation, where E0 is nearly spherical and E7 is highly elongated.
2. They are often found in dense regions of the universe like galaxy clusters, where gravitational interactions play a role in their formation.
3. Elliptical galaxies typically lack the gas and dust needed for star formation, which results in older stellar populations and a reddish color due to the dominance of older stars.
4. These galaxies make up about 10-15% of all known galaxies in the universe but contain a significant portion of the universe's total stellar mass.
5. Some elliptical galaxies can be very massive, with supermassive black holes at their centers that can significantly affect their dynamics and evolution.

Review Questions

• How do elliptical galaxies differ from spiral galaxies in terms of structure and stellar population?
  • Elliptical galaxies differ significantly from spiral galaxies primarily in their structure and stellar population. While spiral galaxies have a flat disk structure with well-defined arms and actively forming stars due to abundant gas and dust, elliptical galaxies possess a smooth, ellipsoidal shape with little to no structure. Ellipticals are mainly composed of older stars with minimal new star formation, resulting from their lack of gas and dust.
• Discuss the role of gravitational interactions in the formation and location of elliptical galaxies within galaxy clusters.
  • Gravitational interactions play a crucial role in both the formation and location of elliptical galaxies within galaxy clusters. In dense environments, like clusters, interactions between galaxies can lead to mergers, which often result in the formation of elliptical galaxies. This process can strip gas from merging galaxies, reducing star formation activity and leading to an older stellar population typical of ellipticals.
• Evaluate the implications of studying elliptical galaxies on our understanding of galaxy evolution and the overall structure of the universe.
  • Studying elliptical galaxies provides valuable insights into galaxy evolution and the large-scale structure of the universe. Their characteristics reflect different evolutionary paths compared to spiral galaxies, highlighting processes like mergers and interactions. By examining how ellipticals form and evolve within clusters, astronomers can better understand cosmic dynamics, dark matter distribution, and the history of star formation across various environments in the universe.

Related terms

spiral galaxies: Spiral galaxies are galaxies with a flat, rotating disk containing stars, gas, and dust, as well as a central concentration of stars known as the bulge. They exhibit well-defined spiral arms that arise from the density wave theory.

galaxy clusters: Galaxy clusters are large-scale structures that consist of hundreds to thousands of galaxies bound together by gravity. They serve as significant markers for understanding the large-scale structure of the universe.

Hubble classification: The Hubble classification is a system used to categorize galaxies based on their shapes and structures. It includes categories such as spiral, elliptical, and irregular galaxies.