Elliptical galaxies

Definition

Elliptical galaxies are a type of galaxy characterized by their smooth, featureless light profiles and ellipsoidal shapes. They range from nearly spherical to elongated forms and typically contain older, red stars with little gas or dust, indicating a low rate of star formation. Their structure and composition can offer insights into the chemical evolution of galaxies over time.

5 Must Know Facts For Your Next Test

1. Elliptical galaxies can be classified into various types based on their shapes, ranging from E0 (almost spherical) to E7 (highly elongated).
2. These galaxies often contain very little interstellar matter, which means they have minimal ongoing star formation compared to spiral galaxies.
3. The older stellar populations found in elliptical galaxies indicate that they formed early in the universe's history and have not experienced significant star formation for billions of years.
4. Elliptical galaxies can grow in size and mass through the process of galactic mergers, allowing them to acquire new stars and possibly gas, though they still remain low in star formation activity.
5. The study of elliptical galaxies helps astronomers understand the processes that govern galaxy evolution and the overall chemical enrichment of the universe.

Review Questions

• How do elliptical galaxies differ from spiral galaxies in terms of structure and star formation?
  • Elliptical galaxies differ from spiral galaxies primarily in their structure; while elliptical galaxies have smooth, featureless profiles and lack prominent features like spiral arms, spiral galaxies have flat disks with well-defined arms. Additionally, elliptical galaxies contain mostly older stars and exhibit very little interstellar gas and dust, resulting in low star formation rates. In contrast, spiral galaxies are rich in gas and dust, allowing for ongoing star formation and the presence of younger stars.
• Discuss the significance of galactic mergers in the evolution of elliptical galaxies.
  • Galactic mergers play a significant role in the evolution of elliptical galaxies by allowing them to increase their mass and size. When two or more galaxies collide, the resulting interactions can lead to the reshaping of their structures and the merging of stellar populations. This process can also result in bursts of star formation if sufficient gas is available during the merger. Consequently, studying these mergers helps astronomers understand how elliptical galaxies form and evolve over cosmic time.
• Evaluate the role of elliptical galaxies in understanding the chemical evolution of the universe.
  • Elliptical galaxies are key to evaluating the chemical evolution of the universe because they provide insight into how different generations of stars contribute to chemical enrichment over time. The older stellar populations within these galaxies indicate that they formed early in cosmic history, capturing a snapshot of the universe's conditions at that time. By analyzing the stellar populations and chemical compositions found in elliptical galaxies, astronomers can infer processes such as supernova nucleosynthesis and the recycling of materials through various galactic events, enriching our understanding of galaxy formation and evolution.

Related terms

spiral galaxies:

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

star formation:

The process by which dense regions within molecular clouds collapse under their own gravity to form new stars, playing a crucial role in galaxy evolution.

galactic mergers: Events where two or more galaxies collide and combine, significantly affecting their structure, star formation rates, and overall chemical makeup.