Britannica
Sources used in this answer
How does angular momentum affect whether a protogalaxy becomes a spiral or elliptical galaxy?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
Galaxy
The Whirlpool Galaxy (left), also known as M51, an Sc galaxy accompanied by a small irregular companion galaxy, NGC 5195 (right).
In the study of galaxy formation, the angular momentum of the original gas clouds, or protogalaxies, is a primary factor in determining the final shape of the galaxy.1
- Spiral Galaxies: A protogalaxy possessing a large amount of angular momentum tends to collapse into a flat, rapidly rotating system, resulting in a spiral galaxy.1
- Elliptical Galaxies: A protogalaxy with very little angular momentum develops into a more nearly spherical system, forming an elliptical galaxy.1
While this relationship between angular momentum and galactic structure was a central concept in 20th-century models of galaxy formation, modern astronomy has also established that collisions and the accretion of smaller galaxies play a significant role in shaping the structure and appearance of galaxies throughout their evolution.1