Spiral galaxies
from class:
Intro to Astronomy
Definition
Spiral galaxies are a type of galaxy characterized by their flat, disk-like shape with spiral arms winding outward from the center. They contain a mix of young and old stars, gas, and dust, making them sites of active star formation.
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5 Must Know Facts For Your Next Test
- Spiral galaxies are categorized into three main types: Sa, Sb, and Sc based on the tightness of their spiral arms and the size of their central bulge.
- The Milky Way is an example of a barred spiral galaxy, classified as SBbc.
- Spiral arms are regions with higher concentrations of gas and young stars due to ongoing star formation.
- These galaxies often have supermassive black holes at their centers.
- They make up about 60-70% of all observed galaxies in the universe.
Review Questions
- What distinguishes a spiral galaxy from other types of galaxies?
- How do astronomers classify different types of spiral galaxies?
- Why are the spiral arms important regions within these galaxies?
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