5. Beyond the Milky Way: Galaxies and the Large-Scale Universe
GED® Science: Stars, Galaxies & the Universe · preview lesson
The Milky Way is just one of an estimated 2 trillion galaxies in the observable universe.
Types of galaxies:
| Type | Shape | Example |
|---|---|---|
| Spiral | Flat disk with curved arms | Milky Way, Andromeda |
| Barred spiral | Spiral with a central bar | Milky Way (our type) |
| Elliptical | Smooth, oval blob; range from spherical to elongated | M87 |
| Irregular | No regular shape | Magellanic Clouds |
Nearby galaxies:
- The Andromeda Galaxy (M31) is the closest large spiral galaxy to the Milky Way, about 2.5 million light-years away.
- The Large and Small Magellanic Clouds are irregular dwarf galaxies visible from the Southern Hemisphere, satellites of the Milky Way.
- The Milky Way and Andromeda belong to a small cluster called the Local Group, which contains about 50 galaxies.
Galaxy clusters and the cosmic web:
Galaxies are not scattered randomly. They group into clusters (dozens to thousands of galaxies) and superclusters (clusters of clusters). At the largest scales the universe looks like a cosmic web — a network of filaments of galaxies surrounding vast empty voids.
What type of galaxy is the Milky Way?
The Milky Way has spiral arms and a bar-shaped structure through its center, making it a barred spiral galaxy.
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