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A galaxy is a huge collection of stars, stellar remnants, gas, dust and dark matter held together by gravity. Our [[The Solar System|Solar System]] lies inside a barred spiral galaxy, teh Milky Way.
## Types
Edwin Hubble sorted galaxies by shape in the 1920s, and his scheme is still in use.
- **Spiral** galaxies have rotating discs with winding arms.
- **Elliptical** galaxies are smooth and contain mostly older stars.
- **Irregular** galaxies have no clear form.
## Scale
Galaxies range from dwarfs with a few million stars to giants with trillions. Most large galaxies appear to have a supermassive black hole at their centre.