Galaxy
- Galaxy is a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction. They are the major building blocks of the universe.
- The 13.8-billion-year-old universe hosts various galaxy types, including spiral, elliptical, and those with or without bulges. Younger galaxies tend to be spiral, while older ones have various shapes.
- Astronomers study galaxies to understand their formation and evolution, but older galaxies are harder to study due to their fainter light.
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