Galaxy vs. Universe: What's the Difference?
The difference is scale. A galaxy is one enormous group of stars, gas, and dust held together by gravity — our Milky Way is a single galaxy. The universe is everything: all the galaxies (hundreds of billions of them), plus all the space, time, matter, and energy that exists. A galaxy is a part; the universe is the whole.
See the difference, explained visually.
Watch a 2-minute animated lesson comparing galaxy and universe.
At a glance
| Galaxy | Universe | |
|---|---|---|
| What it is | One system of billions of stars | Everything that exists |
| Contains | Stars, planets, gas, dust | All galaxies, space, time, matter |
| How many | Hundreds of billions of them | One (by definition) |
| Our example | The Milky Way | The observable universe (~93 bn ly) |
| Scale | Thousands of light-years | Billions of light-years |
Which should you use?
Galaxy
You mean a galaxy when you're talking about one island of stars — the Milky Way, Andromeda, or any of the hundreds of billions of others.
Universe
You mean the universe when you're talking about everything — every galaxy and all of space and time together.
Frequently asked questions
- How many galaxies are in the universe?
- Hundreds of billions, possibly up to two trillion — each containing millions to trillions of stars. The universe contains all of them.
- Is the Milky Way the whole universe?
- No — the Milky Way is just our home galaxy, one of hundreds of billions in the universe.
- What's bigger than a galaxy?
- Galaxies cluster into groups and superclusters, which together form the large-scale structure of the universe — the biggest thing of all.