Solar System vs. Galaxy: What's the Difference?
It's a matter of scale, and they're nested. A solar system is a single star plus everything orbiting it — for us, the Sun and its eight planets. A galaxy is hundreds of billions of stars, many with their own solar systems, all bound by gravity. Our solar system is just one tiny speck within the Milky Way galaxy.
See the difference, explained visually.
Watch a 2-minute animated lesson comparing solar system and galaxy.
At a glance
| Solar System | Galaxy | |
|---|---|---|
| Centred on | One star (our Sun) | Billions of stars; a central black hole |
| Contains | A star + its planets, moons, comets | Billions of stars & their systems |
| Size | Up to ~2 light-years across | Tens of thousands of light-years |
| How many stars | One | Hundreds of billions |
| Relationship | Sits inside a galaxy | Holds countless solar systems |
Which should you use?
Solar System
You mean a solar system when you're talking about one star and the worlds orbiting it — like the Sun, Earth, and the other planets.
Galaxy
You mean a galaxy when you're talking about the vast collection of billions of stars — and their solar systems — like the Milky Way.
Frequently asked questions
- Is the solar system inside the galaxy?
- Yes — our solar system is one of hundreds of billions of star systems inside the Milky Way galaxy, about two-thirds of the way out from the centre.
- How many solar systems are in a galaxy?
- Potentially hundreds of billions — roughly as many as there are stars, since most stars can host planets of their own.
- What's bigger, a galaxy or a solar system?
- A galaxy is vastly bigger — it contains billions of solar systems and spans tens of thousands of light-years, while a solar system is a tiny part of it.