Star vs. Planet: What's the Difference?
The key difference is light: a star makes its own, a planet doesn't. A star is a giant ball of gas that produces light and heat by nuclear fusion in its core. A planet is a smaller, cooler body that orbits a star and only shines by reflecting that star's light. The Sun is a star; Earth is a planet.
See the difference, explained visually.
Watch a 2-minute animated lesson comparing star and planet.
At a glance
| Star | Planet | |
|---|---|---|
| Makes its own light? | Yes — by nuclear fusion | No — reflects a star's light |
| What it is | Huge ball of glowing plasma | Rocky or gas body orbiting a star |
| Temperature | Thousands+ of degrees | Much cooler |
| Size | Enormous (Sun ≈ 1.4M km) | Far smaller |
| Moves | Stays put; things orbit it | Orbits a star |
Which should you use?
Star
It's a star when the object generates its own light and heat through fusion — like the Sun or the points of light in the night sky (each a distant sun).
Planet
It's a planet when the object orbits a star and shines only by reflected light — like Earth, Mars, or Jupiter orbiting our Sun.
Frequently asked questions
- Why do stars twinkle but planets don't?
- Stars are so far away they're essentially points of light, so our atmosphere bends it and makes them twinkle. Planets are closer and appear as tiny disks, which average out the twinkling.
- Is the Sun a star or a planet?
- The Sun is a star — it makes its own light and heat by fusion, and the planets (including Earth) orbit it.
- Can a planet become a star?
- No — a planet isn't massive enough. Stars need enough mass for gravity to ignite fusion; Jupiter would need to be about 80× heavier to become one.