Science
What is The solar system?
The solar system is the Sun and everything bound to it by gravity — eight planets, their moons, dwarf planets, asteroids, and comets. It formed about 4.6 billion years ago from a collapsing cloud of gas and dust.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains the solar system.
Key things to understand
- 1The Sun holds over 99% of the system's mass and anchors everything in orbit.
- 2The four inner planets are rocky; the four outer ones are gas and ice giants.
- 3Smaller bodies — asteroids, comets, dwarf planets like Pluto — orbit too.
- 4Gravity keeps every object circling the Sun.
Frequently asked questions
- How many planets are in the solar system?
- Eight: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
- Why isn't Pluto a planet?
- In 2006 it was reclassified as a 'dwarf planet' because it hasn't cleared other objects from its orbital path.
- What holds the solar system together?
- The Sun's gravity, which keeps all the planets and smaller bodies in orbit.