planetary system
The Solar System
The Sun's family: eight planets, lots of moons, belts full of leftover rubble, comets on long journeys -- and a few spacecraft we sent out to explore it all.
What it is
The Sun and everything that belongs to it: eight planets, their moons, two belts of leftovers, a swarm of comets, and a handful of machines we sent out ourselves.
Planetary system: A star known to have worlds around it. Every kind of thing there is →
Can you see it?
Not as one thing, no — the Solar System is a place rather than a sight, and you are already inside it. What you go out and look at are the things in it, one at a time.
Worth knowing about the Solar System
- The Sun
- Not just the biggest thing here -- it practically IS the solar system: 998 parts in every 1,000 of all the material. Everything else on this list adds up to the last little sliver, and every bit of it orbits the Sun.
- The planets
- Eight, in two families. Four small rocky worlds near the warmth -- Mercury, Venus, Earth, Mars -- then four giants further out -- Jupiter, Saturn, Uranus, Neptune -- balls of gas and ice with no ground to stand on.
- Moons
- A planet can have companions of its own. Earth has one large Moon; Jupiter and Saturn have whole families; and even the asteroid Didymos owns a tiny moon, Dimorphos. Whatever a thing orbits, that is where you will find it in this list.
- The belts
- Two rings of leftovers from when the planets were built: the rocky asteroid belt between Mars and Jupiter, and the icy Kuiper belt beyond Neptune, where Pluto and the other dwarf planets live. Far beyond both, a thin shell of sleeping comets -- the Oort cloud -- marks the true edge of the Sun's neighbourhood.
- Comets
- Icy wanderers on long, stretched orbits. Each visit close to the Sun boils away a little of their ice into the glowing tail that makes them famous -- Halley's returns about once a human lifetime.
- Visitors and messengers
- Once in a while something falls through from another star entirely -- 'Oumuamua and Borisov were only passing, and never belonged to the Sun. And two machines of our own, Voyager 1 and 2, have now done the same journey in reverse: they have left the Sun's neighbourhood for good, carrying golden records out among the stars.
Where it sits
Orion spur of the Milky Way, 26,000 light-years from the galactic centre
Then go outside
Too big to look at all at once — but the things inside it are not. The Planetarium will show you which are up.
