Our Solar System
The structure of the Solar System - the Sun, the eight planets and the smaller bodies - and how gravity sets an object's weight and keeps everything in orbit.
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Our place in space 🌌
The **Solar System** is our corner of the Universe. At its centre is the **Sun**, a star, and orbiting it are **eight planets** (including the Earth), along with their moons and a swarm of smaller bodies. In this module you will learn what is in the Solar System, how gravity sets your **weight** on different worlds, and how gravity keeps the planets in **orbit**.
What is in the Solar System 🔑
The Sun is orbited by several kinds of body:
Order the planets 🪐
An interactive activity.
Match each body 🔗
- The Sun
- A natural satellite
- An asteroid
- A comet
- A star at the centre of the Solar System
- A moon that orbits a planet
- A small rocky body between Mars and Jupiter
- A small icy body on a long, stretched orbit
Nearest the Sun 🎯
Which planet orbits closest to the Sun?
- Mercury
- Earth
- Jupiter
- Neptune
Mass and weight ⚖️
These two words are often mixed up, but in physics they mean different things.
Weight on the Moon 🧮
An interactive activity.
Why you weigh less on the Moon 🌙
Your **mass** never changes, but your **weight** does, because it depends on the **gravitational field strength (g)** of the world you are on. On Earth g is about **10 N/kg**, but on the Moon it is only about **1.6 N/kg**, roughly a sixth as strong. So the same astronaut weighs about six times less on the Moon, even though they are made of exactly the same amount of matter.
Mass and weight ✅
Select the TWO statements that are true.
- An object has the same mass on the Moon as on Earth
- Weight is a force measured in newtons
- Weight is the same everywhere in the Solar System
- Mass is a type of force
The Solar System in words 🧱
At the centre of the Solar System is the _____, a giant ball of hot gas. Eight _____ orbit it, held in place by the force of _____. The planet closest to the Sun is _____. Small, icy bodies that travel on long, stretched orbits are called _____.
The changing model 🖍️
An interactive activity.
Gravity and orbits 🧭
An interactive activity.
Explain the difference ✍️
An interactive activity.