3. The Eight Planets
PrimaryThe Sun has eight planets circling around it, including our home, Earth. This chapter puts them in order and shows how they differ.
In order from the Sun
The eight planets, from closest to the Sun to farthest, are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. A popular way to remember the order is a sentence where each word starts with the same letter: "My Very Educated Mother Just Served Us Nachos."
The first four — Mercury, Venus, Earth, Mars — are smaller, rocky worlds called terrestrial planets. The next two, Jupiter and Saturn, are huge balls of gas called gas giants. The last two, Uranus and Neptune, are big and cold, made mostly of icy materials, called ice giants.
| Planet | Kind | Moons |
|---|---|---|
| Mercury | Rocky | 0 |
| Venus | Rocky | 0 |
| Earth | Rocky | 1 |
| Mars | Rocky | 2 |
| Jupiter | Gas giant | 95 |
| Saturn | Gas giant | 146 |
| Uranus | Ice giant | 28 |
| Neptune | Ice giant | 16 |
Terrestrial planets
- Mercury, Venus, Earth, Mars
- Small, dense, rocky surfaces
- Close to the Sun's warmth
- Few or no moons; thin or no atmosphere
Gas & ice giants
- Jupiter, Saturn, Uranus, Neptune
- Huge, low-density balls of gas and ice
- Far out, beyond the frost line
- Dozens of moons; rings; deep atmospheres
Why order and size matter
The order tells you how the planets formed: rocky, small worlds close to the Sun's heat, and gigantic gassy and icy worlds farther out where it's cold enough for ices to gather. Try the Universe Explorer above — click each planet as it orbits and compare their real sizes and distances for yourself!
Hands-on: build the planet order
Write the first letter of each planet on eight separate cards: M, V, E, M, J, S, U, N.
- Shuffle the cards.
- Using the memory sentence "My Very Educated Mother Just Served Us Nachos," put the cards back in the correct order.
- Say each planet's full name as you place its card.
- Time yourself — can you do it faster the second try?
Answer: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
Test your understanding
Which planet is closest to the Sun?
Mercury — it is first in line, orbiting fastest and closest of all eight planets.
Which is the biggest planet?
Jupiter, by far. It is a gas giant so large that every other planet in the Solar System could almost fit inside it combined.
Name the four rocky (terrestrial) planets.
Mercury, Venus, Earth, and Mars — the four closest to the Sun, all with solid, rocky surfaces you could (in theory) stand on.
Is Pluto one of the eight planets?
No. Pluto used to be called a planet, but in 2006 astronomers reclassified it as a dwarf planet because it hasn't cleared other objects out of its orbital path. It's still an important, fascinating world — just in a different category (more in Chapter 8).
How the ideas connect
Every key idea in this chapter, branching from the core concept — use it to see the whole picture at a glance.
The key facts, visualised
Worked problems, step by step
Follow each solution line by line, then try to reproduce it on paper before moving on.
Example 1List the planets in order from the Sun.
- Start closest to the Sun
- Use the letters M V E M J S U N
Example 2Which planet is third from the Sun?
- Count: Mercury 1, Venus 2, Earth 3
Now you try
Work each one out first, then tap to reveal the worked answer.