Four object types — and what each orbits
The Solar System holds exactly four kinds of object. The Sun — one star, at the centre, orbiting nothing. Eight planets, which orbit the Sun. Minor planets — dwarf planets such as Pluto, and asteroids, most of them in the asteroid belt — which also orbit the Sun. And moons (natural satellites), which orbit the planets. Mercury and Venus have no moons, Earth has one, and the giant outer planets have many.
Planet order: Mercury to Neptune
Learn the eight in order outward from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Mnemonic: My Very Easy Method Just Speeds Up Naming. The asteroid belt splits the list 4-and-4, sitting between Mars (4th) and Jupiter (5th): the four inside it are the inner planets, the four beyond it the outer planets. The list ends at Neptune.
Minor planets — dwarf planets and asteroids
A planet is a large body orbiting the Sun (there are eight). A dwarf planet — for example Pluto, and Ceres in the asteroid belt — also orbits the Sun but is a minor planet. An asteroid is a small rocky body orbiting the Sun, most lying in the belt. Dwarf planets and asteroids are grouped as minor planets because they orbit the Sun yet are far smaller than the eight. A moon orbits a planet.
Drawn from real examiner reports.
Pluto is not the ninth planet
The Solar System has eight planets and the list ends at Neptune. Pluto orbits the Sun but lies far beyond Neptune and is much smaller, so it is a dwarf planet — a minor planet, not one of the eight. If a question asks for the planets in order from the Sun, stop at Neptune; adding Pluto is a marked error.
Dwarf planet is not an asteroid
Both are minor planets, but they are not the same thing. An asteroid is a small rocky body, and most sit in the asteroid belt between Mars and Jupiter. A dwarf planet is a larger minor planet — Pluto beyond Neptune, Ceres inside the belt. Calling Pluto an asteroid, or claiming every minor planet lives in the belt, loses the classification mark.
Moons orbit planets, not the Sun
Moons orbit planets. The Moon orbits the Earth, not the Sun directly. The objects that orbit the Sun are the planets, the dwarf planets and the asteroids. In a sketch, a moon drawn on its own orbit around the Sun loses the mark; in writing, "a moon goes round the Sun" scores zero.
The Sun is a star, not a planet
The Sun is a star — the only star in the Solar System — and it sits at the centre, orbiting nothing. It is not a planet and not "a very big planet". Everything else orbits it, either directly (planets, dwarf planets, asteroids) or by way of a planet (moons). Say "star" explicitly; "the Sun" alone often will not earn the mark.
The belt sits between Mars and Jupiter
The asteroid belt lies between Mars and Jupiter — between the 4th and 5th planets. The two usual wrong placements are between Earth and Mars, and out beyond Neptune. Fixing the belt in the right gap also fixes the inner/outer split: four planets inside the belt, four beyond it.
Uranus/Neptune and Earth/Mars swaps
Order slips throw away easy recall marks. The pairs most often swapped are Uranus and Neptune (Uranus 7th, Neptune 8th) and Earth and Mars (Earth 3rd, Mars 4th). Run the mnemonic — My Very Easy Method Just Speeds Up Naming — before you write, then check the belt still splits the list 4-and-4.
Match points to the mark tariff
Give one distinct point per mark. A 2-mark "describe the Solar System" wants two separate ideas, a 4-mark question four — restating "things orbit the Sun" in different words earns nothing extra. Count your points against the tariff before moving on.
State vs describe vs name
State wants a one-line fact (name the 5th planet: Jupiter). Describe wants the contents listed, each with what it orbits. Name wants the object only, with no explanation. Answering a "describe" with a bare list, or a "state" with a paragraph, both throw marks away.
Always say what orbits what
The most reliable sentence to include: the planets, dwarf planets and asteroids orbit the Sun, while moons orbit the planets. Naming an object without saying what it orbits is the usual way a "describe the Solar System" answer quietly drops marks.
Solar System sketch: five checks
Before handing in a Solar System sketch, check five things: Sun at the centre and labelled a star; eight planets in the right order; the belt between Mars and Jupiter; a moon on an orbit round a planet; and Pluto, if shown, beyond Neptune and labelled a dwarf planet.
Cambridge 0654 spec reference: Section P6 "Space physics", sub-topic P6.1 (Core only). This leaf is descriptive: you must be able to describe the Solar System as containing one star (the Sun), the eight named planets in order, minor planets (dwarf planets such as Pluto, and asteroids in the asteroid belt) and moons that orbit the planets.
Scope note: gravity and orbits, orbital-speed calculations, nuclear fusion in the Sun, star life cycles, light-years and the Big Bang are covered in other P6 leaves and are not part of P6.1.
This is a descriptive Core topic -- there are no equations to learn for P6.1. Instead, the "formula" to memorise is the ordered list of objects:
with dwarf planets (e.g. Pluto) orbiting the Sun beyond Neptune, and moons orbiting the planets.
(Core) What is the Sun, and what is its position in the Solar System?
The Solar System has 8 planets. The 4 planets closer to the Sun than the asteroid belt (Mercury, Venus, Earth, Mars) are called the inner planets.
Work out how many planets lie beyond the asteroid belt (the outer planets). (1 mark)
