Slides
Lesson slides
Slides for the lesson
Open resourceLesson 02
The Solar System
Describe the Solar System, compare its main bodies, and use gravity and data to explain planetary motion.
Objectives
Lesson outcomes
- Describe the Solar System as the Sun, eight planets in order, minor planets, moons, asteroids, and comets.
- Compare the inner and outer planets and explain the difference using the accretion model of Solar System formation.
- Explain why planets orbit the Sun and describe how gravitational field strength and orbital speed change with distance from the Sun.
- Analyse simple planetary data and calculate light-travel time across significant Solar System distances.
Syllabus
CIE 0625 syllabus points
10 linked
- 6.1.2.1 Describe the Solar System as containing: (a) one star, the Sun (b) the eight named planets and know their order from the Sun (c) minor planets that orbit the Sun, including dwarf planets such as Pluto and asteroids in the asteroid belt (d) moons, that orbit the planets (e) smaller Solar System bodies, including comets and natural satellites
- 6.1.2.2 Know that, in comparison to each other, the four planets nearest the Sun are rocky and small and the four planets furthest from the Sun are gaseous and large, and explain this difference by referring to an accretion model for Solar System formation, to include: (a) the model’s dependence on gravity (b) the presence of many elements in interstellar clouds of gas and dust (c) the rotation of material in the cloud and the formation of an accretion disc
- 6.1.2.3 Know that the strength of the gravitational field (a) at the surface of a planet depends on the mass of the planet (b) around a planet decreases as the distance from the planet increases
- 6.1.2.4 Calculate the time it takes light to travel a significant distance such as between objects in the Solar System
- 6.1.2.5 Know that the Sun contains most of the mass of the Solar System and this explains why the planets orbit the Sun
- 6.1.2.6 Know that the force that keeps an object in orbit around the Sun is the gravitational attraction of the Sun
- 6.1.2.7 Know that planets, minor planets and comets have elliptical orbits, and recall that the Sun is not at the centre of the elliptical orbit, except when the orbit is approximately circular
- 6.1.2.8 Analyse and interpret planetary data about orbital distance, orbital duration, density, surface temperature and uniform gravitational field strength at the planet’s surface
- 6.1.2.9 Know that the strength of the Sun’s gravitational field decreases and that the orbital speeds of the planets decrease as the distance from the Sun increases
- 6.1.2.10 Know that an object in an elliptical orbit travels faster when closer to the Sun and explain this using the conservation of energy
Lesson Notes
Student guidance and lesson notes
Overview
This lesson is mainly about structure and comparison. You need a clear map of the Solar System, but they also need the physical reasons behind the patterns, especially why the inner planets differ from the outer planets and why orbital behaviour changes with distance from the Sun.
What You Need to Know
- Organise the Solar System around the Sun first, then place the eight planets in order before adding dwarf planets, asteroids, comets, and moons.
- Compare the rocky inner planets with the larger gaseous outer planets and link this pattern to the accretion model and temperature conditions in the early Solar System.
- Remember that the Sun contains most of the mass in the Solar System, so its gravity provides the force that keeps planets in orbit.
- Show that gravitational field strength decreases with distance from a planet or the Sun, and link this to lower orbital speeds for more distant planets.
- Include elliptical orbits and the idea that objects travel faster when nearer the Sun because of energy conservation.
How to Work Through It
- Start with a retrieval task where you place the planets in order and classify a few Solar System objects.
- Build a comparison table for inner and outer planets, then work through the accretion-model explanation for the pattern.
- Use diagrams and data to connect orbit size, orbital duration, gravitational field strength, and orbital speed.
- Finish with a short light-travel-time calculation and one interpretation task using planetary data.
Check Your Understanding
- Check whether you can decide whether a named object is a planet, minor planet, moon, asteroid, or comet.
- Use a hinge question where you choose which planet group is rocky and explain why.
- Try one orbital-data question that asks which planet should move faster and why.
Common Mistakes
- Treating Pluto as one of the eight planets. Keep the category of dwarf planet explicit.
- Some think the outer planets move faster because their orbits are larger. Go back to the decrease in the Sun’s gravitational field strength with distance.
- You may say the Sun is at the centre of every elliptical orbit. Clarify that it lies at a focus, and only nearly circular orbits look centred.
Next Steps
- Set a comparison grid or retrieval quiz so the structure of the Solar System becomes secure.
- Carry forward the ideas of stars, galaxies, and astronomical distances into the next lesson.
Lesson Resources
Materials for this lesson
Use these videos, slide decks, documents, or links to work through the lesson.