The Solar System
Eight planets orbit the Sun along with moons, asteroids and comets.
About this topic
The Solar System formed about 4.6 billion years ago from a collapsing cloud of gas and dust. At its centre is the Sun, which holds 99.8% of the mass, and eight planets orbit it: four small rocky planets (Mercury, Venus, Earth, Mars) and four giants (Jupiter, Saturn, Uranus, Neptune).
Also orbiting are dwarf planets like Pluto, hundreds of moons, the asteroid belt between Mars and Jupiter, the Kuiper belt beyond Neptune and distant icy comets. All planets orbit in the same direction in nearly the same plane because of how the system formed.
Understanding the layout matters because every other topic in astronomy builds on it. Distances are enormous: if the Sun were a beach ball, Earth would be a pea about 30 metres away, and Neptune would be roughly a kilometre off. Scientists often use the astronomical unit (the Earth-Sun distance) to keep numbers manageable, so Jupiter sits at about 5.2 AU and Neptune at about 30 AU.
The shared direction and plane of the orbits is evidence for the nebular theory: the collapsing cloud spun faster as it shrank, flattened into a disc, and planets grew from clumps within it. This knowledge guides real work, from planning spacecraft trajectories to searching other star systems for similar layouts. A common misconception is that space is crowded; in truth the planets are tiny specks separated by vast emptiness. Another is that Pluto was demoted arbitrarily; it was reclassified in 2006 because it has not cleared its orbital neighbourhood.
Key ideas
- Inner rocky planets and outer giants
- Sun holds 99.8% of the mass
- Planets orbit in the same direction
Quick check
Use cases: where The Solar System helps
- Homework: review the key idea behind The Solar System before you start a problem set.
- Exam revision: use the quick check to test whether you can recall The Solar System without notes.
- Visual learning: play with the interactive lab to see how The Solar System changes when you adjust its inputs.
- Teaching a friend: explain The Solar System in your own words, then compare your version with the key ideas.
Earth science helps with weather forecasts, natural hazards, energy and climate planning.
Frequently asked questions
What is The Solar System?
Eight planets orbit the Sun along with moons, asteroids and comets.
What will I learn in The Solar System?
Inner rocky planets and outer giants. Sun holds 99.8% of the mass. Planets orbit in the same direction.
Is The Solar System part of Earth & Space?
Yes. It is one of 60 Earth & Space topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the The Solar System lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study The Solar System?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.