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The solar system consists of the Sun, eight planets, and countless smaller bodies organized into distinct zones. The inner terrestrial planets (Mercury, Venus, Earth, Mars) are rocky and dense; the outer jovian planets are gas giants (Jupiter, Saturn) or ice giants (Uranus, Neptune). Between Mars and Jupiter lies the asteroid belt; beyond Neptune lies the Kuiper Belt of icy bodies, and further still the distant spherical Oort Cloud. All planetary orbits are nearly coplanar in the ecliptic plane, a consequence of the solar system's formation from a rotating disk.
Group planets by zone (terrestrial vs. jovian) and compare key properties: mass, radius, atmospheric composition, number of moons, and orbital period. Apply Kepler's third law to verify that orbital periods match semi-major axes for each planet.
You already know from Kepler's laws that planets orbit the Sun in ellipses with the Sun at one focus, and that orbital period increases with distance. From Newton's law of gravitation, you know the force holding these orbits together weakens with the square of the distance. The structure of the solar system is the physical result of these laws playing out across an enormous range of scales, from Mercury's tight 88-day orbit to Neptune's leisurely 165-year circuit.
The most fundamental organizational feature is the division between inner terrestrial planets and outer giant planets. Mercury, Venus, Earth, and Mars are small, rocky, dense, and close to the Sun. They have thin or negligible atmospheres (Earth being the exception with a moderate one), few or no moons, and no ring systems. Beyond the asteroid belt — a zone of rocky debris between Mars and Jupiter — the character of planets changes dramatically. Jupiter and Saturn are gas giants, composed mostly of hydrogen and helium, with masses hundreds of times that of Earth. Uranus and Neptune are ice giants, smaller than the gas giants and composed largely of water, ammonia, and methane ices along with hydrogen and helium. All four outer planets have extensive ring systems and numerous moons.
This inner-outer divide is not accidental. It reflects conditions during the solar system's formation: close to the young Sun, temperatures were too high for volatile compounds (water, methane, ammonia) to condense into solids. Only rock and metal could survive, so the inner planets formed from these refractory materials. Beyond the frost line (roughly between Mars and Jupiter), ices could condense, providing far more solid material for planetary cores to accumulate. These massive cores then gravitationally captured hydrogen and helium gas from the surrounding nebula, growing into giants. This is why applying Kepler's third law to the planets reveals not just a mathematical pattern, but a physical story: the orbital distances set the thermal environment, which determined what each planet could be made of.
Beyond the eight planets lie two additional reservoirs of small bodies. The Kuiper Belt, extending from about 30 to 55 AU, is a disk-shaped region of icy objects including Pluto, Eris, and many other dwarf planets. Much farther out, the Oort Cloud is a hypothesized spherical shell of icy bodies extending perhaps halfway to the nearest star, thought to be the source of long-period comets. The near-perfect coplanarity of planetary orbits — all lying close to the ecliptic plane — is itself evidence of formation from a single rotating disk of gas and dust, a prediction that follows directly from the conservation of angular momentum you encounter throughout physics.