Regularities of the Solar System
- Rather than orbiting the Sun randomly, the motions of the
planets are rather organized.
- All objects orbit in the same plane.
- All orbits are nearly circular.
- All planets orbit the Sun in the same direction.
- Most planets rotate in the same sense as they orbit.
- Regular satellites of the Major Planets form mini-solar systems
- Satellites also orbit their planets in the common direction of the planetary spins and orbits.
- Planets also appear to be sorted by composition and size.
- Planets: Small rocky planets (terrestrial) near the Sun.
Large gassy planets (Jovian) far away.
- Solid objects in general: Rocky inner planets vs. icy outer moons.
- Exposed planetary surfaces are all heavily cratered
- These regular motions and features are fossil evidence of the processes
which formed the Solar System.
- They imply that the planets formed from a flattened disk of dust
and gas. The system of planets is a relic of the disk from which they formed retaining some ``memory" of the structure and rotation of the disk.
Revised October 18, 2000