Architecture of the Solar System
As to the question of how the Solar System began, there are roughly two categories of theories that have been proposed to explain that event. One such category of theories is those theories that invoke an accidental catastrophic event, such as the near collision between the Sun and a star, while the other category of theories is those theories that involve a natural, non-catastrophic event, such as might occur in conjunction with the birth of star. A historical approach to the explanations of planetary genesis is a good beginning, but first we should summarize the major characteristics of the Solar System for which any theory of origin should account (Garber, Brush, Everitt).
A sequence of natural forces evidently created and shaped the Solar System somewhat along the lines revealed by the following clues, which suggest that the design most likely possessed continuity in its processes and did not materialize through a sequence of unrelated, random events:
- The planets are isolated from each other without bunching, and they are placed at orderly intervals.
- The planets' orbits are nearly circular, except for those of Mercury and Pluto.
- Their orbits are nearly in the same plane; Mercury and Pluto are again exceptions.
- All the planets and asteroids revolve around the Sun in the same direction that the Sun rotates (from west to east).
- Except for Venus, Uranus, and Pluto, the planets also rotate around their axes from west to east (Garber, Brush, Everitt).
A planet's system of satellites can be divided into either a regular system with direct orbits approximately in the planet's equatorial plane or an irregular system with irregular orbits inclined at various angles. The Terrestrial planets have high mean densities and relatively thin or no atmospheres, rotate slowly, and possess few or no satellites--points that are undoubtedly related to their smallness and closeness to the Sun.......
