Lesson 2: Origin of the Solar System

Solar System Notes

Location: Milky Way Galaxy

Features:

• Large Scale:

  • Sun contains most of the Solar System’s mass

  • All planets orbit the Sun.

  • Most planets rotate clockwise (retrograde rotation).

• Small Scale:

  • Most planets rotate in the same direction as they orbit (prograde rotation)

Planet Type/Classification:

• Terrestrial Planets: (e.g., Mercury, Venus, Earth, Mars)

  • Solid, rocky surface

  • Made of rock and metal

  • Smaller, closer to the Sun

  • No rings

• Jovian Planets: (e.g., Jupiter, Saturn, Uranus, Neptune)

  • Gaseous surface

  • Low density, fluid interiors

  • Mostly of hydrogen, helium, ice

  • Thick atmosphere

  • Farther from the Sun

  • Have rings

Period of Revolution:

• 1 orbit around the Sun = 1 year (planet-specific)

• Moon's orbit around Earth = 1 month

Nebular Hypothesis: (Most accepted theory of solar system formation)

• Proposed by: Pierre Simon de Laplace (1796)

Stages of Nebular Hypothesis:

1. Nebula: Cloud of gas, dust, and rocks

2. Spinning Disk: Gravity pulls gas to the center → spins and flattens forms accretion disk

3. Protoplanets: Clumps form from dust and rock

4. Protostar: Gravity + pressure at the center forms the proto-Sun.

   More mass = more gravity and higher temperature.

Other Regions of the Solar System

• Asteroid Belt:

  • Between Mars and Jupiter

  • Leftover debris from a failed planet cuz of Jupiter's gravity

• Kuiper Belt:

  • Beyond Neptune

  • Contains icy bodies and dwarf planets

• Oort Cloud:

  • Huge, spherical region at the solar system’s edge

  • Contains icy bodies