The Solar System - AQA GCSE Physics Revision Notes

Key Elements of the Solar System

• Sun
  • Center of the Solar System; a star that makes up over 99% of the Solar System's mass.
• Planets
  • Eight planets orbit the Sun.
  • Two categories:
    • Rocky planets: Mercury, Venus, Earth, Mars.
    • Gas planets: Jupiter, Saturn, Uranus, Neptune.
• Dwarf Planets
  • Have weak gravitational fields; do not clear their orbits of other debris.
• Moons
  • Natural satellites that orbit the planets.
• Artificial Satellites
  • Man-made objects orbiting other objects in space (e.g., ISS).
• Asteroids and Comets
  • Asteroids: rocky objects, primarily found in the asteroid belt between Mars and Jupiter.
  • Comets: composed of dust and ice, have elliptical orbits, develop tails when near the Sun.

Our Place in Space

• Solar system is part of the Milky Way galaxy.
• Universe comprises multiple galaxies with billions of stars.

Distances in the Solar System

• Outer regions of the solar system are about (5 \times 10^{12}) meters from the Sun.
• Light from the Sun takes about 8 minutes to reach Earth.
• Speed of light is a constant (3 \times 10^8) meters per second.

Example Calculation

• Radius of Mercury's orbit: (5.8 \times 10^9) meters.
• Time taken for light to reach Mercury:
  • Equation: ( \text{Time} = \frac{\text{Distance}}{\text{Speed}} )
  • Calculation: ( \frac{5.8 \times 10^9}{3.0 \times 10^8} = 19.3 ) seconds.

Additional Information

• Mnemonic for planet order: My Very Excellent Mother Just Served Us Noodles (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune).
• Previously used Nine Pizzas when Pluto was included as a planet.
• Light from the nearest star (other than the Sun) takes 4 years to reach Earth.