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The Solar System

Our solar family

Orbits and tilts of the planets

Chemical condensation sequence in the solar nebula

Mass of Members

ObjectPercentage of Total Mass of Solar System
Sun99.80%
Jupiter0.10%
Cometsapprox. 0.0005-0.03%
All other planets and dwarf planets0.04%
Moons and rings0.00005%
Asteroidsapprox. 0.000002%
Cosmic dustapprox. 0.0000001%

Characteristics

  • Orderly motion
    • Nearly circular orbits in the same plane
    • Everything is moving counter clockwise
    • Almost all spinning counter clockwise
  • Asteroids and comets
  • Exceptions

Formation

  • Took ~100 million years
  • We have the rules
  • Forces and interactions
    • Gravity
    • Angular momentum (Kepler's second law)
    • Particles heating up, moving faster, bumping into one another
  • Can learn about formation by looking at patterns
    • All the planets lie in nearly the same plane
    • All the planets revolve around the Sun in the same direction
    • The Sun spins in the same direction about its own axis
    • It seems as though the Sun and planets formed together from the solar nebula
  • Planet composition
    • Spectroscopic analysis --> which elements are present
    • Sun, Jupiter, Saturn --> similar elements
      • Hydrogen-dominated composition
    • Terrestrial planets and the Moon --> similar elements
      • Deficient in light gases and various ices that form from elements like oxygen, carbon, and nitrogen
      • Rarer heavy elements
    • Inner planets are made of elements that can survive heat
    • Outer solar system is much cooler so ice/gas can exist
    • Planets must form before materials get blown into outer space by solar wind

Steps

Steps in forming the Solar System

  • Start with a blob or cloud of gas and dust
    • Must have rotation
  • Begins to contract because of its own gravity
    • Or could have been hit by a shockwave
  • Proto-sun forms
  • Disk flattens and rotates faster
    • Accretion disk
      • Rotation slows collapse in the plane of rotation forming a disk
      • Smaller particles run into larger particles forming larger and large chunks
        • Planetesimals
      • Disk also heats up through gravitational contraction
        • Up to hundreds of Kelvin
      • Material near the centre is moving faster so temperature --> higher
  • Sun turns 'on'
    • Starts shining
    • Removes gases from inner areas --> leaving dust and debris
  • Gas planets can form farther Outer

Space Astronomy