The solar system

• There are 8 major planets with nearly circular orbits.
• Pluto and Eris are smaller than the major planets and have more elliptical orbits.
• Sun:

  • Over 99.9% of solar system's mass, made mostly of Hydrogen/Helium gas (plasma)Converts 4 million tons of mass into energy each second.
• Mercury:

  • Made of metal and rock. (Large iron core)
  • Desolate, cratered.
  • Very hot during the day - 425 C, and very cold during the night - -170 C
• Venus:

  • Size is identical to Earth.
  • The surface is hidden by clouds.
  • Hellish conditions due to an extreme greenhouse effect.
  • Hotter than Mercury: 470 C (day and night)
• Earth:

  The only surface liquid water in the solar system.
• Mars:

  • Looks like Earth
  • Giant volcanoes, a huge canyon, polar caps.
• Jupiter:

  • Much further away from the sun.
  • The surface is made up of mostly Helium and Hydrogen.
  • There is no solid surface.
  • 300 times more massive compared to Earth.
  • Many moon rings.
  • It has 4 Galilean moons
• a Saturn:

  • Giant and gaseous like Jupiter.
  • Have rings.
  • Many moons, including cloudy Titan
  • Rings are not solid; they are small chunks of ice and rock each orbiting like tiny moons
• Uranus:

  • Larger than Earth but smaller than Jupiter and Saturn.
  • surface is made of helium / hydrogen gas and hydrogen compounds.
  • Extreme axis tilt
  • Have moon and rings.
• Neptune:

  • same size as Uranus.
  • surface is made up of hydrogen / helium gas and hydrogen compounds.
  • Less axis tilt.
  • Have many moons (including Triton)
• Pluto and other Dwarf planets:

  • smaller than major planets
  • Icy, comet -like composition.
  • Pluto's main moon is Charon.
• All large bodies in the solar system orbit in the same direction and in nearly the same plane.
• 2 major types of planets:

  Terrestrial planets and Jovian Planets
• Terrestrial planets are rocky, small and close to the sun.
• Jovian planets are gaseous, larger and further away from the sun.
• Many rocky asteroids and icy comets populate the solar system.
• Conservation of Energy and Angular momentum:

  • The system heats up as it collapses due to the conservation of energy.
  • Rotation speed of the cloud from which our solar system formed must have increased as the cloud contracted.
• Flattening: Collisions between particles in the clouds caused it to flatten into a disk that rotates in an orderly fashion.
• Where did the Solar System come from?

  • Galactic recycling built the elements from which planets formed.
• What caused the orderly patterns of motion in our solar system?

  • solar nebula spun faster as it contracted because of conservation of angular momentum.
  • Collisions between gas particles then caused the nebula to flatten into a disk.
  • We have observed such disk around newly formed stars.
• Inner parts of disk are hotter than outer parts.
• 1. Inside the frost line: too hot for hydrogen compounds to form ice.
  2. outside the frost line: cold enough for ice to form.
• How did terrestrial planets form?

  • Grains stick to one another via electromagnetic force to form planetesimals (small bodies orbiting the sun)
  • Gravity draws planetesimals together to form planets.
  • This process of assembly is called accretion.
• Accretion of planetesimals: Many smaller objects collected into a few larger ones forming a planet.
• How did Jovian planets form?

  Accretion of gas and dust in the protoplanetary disk.
• Asteroids and Comets are leftovers from the accretion process.