the solar system

• the solar system (definition):

  the solar system consists of a star (the sun) and all the objects orbiting it, these include the planets, moons, dwarf planets, asteroids and comets.
• the sun is at the centre of the solar system.
• planets orbit the sun, moons orbit planets.
• the asteroid belt is a region between the orbits of mars and jupiter where there are thousands of rocky asteroids and dwarf planets.
• a dwarf planet is a body similar to a planet but too small to be called a planet. pluto is an example of a dwarf planet.
• comets are formed from ice and dust beyond the orbit of neptune and have highly elliptical orbits.
• the sun is not the only star with planets, other stars have planets in their planetary systems.
• the solar system diagram:

  
• distances in space:

  as distances in space are so large it is impractical to use metres or km, therefore different units are used:

  • astronomical unit= the mean distance from the sun to the earth (approximately 150000000km)
  • light year= the distance light travels in one year.
• planets in the solar system:

  although you will not need to remember the specific numbers below, you will need to remember the order and recognise patterns in the data. for example, as the distance from the sun increases so does the time for one orbit. at the distance from the sun increases the temperature decreases; except for venus which has a thick atmosphere which keeps more heat in.

  
• formation of the solar system:

  • the solar system formed from a cloud of gas, mainly hydrogen and helium, and dust ejected from a supernova. gravitational forces caused this cloud to collapse and the particles to collect together.
  • as the cloud collapsed it began to spin, this made it turn into a disk.
  • the centre of the disk became the sun and the rest collected together to form the planets.
  • the inner planets are rocky because it was too close to the sun for the light gaseous elements to condense and so the elements were pushed further away from the sun.
  • the outer planets are gaseous because it is further from the sun and the gaseous elements were able to condense and collect to form the gas giants.