The Solar System and Orbits

The sun is the centre of our solar system. It’s orbited by eight planets, along with a bunch of other objects.

Our Solar System has One Star-The Sun

The solar system is all the stuff that orbits our Sun. This includes things like:

  • Planets-these are large objects that orbit a star.
  • There are eight planets in our solar system.
  • They must be large enough to have ‘cleared their neighbourhoods’.
    • This means that their gravity is strong enough to have pulled in any nearby objects apart from their natural satellites.
  • The planets are:
  • Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Earth
  • Dwarf planets, like Pluto. These are planet-like objects that orbit stars, but do not meet all the rules for being a planet.
  • Moons-these orbit planets. They are a type of natural satellite
  • Artificial satellites are satellites that humans have built. They generally orbit the Earth.
  • Our solar system is a tiny part of the Milky Way galaxy. This is a massive collection of billions of stars that are held together by gravity.

Gravity provides the force that create orbits

  • The planets move around the Sun in almost circular orbits (the same goes for the moon orbiting the earth)

  • If an object is travelling in a circle, it is constantly changing direction, which means it is constantly accelerating.

  • This also means it is constantly changing velocity (but NOT changing speed).

  • For an object to accelerate, there must be a force acting on it. This force is directed towards the centre of the circle

  • This force would cause the object to just fall towards whatever it was orbiting, but as the object is already moving, it just causes it to change its direction.

  • The object keeps accelerating towards what it’s orbiting but the instantaneous velocity (which is at a right angle to the acceleration) keeps it travelling in a circle.

    The force that makes this happens is provided but the gravitational force between the planet and the sun (or the planet and its satellites0

The size of the orbit depends on the object’s space

  • The stronger the force, the faster the orbiting object needs to travel to remain in orbit (to not crash into the object it’s orbiting).
  • The closer you get tio a star or planet, the stronger the gravitational force is
  • For an object in a stable orbit, if the speed of the object changes, the size(radius) of its orbit must do so too. Faster moving objects will move in a stable orbit with a smaller radius that slower moving ones \n \n