The Solar System
The Solar System consists of (from the Middle outwards) The Sun, an average sized star of average brightness, Mercury, Venus, the Earth and Mars, four small rocky dense planets and then, seperated by the Asteroid belt, Jupiter Saturn Neptune and Uranus, four giant and not very dense ‘gas’ planets. Then there are the dwarf planets - a category of object invented in 2006 to describe other large objects orbiting the Sun which are however too small to be termed ‘planets’. Currently there are three dwarf planets - Ceres, which is situated in the asteroid belt and is the largest known asteroid in the Solar System, Pluto, which lies beyond Neptune, and Eris, the largest of the dwarfs, which lies beyond Pluto.
In figures, the Solar System is made up of: Sun: 99.86%
Planets: 0.135%
Comets: 0.01%
Satellites: 0.00005%
Asteroids: 0.0000002%
Meteoroids: 0.0000001%
Interplanetary Medium: 0.0000001%
The Sun is the centre of the Solar System and the Earth orbits it at an average distance of 1 AU (150 millon kilometres). This is quite far and it takes the Sun’s light 8.3 minutes to reach us. The are 8 planets which orbit the Sun, the smallest being Pluto and the largest being Jupiter. The Solar System isn’t just made up of planets though and in between the orbit of Mars and Jupiter there is what’s known as the asteroid belt. This belt consists of many, many asteroids which also orbit the Sun. You can find out more by visiting the asteroids or Meteors pages.
The Kuiper belt is a belt of icy, frozen, lifeless lumps of ice which sometimes enter the inner Solar System. I goes round the moon in a highly elliptical fashion, at its closest being just beyond Neptune yet at its furthest linking up with the Oort cloud, about 500,000 AU or 2 light years away!
The Solar System was born when a cloud of gas (made up of about 75% Hydrogen, 25% Helium and nearly 1% heavier elements) condensed enough to form solid objects, which slowly joined to make the Solar System as we know it. Ever wondered why the four planets closest to the Sun are small and rocky whereas the ones further away are big and gassy? Well, it’s because close to the Sun it was too hot for most of the gas to survive so it got driven away from the sun or it vapourized leaving the inner planets with thinner atmospheres.
Monday, June 25th, 2007