The Solar System

Until recently it was thought that there were nine planets in the Solar System, called Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. However, the outermost planet, Pluto, has been reclassified as a Dwarf Planet. To remember the planets of the Solar System in order I often use the following mnemonic: My Very Elderly Mother Just Shot Uncle Ned's Pigeons (although, now ... My Very Elderly Mother Just Shot Uncle Ned ... as Pluto is no longer a planet). The first letters of the mnemonic are the same as the first letters of the planets of the Solar System from the Sun outwards.

The Sun

This is the star in the Solar System. It is classified as a yellow dwarf. It gives out huge amounts of electromagnetic radiation.
The Sun is much bigger than all of the other objects in the solar system. In fact its diameter is the equivalent of 109 Earths placed side-to-side. The Sun's mass is the equivalent to nearly 333,000 Earths put together. It is so heavy that the density inside the star causes nuclear fusion to occur - which is what releases all the electromagnetic energy.

The Planets

The following table includes some data about the eight planets in our solar system. The orbital period is a measure of the length of one year (in Earth days) on that planet. The average speed is a measure of how fast that planet is travelling through space. And the radius is a measure of the size of each planet.

Most planets in the solar system have their own satellites or moons. Sometimes the moons of a planet are very large - for example, Ganymede (a moon of Jupiter) has a bigger radius than the planet Mercury. At the other end of the scale Jupiter has another moon, Euporie, which is only 2km in diameter.