Theory 
Solar System Figures| CONTENT - Most useful, basic data about the nine planets of the solar system! |
 | A artist's view of figures about a planet. picture site 'Amateur Astronomy' |
Five planets were known since the oldest Antiquity: Mercury, Venus, Mars, Jupiter, and Saturn, as they might be spotted naked-eye. It was not until 1781 that a new family member was added, when Uranus was discovered by Sir William Herschel due to the use of astronomical instruments. Neptune in 1846, then Pluto in 1930 were, as far as they are concerned, discovered through the use of astronomical computations. Their discoverers were Galle and Clyde W. Tombaugh respectively. The first four planets from the Sun (Mercury, Venus, Earth, Mars) along with Pluto are termed "terrestrial planets", due to their rocky composition as Jupiter, Saturn, Uranus and Neptune are termed "gas giants" as they are are mostly made of gas
check a table of figures related to the solar system planets
