Erin Wilson, of Fielding Intermediate School, asks :-

Who first discovered the planets and how did they get their names?

Frank Andrews, an astronomer at the Carter Observatory, Wellington, responded.

The bright planets of our Solar System: Mercury, Venus, Mars, Jupiter and Saturn have been known since before historical records were kept. They are bright enough to be easily seen with just the naked eye. In ancient times each country had its own names for the planets. Because our western culture owes so much to the ancient Romans and their language, known as Latin, we have retained the Roman names for the planets. These names were those of ancient Roman gods.

The three outer planets were too distant from the Sun and the Earth so were not discovered until after the invention of the telescope. The tradition of using the names of ancient Roman gods was continued, hence we have Uranus, Neptune and Pluto.

The first of these to be discovered was Uranus in 1781. This was a just reward for William Herschell of England who had been making a careful and systematic survey of the sky.

Johann Galle of the Berlin Observatory discovered Neptune in 1846 and Clyde Tombaugh discovered Pluto in 1930.

For a long time a tenth planet was postulated to explain the apparent slight wandering of these three planets from their calculated paths. However recent space craft visits to Uranus and Neptune enabled their masses to be measured very accurately. When these values are used in the calculations their paths agree with predictions so the need for the existence of a 10th planet vanished.