HMDUK 12 How many planets are there?

How many planets are there? There are eight chief planets which revolve about the sun and comprise what is called the solar system. The names of these planets in the order of their distance from the sun are Mercury, Venus, the Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Mercury and Venus are called the inferior planets because the lie between the earth and the sun. Mars, Jupiter, Saturn, Uranus and Neptune are known as the superior planets. The inferior planets move about the sun, faster than the earth and the superior ones more slowly. All the planets belong to one family, but they differ in size and temperature. Some are smaller than the earth, some hundreds of times larger. Some are very hot, others very cold. Jupiter is the largest of all the planets and Saturn one of the most famous because of its beautiful luminous rings. In 1930 a new planet called Pluto was discovered. Some astronomers consider it to be a major planet, but this has not yet been proved and is possibly merely an unusual minor planet.