(a) Describe the solar system. (b) Outline four characteristics each of the following planets: (i) Pluto; (ii) Mercury

Answer Details

(a) The Solar System

The solar system consists of the Sun and all the heavenly bodies held by its gravitational pull and revolving round it. The Sun is at the centre of the system and is the main source of light and heat.

It consists of eight major planets—Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune—which move round the Sun in elliptical orbits. The planets do not produce their own light; they shine by reflecting light from the Sun.

The solar system also contains natural satellites (moons), asteroids, comets, meteoroids and dwarf planets. Pluto, formerly regarded as the ninth planet, is now classified as a dwarf planet. Mercury is the closest planet to the Sun, while Venus is the hottest planet. Jupiter is the largest planet.

(b) Characteristics of Planets

(i) Pluto

• It is a dwarf planet located in the outer region of the solar system.
• It is very far from the Sun and is therefore extremely cold.
• It takes about 248 Earth years to complete one revolution round the Sun.
• It has a highly elliptical and inclined orbit, and it has moons, the largest of which is Charon.

(ii) Mercury

• It is the closest planet to the Sun, at about 58 million kilometres away.
• It is the smallest of the eight major planets.
• It takes about 88 days to complete one revolution round the Sun.
• It has no natural satellite and has very high daytime and very low night-time temperatures. Venus, not Mercury, is the hottest planet.