The Solar System consists of the sun, the nine planets and their satellites (or moons), and thousands of other smaller heavenly bodies are revolving around it. The sun holds them together by its great gravitational pull. In other words, the motion of all the members of the Solar System is governed mainly by the gravitational force of the sun. The sun is a star. It is the star round which the earth and other planets revolve. In a way we can say that the sun is the head of Solar family or solar system. The sun is the only star having a known systems of planets with life on one of its planets, called earth.

Planets are solid heavenly bodies which revolve round the sun is closed elliptical paths. A planet is made of rock and metal. It has no light of its own. A planet shines because it reflects the light of the sun. Since the planets are much nearer than the stars, they appear to be big and do not twinkle at night. The planets move round the sun from west to east, So the relative positions of the planets keep changing day by day. There are I major planets including the earth.

(i) Mercury, (ii) Venus, (iii) Earth, (iv) Mars, (v) Jupiter, (vi) Saturn, (vii) Uranus, (viii) Neptune, (ix) Pluto

Out of nine planets of the Solar System, Mercury, Venus, Mars, Jupiter and Saturn can be seen easily with the naked eye. Three planets, Uranus, Neptune, Pluto are very far off and have been discovered with the help of telescope. The ninth is our own earth. Mercury is the smallest planet in the solar system and it is nearest to the sun. Since the planet Mercury is closes to the sun, It is very hot during the day and life is not possible on it. Mercury is a fairly bright planet which can be seen in the east just before sunrise or in the west just after sunset the planet 'Venus' is the brightest object in the night sky.