WHAT IS THE SOLAR SYSTEM?

THE SUN

The sun was born about 4500 millions years ago out of a large dark cloud of gas and solid grains of dust condensed into a cluster of stars. The sun was one of these stars indeed. It had a disc of some material with nine non-light-emitting bodies in it. The disc was revolving round the sun. Later on, the nine solid bodies took off the disc and shot away. But the sun's gravity (pull) did not let them be all-free. So, they began to revolve round the sun separately along fixed paths (orbits). As for the distance, each of the nine bodies was at a different distance from the sun.

THE PLANETS

Also, the nine lightless bodies began to spin round and round in space. These bodies have been named planets (wanderers) by astronomers. Clearly, each planet had half of its surface facing the sun. So, this half was lit with sunlight while the other half was in starlit darkness. The nine planets have been named as Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.

THE SUN' S FAMILY

Six of the planets - Mercury, Venus, Mars, Jupiter, Saturn and Uranus are bright enough to be seen with the naked eye from the Earth while the remaining three are visible through a telescope only. Also, there are millions of smaller bodies in the space through which the planets revolve (move). They are moons, asteroids, comets, meteors and meteorites. All these bigger and smaller bodies make the sun's family (solar family).

THE SOLAR SYSTEM

The entire solar family and the sun itself are together known as the Solar System.

Whereas the sun is a medium-sized shining star, the planets are non-shining opaque bodies. Their surfaces are lit with sunlight - half at a time.

Remember that

1. A star is a heavenly body hot enough at its surface to shine brightly and emit light-rays in space.

2. A planet is a solid opaque heavenly body only half lit by sunlight at a time.