What is the Solar System?

          The Solar System consists of the Sun, the nine planets and their moons, asteroids comets, meteoroids and other debris. The Sun holds all these objects in fixed orbits by its strong gravitational pull. The Sun makes up 99% of the solar systems mass. Most of the solar system is a vast emply space.

          The study of the nine planets is necessary for the study of the Solar System.

Mercury: Mercury is the smallest planet of the Solar System and nearest to the Sun. It takes 88 days to complete one revolution round the Sun and the same time to complete one rotation on its own axis. It is difficult to see it very clearly because of its extreme proximity to the Sun. However, studies reveal that there are many hills on its surface. There is no water on this planet. Its distance from the Sun is 58 million kms or 36 million miles.

Venus: Venus is the planet nearest to the Earth. Its distance from the Sun is 108 million km. It is approximately of the same size and weight as is the earth. It takes 224.7 days to complete one revolution round the Sun and thirty days to complete one rotation on its own axis. It has some atmosphere. Man has already launched his spacecraft on this planet.

Earth: Earth is the only planet of the Solar System that is inhabited by living beings. Its distance from the Sun is 150 million km. It takes 365  days to complete one revolution round the Sun. To complete one rotation on its own axis, it takes about 24 hours. The Moon is a satellite of the Earth and revolves round it.

Mars: Mars is red in appearance. Besides the Earth, this is the only planet where signs of vegetation are found. Studies have revealed that it has mounts of ice on its poles. Its distance from the Sun is 228 million km. It takes about 687 days to make one revolution round the Sun. On its own axis, it makes one rotation in 24 hours and 37 minutes. It has two small moons—Phogos and Diamos.

Jupiter: Jupiter is the biggest planet of the solar family. Its distance from the Sun is 778 million km. or 484 million miles. It completes one revolution round the Sun in 11.8 years, whereas it makes one rotation on its own axis in 9 hours and 50 minutes. It is 317 times heavier than the Earth. Being at a great distance from the Sun, it is an extremely cold planet. It has altogether 14 moons.

Saturn: Saturn is a peculiar planet of the Solar System. Its distance from the Sun is 1,427 million km. It takes 29  years to complete one revolution round the Sun, but only 10 hours and 14 minutes to make one rotation on its own axis. There are many rings round it. It has 10 moons.

Uranus: Uranus completes one revolution round the Sun in 84 years. But it takes 10 hours and 49 minutes to make one rotation on its own axis. Its distance from the Sun is 2,870 km. It has five moons.

Neptune: Neptune takes 164.8 years in making one revolution round the Sun. It completes one rotation on its own axis in about 15 hours and 48 minutes. Its distance from the Sun is 4,497 million km. It has two moons.

Pluto: Pluto is the farthest planet from the Sun. It completes one revolution of the Sun in 248.4 years. On its own axis it takes 153 hours to complete one rotation. Its distance from the Sun is 5,900 million km. It has one moon.        

           In addition to these planets, there are about 1,700 asteroids which also revolve round the Sun. They lie between Mars and Jupiter. They are, in fact, small pieces broken away from the bigger planets and since have been revolving round the Sun.