Solar System is the name given to a collection of heavenly bodies encircling around the sun. The sequence of planets is in their ascending distance from the sun.

  1. Mercury
  2. Venus
  3. Earth
  4. Mars
  5. Jupiter
  6. Saturn
  7. Uranus
  8. Neptune
  9. Pluto

However, Pluto is now not considered as a planet in our solar system. Sun covers around 99.8% of total mass of the solar systems. Solar system is considered to have the shape of flat disc because all the planets revolve around the sun and the orbit of planets is elliptical and in same plane. All the planet revolves around the sun is same direction making orbit elliptical. The planets rotate on their axis in the same direction of revolution around the sun only Venus and Uranus more in counter clockwise direction. If one ignores a few exceptions, satellite system follows the same movement by the longer planets they orbit. Every planet has different composition and different densities. Some of the densities are as follows: –

Planet Density
Mercury 3.8
Venus 4.8
Earth 5.5
Mars 3.3


The above mention planets have huge quantities of oxygen, silicon and iron. Other planets which are huge in size have low densities. These include Jupiter, Saturn, Uranus and Neptune. The cause is that they are composed of hydrogen, helium and ammonia and methane. The term asteroid is basically used to refer a whole series of very small planets or fragments of planets. These small pieces revolve around the sun and are mostly focus between the orbits of mars and Jupiter. The sequence of planets according to the size of descending order is as follows: –

  1. Jupiter
  2. Saturn
  3. Uranus
  4. Neptune
  5. Earth
  6. Venus
  7. Mars
  8. Mercury
  9. Pluto (if it is included in planets).

The sun is 109 times bigger than the earth. Its weight is around 2 x 1027 tons. The surface temperature is 6000oC. The average distance of the sun from the earth is approx 150,000,000 kms. The light emitted by the sun reaches the earth in about 8 minutes.

Another celestial event is known as meteors which are formed by the mixture of dust and gas. The meteors burn in atmosphere due to friction and gravity present in the space. Some of the meteors completely burn whereas some of them partially burn and reach the earth in the form of rockets. Such are known as meteorites comets are remmats that form the solar system. They (comets) line in the cold outer range of the solar system in the outermost part of the universe. In terms of properties comets are non-luminous objects which have on tails. The comets further move enormously in the orbits around the sun. Some of the comets come out due to gravitational force of stars whereas some comets out of their orbit. Some comets are lost in the solar system which gets composed of brilliant long tailed comets. These are visible from earth. The comets consist of three parts: –

  1. A Nuclear
  2. A Head
  3. A Tail

A comet may have one out of three kinds of orbit which include the following: –

  1. Elliptical – If the comet approaches the sun and he does not possess the speed of overcoming the sun’s gravity.
  2. Parabolic – Here, the comet has just enough speed to counter-balance the gravity of the sun.
  3. Hyperbolic – If the comet has the speedy to overcome sun’s attraction.

Some comets reproach sun’s gravity in a particular time period. Such comets are known as periodic comets. However, the parabolic comets are divided into two categories namely: –

  1. The short period group
  2. The long period group

The short period group has a period less than 2000 years; for example, Halley’s Comet, which reappears on earth every 76.3 years. The comets those have periods of thousands of years are known as long period group comets.  The great comet of 1811 comes back every 3000 years.