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World Geography / Universe and Solar System

Origin and Evolution of Solar System

There are many theories that are being proposed for the origin and evolution of solar system. The Universe comprises of large number of heavenly bodies. The basic unit of the Universe is the star. All stars are grouped into Constellations and group of Constellations is called Galaxy. Universe is made up of 1 million galaxies. In every Galaxy, there are more than 1 billion stars.

Where are We in the Milky Way

Our galaxy is Milky Way. It has more than 1 billion stars. One such star is Sun. Sun has its own family named Solar System. It has planets, dwarf planets, meteoroids, comets, dust and asteroids.

99.8% of mass of solar system is with Sun. 0.1% of mass of solar system is in Jupiter. Remaining 0.1% of mass is stored with all other bodies, where Earth is located.

On earth, 71% is water and 29% is continent or land. 4-40 million species are living either on the land or the water on the earth. Homo sapiens is one such species.

Formation of the Solar System Theories

  • There are large number of theories available regarding the origin of Solar system. It is said that 4.5-5 billion years back, earth and the solar system came into existence. Some contemporary studies also say that it got originated around 9-11 billion years back.

  • All the theories can be classified into two categories of theories, (i) Catastrophic Theories, according to which the origin of the Earth is a Celestial or Cosmic accident (not accepted now) and (ii) Evolutionary Theories, according to which the Earth got evolved through process of evolution (accepted nowadays).

    Catastrophic Theories

    • Jeans and Jeffreys Tidal Hypothesis (Hit and Run Hypothesis) - According to this theory, Sun was approached by another star, because of which huge amount of mass came out from Sun due to gravitational pull and formed planets.

    • Supernova Hypothesis of Hoyle - Hoyle in his supernova concept postulates that there existed the primitive Sun and a companion star of giant size.

      The companion star experienced nuclear explosion to become a Nova. When the explosion is intensely high, the bursting star is called Supernova. The explosion led to emission of large amounts of gaseous matter.

      The intense heat and atomic reactions are responsible for the formation of heavier elements like helium, oxygen, carbon, nitrogen, etc. The heavier elements thus formed, are the source material for the formation of the earth.

    • Russell and Lyttleton's Binary Star Hypothesis - The Binary hypothesis believes that many stars exist as pairs in the universe. Our solar system was also having the Sun and other smaller star.

      Another bigger star approached the companion star and matter came out of companion star which became the source for our earth contents.

    • Interstellar Hypothesis - Otto Schmidt proposed that interstellar dust around the Sun got turned into planets.

    Evolution Theories

    • Kant and Laplace's Nebular Hypothesis - According to this theory, the original mass of the Solar system was in the form of Nebula (hot rotating gaseous mass in the form of series of rings).

      Gradually the rings got separated, the gaseous matter cooled down and coalesced and turned into planets and central portion was turned into the Sun. This is the most accepted theory. Other theories also support the Nebular theory.

    • Big Bang Theory - According to this theory, all the matter of the Universe was at one place (super celestial body).

      There was an explosion and the matter got disintegrated and the matter came out to form to planets and stars. According to Rig Veda, Adi Purusha is the super celestial body.