The Solar System

The Solar System :

Ø The Solar system consists of the sun, the eight planets and their satellites (or moons), and thousands of other smaller heavenly bodies such as asteroids, comets and meteors.

Ø The sun is at the center of the solar system and all these bodies are revolving around it.

Ø The gravitational pull of the sun keeps all the planets and other objects revolving round it. Thus, the motion of all the members of the sun.

Ø Planets revolve around the sun in elliptical orbit.

Ø In the solar system the planet nearest to the sun is Mercury and the planet farthest from the sun Neptune (not Pluto).

Ø The size of solar system has been estimated to at about 10^5 A.U.

Ø The solar system is dominated by the sun which accounts for almost 99.9% of the matter in the whole solar system.

Ø The sun is also the sound of all the energy in the solar system.

Ø Mercury, Venus, Earth, Mars are called terrestrial planets and Jupiter, Saturn, Uranus and Neptune are called gaseous planets.

Star

Star :

Ø Clumps of dust and gas in a nebula come together due to gravity and form stars.

Ø Stars are made of hot burning gases.

Ø They emit light of their own and are very large and very hot.

Ø Light takes about 4.3 years to reach us from the next nearest star Proxima Centauri.

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The Big Bang Theory

The Big Bang Theory :

Ø All the matter in the universe was originally a concentrated lump called primeval atom.

Ø Big bang was an explosion that occurred 15 billion years ago, leading to the formation of galaxies of stars and other heavenly bodies.

Ø Since then, all the galaxies have been flying away from one another causing expansion of the universe.

Galaxy

Galaxy :

Ø A Galaxy is a vast system of billions of stars, which also contains a large number of gas clouds (mainly of hydrogen gas) and dust, isolated in space from similar systems.

Ø There are about 100 billion galaxies (10^11 galaxies) in the universe, and each galaxy has, on an average, 100billion stars (10^11 stars). So, the total number of stars in the universe is 10^22 stars.

Ø The Milky Way galaxy is the home of the Earth and our solar system. It is spiral in shape.

Ø Milky Way galaxy was formed 5 billion years after the Big Bang.

Ø Latest known galaxy is the Dwarf Galaxy.

Ø According to the modern thought, universe can be classified into two parts namely :

1.     Atmosphere, and

2.     Space.

Ø Origin of the universe is explained by the Big Bang Theory, formulated and proposed by the Belgian astronomer and cosmologist Georges Lemaitre.

Ø Andromeda is our nearest galaxy.