UNIVERSE

- The study of universe is known as Cosmology.

Cosmology =Cosmos (Universe)

                                  +Logos (Study)

- The universe is commonly defined as the totality of everything that exists including all physical matters and energy, the planets, stars, galaxies and the contents of intergalactic space.

- The universe comprises of billions of galaxies. The galaxies are made up of millions of stars held together by the force of gravity and these stars account for most of the masses of the galaxy. Andromeda is our nearest galaxy.

- Our own galaxy is called the Milky Way (or the Akash Ganga) and it contains about 100 billion stars and one of these is our Sun.

- Planets and other objects go round the Sun and make up the solar system with the sun at the centre. Latest known galaxy is the Dwarf Galaxy.

- Evolution of universe is explained by the Big Bang theory. Big Bang was an explosion that occurred 15 billion years ago, leading to the formation of galaxies of stars and other heavenly bodies.

               SOLAR SYSTEM

The solar system comprises of the Sun and it's eight planets, which are believed to have been developed from the condensation of gases and other lesser bodies.

Components of the Solar System

The Sun is at the centre of the solar system and all the planets revolve around it in elliptical orbit. It is the nearest star to the Earth. The size of solar system has been estimated to about 10⁵ AU.

Origin of Earth

          Other components of solar system are

- The Sun, eight planets (excluding Pluto) and their respective satellites.

- Five Dwarf planets (Ceres, Pluto, Eris, Makemake and Haumea).

- Interstellar debris such as asteroids, meteoroids, comets.

- The electrically charged gases, called plasma.

- Interplanetary dust particles are cosmic dust which pervade between planets in the solar system.

- The Sun, eight planets ( excluding Pluto), their satellites and 5 dwarf Planets are the main components of the solar system. It also consists of asteroid, meteoroids, comets, electrically charged gases called plasma, Interplanetary dust particles. Components other than these are known as Small Solar System Bodies (SSSB).