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.