Galaxies

                        

                            Galaxies

A Galaxy is a huge mass of stars and other heavenly bodies assembled in the Universe by gravitational force. The size of the Galaxies differ according to the number of stars The smallest ones are of about 1,00.000 stars while the largest Galaxies contain about 3,000 billion stars.

 

Galaxies are classified into three main groups according to their shape.

• Elliptical Galaxy (ovel shaped)

• Spiral Galaxy (with spiralling arms from a center bulge)

• Irregular Galaxy (without an apparent shape)

The Milky Way Galaxy is included in the group of spiral Galaxies. Sometimes the shape of the Galaxy is distorted due to the collision of two Galaxies. The changes occuring in their nuclei form supermassive objects like black holes. Such changes occurred billions of years ago. Now they appear as compact, highly luminous objects called Quasars. These Quasars are very far away so that their exact nature is still unknown. Some Galaxies are isolated while others are active Galaxies and they emit extra large amount of radio energy. These radiations are thought to be caused by the presence of black holes.