Galaxies

A galaxy is a huge mass of stars, nebulae, and interstellar material. The smallest galaxies contain

about 100,000 stars, while the largest contain up 3,000 billion stars. There are three main types of 

galaxy, classified according to their shape.

·          1. Elliptical  galaxy

Which are oval shaped.

·         2.  Spiral galaxy

Which have arms spiralling.

·         3. Irregular  galaxy

Which have no obvious shape.

Sometimes, the shape of a galaxy is distorted by a collision with another galaxy.

Quasars are thought to be galactic nuclei but are so far away that their exact  nature is still uncertain.

They are compact. Highly luminous objects in the outer reaches of the known universe.

While the furthest known “ordinary” galaxies are about 12 billion light years away, the furthest

 Known quasar is about 13 billion light

year away. Active galaxies, such as seyfert  galaxies and radio galaxies, emit intense

Radiation.