A GALAXY IS A HUGE MASS OF STARS. Nebulae and , and interstellar material. The Smallest galaxies contain about 100,000 stars while the largest contains about 3,000 billion stars. There are three main types of Galaxy. Classified according to their Shape :
Elliptical Galaxy which are Oval shaped:
Spiral Galaxy Which have arms spiralling outwards from the central bulge
Irregular Galaxy which has no obvious shape.
Quasar (Quasi - stellar objects)
Sometime, 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 highly uncertain. They are compact, Highly luminous objects in the outer reaches of the known universe: while the furthest known "ordinary" galaxies are about 10 billion light years away. The furthest known quasar is about 15 billion light years away.
Seyfer Galaxy
Radio Galaxy
Active Galaxies such as Seyfert galaxies and Radio Galaxies, emit intense radiation. In a Seyfert galaxy, This radiation comes from huge lobes on either side of the galaxy. The Radiation from Active galaxies and quasars is thought to be caused by black holes
black hole
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