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 to 3,000 billion stars . There are three main types of Galaxy , classified according to their shape ;elliptical ,which are oval shaped; spiral, which have arms spiraling outwards from a central bulge; and irregular, which have no obvious shape .Some times , the shape of a galaxy is distorted by by a collision with...