Galaxy is made up of a gigantic collection of dust, gas and constellations of stars. A Constellation is a group of stars. For example Big Dipper.

All the matter in the galaxy are held together by gravity. As for Milky Way, our galaxy, there is a immense black hole in the center.

Just a small patch of space in the universe would have 10,000 galaxies. It were estimated by scientists that the universe could have a 100 billion galaxies or more.

Milky Way is shaped like a spiral. Some galaxies are fashioned like our galaxy. And others are smooth and oval shaped. These are named as elliptical galaxies. There galaxies that have irregular shapes like blobs which are called irregular galaxies

All kinds of electromagnetic radiations (from radio waves to x-rays) are emitted from galaxies. The astronomers will get a clear picture of how the galaxis looked like from this 'lights waves' after processing them.

To determine the distances of galaxies we can observe the brightness of the stars. With such stars we can measure up to 300 million light years away. (Credit:space-facts.com/galaxies & en.wikipedia.org/wiki/Galaxy)