What are the three types of galaxies? Most people have a general idea of what a galaxy is, but when asked to describe the difference between the three types, they have no idea where to start. To begin, it is important to understand what a galaxy is in the first place. Galaxies are concentrations of stars, gas, dust, and dark matter. They come in a variety of shapes and sizes and some are fated to collide, like the Milky Way and Andromeda. 

 

There are three main classifications of galaxies: elliptical, spiral, and irregular. Elliptical galaxies account for about one third of all of the galaxies in the universe. They vary from elongated shapes and sizes to smaller and more circular shapes and sizes. Compared to the other two types of galaxies, they contain a lesser amount of gas and dust, but are replaced by older and dormant stars. In rare cases these galaxies can merge together to form giant galaxies, spanning roughly 300,000 light years, called giant ellipticals. 

Spiral galaxies are typically more flat and contain more blue stars. They often have yellowish bulges in their centers caused by large amounts of gas and dust that are pulled into the center by a strong gravitational force. An example of a spiral galaxy is the Milky Way Galaxy that we reside in. If you ever go outside and look up at the Milky Way, you will see that the majority of the galaxy is only in one strip along the sky. That is due to the aforementioned flat characteristics of a spiral galaxy. There appears to be a strip of concentration because we are looking out along the galaxy’s plane. 

Spiral galaxies are broken into two different types: normal spirals and barred spirals. Barred spirals are exactly as the word describes them. There is a bar of stars that runs through the center bulge. In a normal spiral there is no bar of stars running through the center, but eventually there will be. This is due to the theory that spiral galaxies are actually stars being formed. Spiral galaxies are constantly collecting dust, gas, and debris. Eventually, these collected masses will combust and become a star!

 

Finally, there are irregular galaxies. Irregular galaxies are not typical galaxies. They are formed with very little dust and are neither disk-like or elliptical. They are typically incredibly old as they existed before being sucked into a spiral or elliptical galaxy.

 

Beyond just the different types of galaxies, it is also easy to wonder how these different types of galaxies came into existence. The typical astronomer will tell you that it all began during the big bang, the explosion which many believe created the universe 10 to 20 billion years ago. They believe that the gravity waves caused by the big bang began to compress and decompress the gasses that were floating in the universe. Then, according to the bottom-up theory, clusters began to form and assembled into larger units that today we know to be galaxies.