A galaxy is a collection of billions of stars, gas, dark matter, and dust. All of these are held by gravity. How many galaxies are there? Well, according to astronomers, there are about 100 to 200 billion galaxies in the universe. However, getting an accurate number would be impossible.
Each galaxy is named after its shape to make it easier to identify them when we look at it. Some of the common galaxies are Andromeda galaxy, Black Eye Galaxy, Milky Way, and so many more. You may be familiar with the types of galaxies. These are spiral, barred spiral, elliptical, and irregular. Let’s discuss each type below.
These galaxies are the most common ones present in the universe. Milky Way is a spiral galaxy, the same with Andromeda. A spiral galaxy is a twisted collection of stars and can be easily identified through its three components. It has a halo, disk, and bulge. The center of this galaxy is called the galactic bulge, which is like a nucleus that contains a sphere-shaped bulge that comprises the stars but without gas and dust. The one that is orbiting the bulge is the disks of stars that circle the galaxy. These are the arms that contain lots of gas and dust, as well as young stars that shine brightly. Spiral galaxies are surrounded by dark matter. As per scientists, over 70% of all galaxies are spiral.
Barred Spiral Galaxy
These galaxies have almost the same features as the regular spiral galaxies. But it has a bar through the center. The bar that contains the bright stars which lie on the center of the bulge extends to its disk. The bulge consists mostly of older and red stars. It also has a little action going on in there. But the bar and arms of barred spiral galaxies have many activities which include the formation of the stars. Unlike the spiral galaxy, the barred spiral is mostly star (less gas and dust).
These are galaxies that are spherical in shape without a bulge in the center. This galaxy is still brighter in the center, even without the nucleus. The outer edges are less bright. Elliptical galaxies can be round or long or shaped like a cigar. Spreads throughout the galaxy are stars, gases, and other elements. These galaxies have three dimensions, but when we look at the sky, we can only two of them. Elliptical galaxies exist because of the collision of many smaller galaxies and said to be the largest single star systems in the whole universe.
These galaxies have no regular structure, or they are irregular when it comes to shaping. One example of an irregular galaxy that we can see from earth is Small Magellanic Cloud. These galaxies may show that they have bars structure, active formation of stars, a trace of a spiral galaxy, etc. These galaxies are also continually moving away from the center of the universe. Since there is only a very few stars formation on these galaxies, they are often considered as the endpoint in the evolution of galaxies.
Although there are billions of galaxies in the universe, only a few have been given established names. Astronomers have been working hard to get a better picture of the structure of the universe. It is hard to understand the size of the universe given than there are billions of galaxies, and our galaxy alone is composed of over a billion stars. Studying about galaxies is difficult, but thanks to our astronomers, we were able to learn something about their evolution, something about our universe, but most importantly, facts about the formation of our stars.