What is the Milky Way?
This galaxy among the billions of stars in the universe is given the name “Milky Way” because of the way it appears to those viewing it from the Earth. Most of the stars in our galaxy appear so close together that there is a “milky” white band in the night sky. All of the stars we see in the night sky are part of this galaxy. It’s just that the closer stars appear to be separated while the majority of stars appear close together, forming the Milky Way.
Human beings viewing the Milky Way from Earth don’t see anything close to the true brightness of the stars or the Milky Way. Light pollution from man-made sources and other matter in “space” serves to block some of that brightness. There is a center to the galaxy, located in about the same area as the star Sagittarius. A huge amount of stars makes up the galaxies, including the Milky Way. The force of gravity keeps our galaxy, and others, in a spiral shape.
Our sun is one of the stars in the Milky Way. It warms us and sustains life because it is a living, healthy star that is just the right distance from the Earth. It may seem that it is the largest and most important star in the galaxy. To us, it is. But our solar system is just one tiny part of one of the spiral arms in the galaxy. There appear to be six distinct arms to this spiral galaxy. Stars that make up the Milky Way stretch for thousands of light years across the universe.
The name of the galaxy is descriptive and comes from the Latin language. Men first began to take note of the connected “band” of milky white light in the 18th century. According to recorded history this was the first time the galaxy was made up of millions upon millions of stars.
How many stars does it take to form our Milky Way? Scientists can only estimate the number based on what they are able to observe with powerful microscopes. An educated guess puts the number at more than 200 billion stars and maybe twice that many. There is no perfect, curved arm or line that forms the Milky Way. In fact, scientists see a bulge or larger grouping of stars in the center. This galaxy is part of a spiral arm called Orion.
It is difficult to understand that the shape of the galaxy is determined by constant rotation, just as the planets are in constant motion around the Sun. Scientists have determined that the galaxy closest to ours is the Andromeda Galaxy. This is also a spiral-shaped galaxy. These two galaxies are a small part of a large group of distinct galaxies. Remember this when you are standing on the Earth at night and see a band of “milky” light that seems almost solid but is actually millions of stars seen from our unique perspective.