Most people know that Earth resides in the Milky Way Galaxy. There has even been a recent search to see what is beyond our galaxy. There are many details that most of us have forgotten, however. Elementary age students learn a lot about the galaxy, yet the subject rarely comes up after that. It can be interesting to revisit this important part of science education and see what there is to learn, as well as the new developments.
The Milky Way has been studied from many angles. Some studies focus specific interior details, while others take a broader look. Our galaxy has a certain shape. This is interesting because we often think of space as a place where everything just floats around haphazardly. Somehow, galaxies manage to maintain a shape of sorts. The Milky Way is referred to as barred spiral. Our solar system sits out on the edge of one arm of it. Ancient scientists referred to the “milky” look of the sky as presented by the millions of stars. They also called it a river or path. The size of the Milky Way is measured in light years, and is about 100,000 light years from end to the other.
The barred spiral shape consists of specific structure that gives it this shape. Pictures taken from about the Milky Way show its structure the best. The center has a bulge and is considered extremely dense, unable to be seen through from one side to the other. Four spiral arms are wrapped around this center bulge. Our universe contains several other galaxies of the same structure. About two-thirds of the known galaxies are barred spirals. The word “barred” refers to a bar that spans across the center of the galaxy. This bar also has two arms that extend from it, with two small spurs that also extend from these.
Earth, and its solar system, are in a very specific place. One of the mentioned spurs contains our solar system. This is called the Orion Arm. There are two more significant arms, Perseus and Sagittarius, that the Orion Arm sits between. The earth, along with our entire solar system moves with these arms as the Milky Way rotates. This rotation is constant, carrying the solar system through space at about 515,000 mph. This is incredibly fast, and yet it would still take about 230 million years to travel around the entire Milky Way.
Stars make up the majority of the content in the arms of the galaxy. There is also a substantial amount of gas and dust. The quantity of stars inside the arms is more condensed, resulting in a type of traffic back-up. Due to this congestion, the stars move slowly inside the arms. When things attempt to move through these dense areas, compression occurs. This compression results in the formation of more stars. The arms are inside a part of the galaxy called the disk. This part is only about 1,000 light years in size.
The Milky Way has an extensive gas halo that encircles it. This is made up of a hot gas and is thought to be up to thousands of light years in width. The mass of this halo is estimated to be equal or greater than all of the stars in the Milky Way put together. This halo also rotates with the movement of the galaxy. It does, however, move somewhat slower than the Milky Way itself. Previous theories stated that the gas halo stood still, but now we know that to be false.
The bulge in the center of the Milky Way is the densest area, filled with more gas, dust, and stars. The density of the center makes it impossible to see into it, or out to the other side. In the depths of the center of the Milky Way resides a supermassive black hole. This black hole is said to be billions of times more massive than our sun. It is possible that this black hole began much smaller and has grown due to the sufficient amount of dust and gas available for consumption. Stars are also a part of its diet. Black holes are thought to be a common part of the center of most galaxies. Scientists are able to locate them by observing the changes of the environment around them. The strong gravitational pull of a black hole changes the motion of the material around it. Jets are also fired off from time to time.
The Milky Way has many detailed elements that many of us have forgotten over the years. It can be fascinating to revisit the many mysteries of our universe and where Earth fits in. The details of the Milky Way help to explain a little bit about what you see when you peer out into the sky from our planet. Take a moment to think about the wonder that surrounds us.