Galaxies and the Milky Way
You might be surprised to find out how many galaxies are in the universe. So many galaxies exist that they are observed in clusters like stars. These clusters of galaxies can vary in both size and density. Huge clusters with a high density are termed rich clusters. Your home galaxy, the Milky Way, is in a local group with a small density. This cluster is termed a poor cluster. Thanks to the Hubble Space Telescope, astronomers now estimate that the universe is made of hundreds of billions of galaxies!
Each one of these galaxies contains billions, if not trillions, of stars, gas, and dust all held together by gravity. Astronomers have classified the galaxies into three main shapes. Elliptical galaxies are shaped like an oval. Spiral galaxies have a central disk and winding arms. An irregular galaxy does not fit any shape at all! In this interactivity, learn about three different classifications of galaxies by clicking on each of the folder tabs. Click the player button to begin.
View a printable version of the interactivity.
To learn more about the birth and evolution of galaxies, view the video Evolution of the Universe from eMediaVA℠. As you view the video, consider the following question: Which formed first - stars or galaxies?
Galaxy Names
French astronomer, Charles Messier,
who published an astronomical catalog
Most galaxies are identified by a group of letters and numbers. These letters indicate the catalog listing of the galaxy. The galaxy could be listed in several different catalogs. The most common is NGC. This stands for New General Catalog. Other catalogs are listed below:
- M: Messier
- ESO: European Southern Observatory
- IRAS: Infrared Astronomical Satellite
- Mrk: Markarian
- UGC: Uppsala General Catalog
Numbers always follow the letters, such as NGC 3314. These numbers indicate the location of the galaxy in the sky, or when the galaxy was entered into the catalog. Also, galaxies can be entered into more than one catalog, so they can have more than one name.
The Milky Way Galaxy
The Milky Way Galaxy is home to the Solar System and to planet Earth. Scientists believe that this barred spiral galaxy began forming during the Big Bang. View this presentation for a brief introduction to the history, formation, location, and structure of the Milky Way Galaxy. Click the player button to begin.
View a printable version of the interactivity.
To see an animation of a voyage away from the Milky Way galaxy, and past other galaxies, view the video Galaxies from eMediaVA℠. As you view the video, make note of any structural or descriptive features of the Milky Way Galaxy that you learned about in this topic.
Galactic Morphology
Image courtesy of NASA
An artist's depiction of the collision of the
Andromeda Galaxy and the Milky Way Galaxy
Astronomers know that galaxies are moving in space. Some galaxies are shifting away from the Milky Way while others are moving towards our galaxy. With all of this shifting, collisions are bound to take place. The interaction of two galaxies is termed galactic cannibalism. Generally when this happens the two galaxies merge together to form a larger, irregular-shaped galaxy. Will our galaxy ever collide with its neighbors? Astronomers think the answer is "yes." The larger Andromeda galaxy and the Milky Way may collide in a few billion years. Both galaxies are spiral in shape and the resulting collision will create an elliptical galaxy.
Galaxies and the Milky Way Review
Check your knowledge of galaxies and the Milky Way Galaxy in this non-graded activity. Read the directions associated with each question and select the correct response. Then, click SUBMIT to check your responses. Click the player button to get started.