Galaxies! By: Mrs. Murray

A galaxy is a large collection of stars held together by gravity. What is a galaxy? A galaxy is a large collection of stars held together by gravity. http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000893.jpg

Galaxies may also contain large amounts of gas and dust. What is a galaxy? Galaxies may also contain large amounts of gas and dust.

Galaxies can contain billions of stars What is a galaxy? Galaxies can contain billions of stars

How are Galaxies Classified? Galaxies are classified by shape. http://www.nasa.gov/images/content/384664main_ero_stephan_quintet_4x3_946-710.jpg

How are Galaxies Classified? There are three main types of galaxies Spiral Elliptical Irregular http://www.nasa.gov/images/content/384664main_ero_stephan_quintet_4x3_946-710.jpg

How are Galaxies Classified? Each type of galaxy has its own characteristics. http://www.nasa.gov/images/content/384664main_ero_stephan_quintet_4x3_946-710.jpg

Spiral galaxies Spiral galaxies are a flat disc with a bulging center. The center is surrounded by spiral arms. http://www.nasa.gov/images/content/236088main_milkyway516.jpg

Spiral galaxies The spiral arms are a result of a spinning motion of the galaxy. The arms contain a large amount of gas and dust, therefore, many younger stars are found in the arms. http://www.nasa.gov/images/content/236088main_milkyway516.jpg

Spiral galaxies The bulge in the center is made up of mostly old stars. There are several types of spiral galaxies, including barred and sombrero. Our galaxy, the Milky Way, is a spiral galaxy. http://www.nasa.gov/images/content/236088main_milkyway516.jpg

Where in the Milky way do you think the sun is located?

Elliptical Galaxies Elliptical galaxies have an oval or egg shape. Elliptical galaxies contain very little gas and dust, and are therefore made up of mostly old stars. http://www.caelumobservatory.com/mlsc/m87crop.jpg

Elliptical Galaxies Stars in an elliptical galaxy move in random directions, not in a circular path like stars in a spiral galaxy. The largest galaxies in the universe are elliptical galaxies. http://www.caelumobservatory.com/mlsc/m87crop.jpg

Irregular Galaxies Irregular galaxies do not have a distinct shape like spiral or elliptical galaxies. Irregular galaxies are often misshapen because of the gravitational pull of nearby galaxies. http://www.nasa.gov/images/content/221073main_image_1055_946-710.jpg

sources http://science.nationalgeographic.com/science/space/universe/galaxies-article/