Most galaxies are so far away that people can view them only with the help of telescopes. Only three galaxies can be seen with the unaided eye: the Andromeda Galaxy and the Large and Small Magellanic Clouds. These galaxies appear as cloudy patches in the sky. Other galaxies appear as fuzzy spots in the sky when viewed with small telescopes.
The shapes of galaxies vary: some are elliptical, others are spiral, and still others have no definite shape. Galaxies differ in color, composition, orientation, age, size, the number of stars within them, and their distance from Earth.
Galaxies are large collections of stars, gas, and dust held together by their gravitational attraction.
In fact, galaxies are dynamic and change over millions of years. Stars are born and die in galaxies. A galaxy also can interact with another galaxy, which alters both galaxies' shapes.
The size a galaxy appears to be to an observer depends on how many stars are in it and how far away it is. Two galaxies may appear to be the same size. One of them, however, may be a small galaxy close to Earth and the other a large galaxy that is much farther away.
"Myths vs. realities: Galaxies" contains common misconceptions about galaxies. The misconception is presented as the “myth” and an explanation of the true concept is the “reality.” Teachers should be aware of the misconceptions students harbor because they impede students' ability to see the “big picture” in the various sciences; hamper students' ability to apply science principles meaningfully to everyday life; and diminish students' ability to appreciate the links among science concepts and generalizations.
This resource aids teachers in identifying and remedying student misconceptions about galaxies. The best way to learn how students think is to ask them. Below are two strategies that can be employed to identify your students' misconceptions concerning galaxies. The first is an individual writing activity that allows students to think independently. The other is a group activity that allows students to share their ideas verbally.
An individual writing activity. To prepare for a study of galaxies, explain that you are interested in finding out what your students already know about this topic before you start. Ask students to write down what they know about galaxies and why they know it. For example, they may say galaxies are very large and can easily be seen in the night sky. Collect their papers and compile a list of misconceptions the students display in their writing.
The next day, start your unit by explaining that it is common for people — both children and adults — to have misconceptions about their world. Explain that you have a list of misconceptions that you would like to discuss with the class. You can read the misconceptions that appear on Myths vs. realities as well as the ones compiled from the students' papers. Ask the students to comment on the misconceptions and discuss the reality of the situation. If your students have misconceptions about galaxies that we haven't included on our list, you can send them to us through the Contact us section of this web site, and we'll add them to our list. You may want to make special mention of any new misconceptions the students revealed, and let them know you'll submit them to us for addition to our list.
• A group activity. Begin your study of galaxies by explaining to students that sometimes the ideas they have about this topic may not be entirely true, and that you are going to try to identify these ideas. Explain that some of these ideas are very hard to remove, and that even their parents may have some of these misconceptions Tell the students that you will read a statement (either a myth or a reality) and they must decide whether it is true or false. Ask them to explain their decision in writing.
Once students have written their responses, discuss their thoughts and the accuracy of the statement. Be sure to establish some ground rules concerning student responses to the thoughts of their peers. Remind them that almost anyone can hold these misconceptions, but they need to be identified and removed before true learning can begin. Ask students if they have any other misconceptions that are not covered in the activity, so you can submit them to us for addition to our list through the Contact us section of this web site. It might help students feel more invested in the activity.
Amazing Space resources by topic: Galaxies