Conclusion

You now know a great deal about what galaxies are, what they look like, and how they affect one another. But you can also study one more question: how do galaxies evolve through time? Hubble tried to solve this problem: he thought that galaxies evolved to the right on the tuning fork diagram. He was mistaken. Do you think you can figure out the answer to the problem that stumped Hubble?

Galaxy Evolution

This section will take a lot of time and effort, but it gives you the opportunity to solve the problem that Hubble couldn't solve! The Research Challenge below will guide you through your study. Do this section on your own, and take your time. Have fun with it. When you finish, E-mail us your diagrams and an explanation of what you found, We'll look at all the results we receive, and we'll put the best work up on this site!

The galaxy cluster you looked at in this project, Abell 2255, is at redshift 0.081. By looking at different redshifts, you look at different distances away from Earth (see the Hubble diagram project for more information). Because the speed of light is finite, when you look at larger distances, you are looking at things as they were in the more distant past. So by looking at galaxy clusters of different redshifts, you can see if galaxies have evolved over time.

One easy way to tell if galaxies have changed is to see if their colors have changed. The Research Challenge guides you in making a color-color diagram of galaxies at different redshifts. Can you think of other ways to study galaxy evolution?

Project designed by Robert Sparks

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