Conclusion
Modern astronomers have refined Hubble's classification scheme to
include more information about galaxies. However, the modern
classification system is still based on the Hubble tuning fork.
Now that you know how to classify galaxies, you are ready to use
your knowledge to learn something about what galaxies are like.
Below are some ideas for further exploring galaxies in the SDSS data.
Choose one, then search through the SDSS data to answer the questions. The
Navigation Tool
and the SQL Search Tool
will help you find galaxies; see the
Searching for Data tutorial to learn how to use the SQL Search tool.
When you finish your research project,
E-mail us your results, including all your graphs and the
object IDs you used to make them. We will look over all the results
we receive, and we will put the best of them up on these pages!
Exercise 5.
To prepare for the Research Challenge, make a color-color diagram for a large number of galaxies. Plot u-g
on the y-axis and g-r on the x-axis. On your diagram, label each
galaxy by its type. Try to identify the areas where different types of
galaxies lie on the color-color diagram. Try to come up with
rules that will tell you what type of a galaxy you are observing based
on its colors. You may want to make other color-color diagrams
(such as g-r on the y-axis and r-i on the x-axis) as well. |
Research Challenge. The following
table contains the redshifts and celestial coordinates of several galaxy
clusters. Can you see any differences in the clusters, or the galaxies that
make them up, at different redshifts? You may need to make color-color diagrams
of several clusters and compare them. Do you notice any
differences between rich clusters (with many galaxies) and poor
clusters (with few galaxies)?
Click on the Cluster name to launch the Navigation Tool focused on that
cluster.
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