C.O.P.P.A The information you provide below will be used for internal purposes only. Glencoe/McGraw-Hill does not share information about you with organizations outside the family of The McGraw-Hill Companies. Before you supply any personal information below, please read our complete Privacy Policy.   Click the Techie Toolbox for tips and help to make the most of your time on the Web.   Chapter 31: Galaxies and the Universe   Classifying Galaxies Edwin Hubble developed rules for classifying galaxies according to their shapes as seen in telescopic images. Astronomers are interested in the classification of galaxies. This information can indicate whether a certain type of galaxy is more likely to form than another and helps astronomers unravel the mystery of galaxy formation in the universe. Using the resources of the Internet and sharing data with your peers, you can learn how galaxies are classified. Problem How can different galaxies be classified? Hypothesis How might galaxies be classified using Hubble's classification system? Are there absolute classifications based solely on shape? Form a hypothesis about how you can apply Hubble's galaxy classification system to galaxy images on the Internet. Objectives Gather and communicate details about galaxy images on the Internet. Form conclusions about the classification of different galaxies. Reconstruct the tuning-fork diagram with images that you find. Data Sources Activity links View Student Data Find a resource with multiple images of galaxies and, if possible, names or catalog numbers for the galaxies. The Activity Links lists sites that have galaxy images. Choose one of the following types of galaxies to start your classification: spirals, ellipticals, or irregular galaxies. Gather images and information, such as catalog numbers and names of galaxies, from the Activity Links or the library. Sort the images by basic types: spirals, ellipticals, or irregular galaxies. For each basic type, compare the galaxies to each other and decide which galaxy best represents each class and subclass of Hubble's galaxy classification system: Sa, Sb, Sc, SBa, SBb, SBc, S0, E0-E7, and Irr. Try to find at least one galaxy for each subclass. Arrange the galaxy images to construct a tuning-fork diagram like Hubble's. Complete the data table below. Add any additional information that you think is important. Visit sites listed in the Activity Links for information about other galaxies. Sharing Your Data Post your data in the table provided below for this activity. Use the additional data from other students to complete your chart and answer the Conclude & Apply questions. Were there any galaxy classes or subclasses that were difficult to find images for? If so, which ones? How many of each type of galaxy-normal spiral, barred spiral, elliptical, and irregular-did you find? Calculate the percentages of the total number of galaxies that each type represents. Do you think this reflects the actual percentage of each type of galaxy in the universe? Explain. Were there any galaxy images that you found that didn't fit your classification scheme? If so, why? Was it difficult to distinguish between a normal spiral and a barred spiral in some cases? Explain your method. What problems did you have with galaxies that are edge-on as seen from Earth? Ellipticals are usually a difficult type of galaxy to classify. Why? Results Classifying Galaxies Galaxy Name Classification Notes Galaxy Name Classification Notes Galaxy Name Classification Notes Galaxy Name Classification Notes Galaxy Name Classification Notes Galaxy Name Classification Notes Galaxy Name Classification Notes Galaxy Name Classification Notes Galaxy Name Classification Notes Galaxy Name Classification Notes * City: * State: Select Your State Alabama Alaska Arizona Arkansas California Colorado Connecticut Delaware District of Columbia Florida Georgia Hawaii Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Texas Utah Vermont Virginia Washington West Virginia Wisconsin Wyoming Not Applicable * School: * required