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Classifying Galaxies Correct answers are underlined. Content 1. What is a galaxy? a. a cloud of gas held together by momentum b. the empty space between stars c. billions of stars, dust, and gas held together by gravity d. planets revolving around a central star 2. Where are galaxies found? a. in the Milky Way b. all over the Universe c. in the Solar System d. near the Moon 3. What do galaxies look like? a. egg-shaped b. pinwheels c. spirals or ellipses d. spirals, barred spirals, or ellipses 4. Edwin Hubble classified galaxies according to their a. color b. shape c. temperature d. age 5. Which sequence of Hubble's class names is arranged from least elongated to most elongated? a. E0 E3 E5 b. E1 Sa SBa c. B0 S0 SBa d. E3 E2 E1 6. How are galaxies in  the classes Sa, Sb, and Sc, different? a. How bright they are b. The shape of the spiral arms c. They are different sizes d. The shape of the bright nucleus 7. What does it mean to classify something? Classifying a group of things or ideas means organizing them into sub-classes, based on some rule. For example, in Hubble's galaxy classification, elliptical galaxies were called class E, spirals class S, and barred spirals class SB.  One could also classify things by color or size, or any other rule that could be applied to all the items in the group. The Subject: 1. Would you like to learn more about astronomy? 2. What was one thing you learned that you didn't know before? 3. Would you like to learn more about Earth and Space Science? 4. Did you tell anyone outside the class about the internet lesson? Who?  What did you say? ©1997 The Regents of the University of California. Have a science question? Visit our Ask an Expert page. Email questions or comments about SEGway resources to: outreach@ssl.berkeley.edu