The Bridge V Learning Edition 1 ; our solar system | Page 57

Note: The smallest galaxies are often called dwarf galaxies (No. 5 and No. 7 are dwarf galaxies).
These contain only a few billion stars — a small number compared to the Milky Way's 200
billion. The largest ellipticals contain several trillion stars. Discuss: How does the classification
scheme used by astronomers compare with the classification schemes designed by members of
the class?
Step 4
Tell students: Use the image below and guidelines to help decide how to identify and count the
galaxies.
Guidelines:
ˆ I) Ellipticals or Lenticulars : it can be hard to tell these apart. If you know it's either an E
or S0 / SB0, it is okay to guess between these two.
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