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The Hidden Lives of Galaxies - Classroom Activities

Activity #3 - Classifying Galaxies Using Hubble's Fork Diagram

In this activity, students explore the idea of classifying objects. They start by giving examples of objects that can be classified in everyday life and in science. They then characterize and classify a set of galaxies using their own scheme, and using Hubble's classification scheme.

See Student Worksheet

Note that the Galaxy Classification Chart is on the "Hidden Lives of Galaxy" poster and is available as Transparency #4 - Galaxy Classification Images. Transparencies are available at

Worksheet Answers/Assessment Guide
Part 1

  1. We put objects into categories to help us organize the items, and to identify similarities. By putting items in different categories, we can identify their differences.
  2. Examples of items we categorize in everyday life may include a CD collection, clothes, magazines, books. An example of how classifying helps organize one's life may be that an organized CD collection makes it easier to locate music by artist name or music type. Classifying objects into categories helps us identify similarities in their properties and/or their functions. Examining a group of similar objects together helps scientists determine the reasons or causes behind their properties or behavior.
  3. Scientists classify the different elements (through the periodic table), different forms of life (through kingdoms, species, etc.), different types of stars, as just a few examples.

Part 2

  1. Below are the names given to these galaxies by astronomers (hopefully your students came up with better names!), the galaxy type, and galaxy classification using the Hubble Fork Diagram.

Galaxy Classification Chart


A service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA/GSFC

NASA Logo, National Aeronautics and Space Administration