In this inquiry activity, students view NASA images of galaxies and develop a galaxy classification scheme.  Students then compare and contrast their classification scheme with that developed by Edwin Hubble. 

By completing this activity, the learner will: 

• recognize that galaxies are collections of billions of stars.
• understand that galaxies take a variety of forms.
• develop and apply a galactic classification scheme.
• comprehend that galaxies are classified in four major categories.

National Mathematics Education Standards

Materials and Technology

Scientific Background

Activity 1: Sort the galaxies by creating and applying a classification scheme based on appearance.

Activity 2: Sort the galaxies by using Edwin Hubble’s classification scheme. 

Debriefing: Evaluate your classification system along with Edwin Hubble's.

Although Immanual Kant first advanced the idea of "island universes" to explain the observed compact clouds during the eighteenth century, it wasn’t until this century that astronomers began to develop an understanding of the nature of galaxies.  Your instructor will provide you a sheet with fifteen galaxy photographs.  Your first task is to sort the galaxies by creating and applying a classification scheme based on appearance. Complete the table below.

Activity 2: Applying Hubble’s Classification Scheme

After you have completed Table 1, ask your instructor for a copy of Edwin Hubble’s classification scheme, which was developed in the 1920’s.  Complete the following table using his scheme. 

Question 2: Hubble viewed the tuning fork diagram as representing an evolutionary sequence for galaxies.  Using the tuning fork diagram, propose an evolutionary sequence for galaxies. 

Question 3: Astronomers now realize that the tuning fork diagram does not represent an evolutionary sequence.  Does this mean that Hubble’s scheme is useless?  Explain.