Galaxy Activity

Activity 1: Developing a Classification Scheme

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.  

Task #1: Your first task is to sort the 15 galaxies on this sheet  by creating and applying a classification scheme based on appearance. 

Copy and complete a larger version of this table below in your lab notebook. Make it big enough to write details in!

Galaxy ClassificationGalaxy ID Numbers
Defining Characteristics 
(provide enough detail so that anyone could use your scheme)
Category IGalaxy ClassificationGalaxy Classification
Category IIGalaxy ClassificationGalaxy Classification
Category IIIGalaxy ClassificationGalaxy Classification
Category IVGalaxy ClassificationGalaxy Classification

Activity 2: Applying Hubble’s Classification Scheme

After you have completed Table 1, Click on and read Edwin Hubble’s classification scheme, which was developed in the 1920’s.  Complete the following table in your lab notebook using his scheme. 

Hubble's CatagoriesGalaxy ID Numbers
Defining Characteristics 
(provide enough detail so that anyone could use your scheme)
Category EGalaxy ClassificationGalaxy Classification
Category SGalaxy ClassificationGalaxy Classification
Category SBGalaxy ClassificationGalaxy Classification
Category IrregularGalaxy ClassificationGalaxy Classification

Questions to Answer in Lab Notebook

Question 1: Unless there is an underlying model, classification systems are completely arbitrary as long as the defining characteristics are clear to everyone.  Which of the two systems, yours or Hubble’s, does your group prefer?  Why? 

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. 

Early in the history of the universe, matter, primarily the light atoms hydrogen and helium, clumped together by gravitational attraction to form countless trillions of stars.  Billions of galaxies, each a gravitationally bound cluster of billions of stars, now form most of the visible mass in the universe. [9-12]