animated image of observatory domeGalactic Inquiry

Overview

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. 

Learner Outcomes

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 Science Education Standards

National Mathematics Education Standards

Materials and Technology

Scientific Background

Teacher Lesson Plans

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.


Teacher Lesson Plans

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.  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.

Go back to Activities
Galaxy Classification Galaxy ID Numbers
Defining Characteristics
(provide enough detail so that anyone could use your scheme)
Category I Galaxy Classification Galaxy Classification
Category II Galaxy Classification Galaxy Classification
Category III Galaxy Classification Galaxy Classification
Category IV Galaxy Classification Galaxy Classification

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. 

Go back to Activities.
Hubble's Catagories Galaxy ID Numbers
Defining Characteristics
(provide enough detail so that anyone could use your scheme)
Category E Galaxy Classification Galaxy Classification
Category S Galaxy Classification Galaxy Classification
Category SB Galaxy Classification Galaxy Classification
Category Irregular Galaxy Classification Galaxy Classification


Lesson Debriefing

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. 

Go back to Activities.

Assessment
 
FACTS FOR STUDENTS
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]