Physics 103 fall 2001 Laboratory Exercise #6 – Part I galaxy classification purpose




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Group Name ________________________________ Section ______________________
Lab Partners: Date _____________________
PHYSICS 103

FALL 2001

Laboratory Exercise #6 – Part I


GALAXY CLASSIFICATION



Purpose: To develop a system by which to classify galaxies. To experience why classification is an important first step to understanding. To experience the difficulty with any classification scheme.

INTRODUCTION

When faced with a new kind of object, the first thing scientists usually do is describe what it looks like. Then they identify features that appear the same as or different from other members of the new class. Finally, they try to understand what causes these similarities and differences.


This activity encourages you to look at photographs of galaxies and to discover similarities and differences in the way they look. You will then sort the galaxies into different categories, based on what you see. Astronomer Edwin Hubble did essentially the same thing in the 1920s, when he devised a system for classifying galaxies by shape that proved extremely useful in helping us understand galaxies. His system is still widely in use, although it is being modified by new discoveries that indicate that galaxy shape depends greatly on the environment in which a galaxy is born.

PART 1: DEVISE A CLASSIFICATION




Instructions

On the following pages you will find images of 32 different galaxies. You will devise a scheme by which to classify the galaxies. First, look at all the galaxies. Ask yourself and your lab partners: What types of features do these galaxies possess? What are some similarities and differences between the different galaxies? Try to put the galaxies into classes or categories. YOU MAY SEPARATE THE IMAGES IF IT WILL HELP. Once you have placed the galaxies into categories, come up with names and descriptions of each category.






1) M31


2) M32


3) M49


4) M51




5) M59


6) M61


7) M64


8) M81





9) M82


10) M83



11) M84


12) M86




13) M87


14) M88


15) M89


16) M101




17) M104


18) M109


19) M110


20) Arp 252




21) LMC


22) Leo I


23) NGC 253


24) NGC 1302




25) NGC 1365


26) NGC 2146


27) NGC 3351


28) NGC 4565




29) NGC 4596


30) NGC 5383


31) NGC 6946


32) NGC 7743

On this page, describe your classification system. Be sure to give the name of each class and describe the properties each class does or does not posses. Be specific. If I give you another galaxy, you should be able to place it into a category based on these descriptions.


In the table below write the class each galaxy belongs to.


Galaxy

Class

Galaxy

Class

1) M31




17) M104




2) M32




18) M109




3) M49




19) M110




4) M51




20) Arp 252




5) M59




21) LMC




6) M61




22) Leo I




7) M64




23) NGC 253




8) M81




24) NGC 1302




9) M82




25) NGC 1365




10) M83




26) NGC 2146




11) M84




27) NGC 3351




12) M86




28) NGC 4565




13) M87




29) NGC 4596




14) M88




30) NGC 5283




15) M89




31) NGC 6946




16) M101




32) NGC 7743



When you reach this point, ask the instructor for Part 2 of the lab.

PART 2: CLASSIFY GALAXIES IN YOUR SCHEME
Below are images of two more galaxies. Next to each, write the name of the class in your scheme to which you would assign each galaxy.

NGC 1201

The Milky Way – Artist’s conception
When you reach this point, tell the instructor you are done and wait for Part 3.

PART 3: HUBBLE’S CLASSIFICATION SYSTEM


Astronomers have been using a classification scheme developed by Edwin Hubble in the 1920s. Read about this system in your textbook, chapter 15 pages 378-383. In the space below, write a brief description of each class of galaxy. Note: While the descriptions in the book are correct, some of the classifications given for specific galaxies are slightly off.

In the table below write the Hubble class each galaxy belongs to.


Galaxy

Class

Galaxy

Class

1) M31




17) M104




2) M32




18) M109




3) M49




19) M110




4) M51




20) Arp 252




5) M59




21) LMC




6) M61




22) Leo I




7) M64




23) NGC 253




8) M81




24) NGC 1302




9) M82




25) NGC 1365




10) M83




26) NGC 2146




11) M84




27) NGC 3351




12) M86




28) NGC 4565




13) M87




29) NGC 4596




14) M88




30) NGC 5283




15) M89




31) NGC 6946




16) M101




32) NGC 7743




NGC 1201




Milky Way



You have finally reached the end of the lab.





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