University of Michigan - Department of Astronomy

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Stellar Evolution

Whirl on, giant clouds of gas; may you reach a threshold mass.
Protostars and blobs and dots, form within your glowing knots;
Whirl on, giant clouds of gas; may you reach a threshold mass.

--Pietro Calogero (a new verse for Twinkle Twinkle Little Star)

Overview.

Introduction

Stars spend 90% of their lifetime on the Main Sequence, but in the last 10% of their lives, their life tracks take them to other parts of the Hertzsprung-Russell Diagram. The stars change dramatically in temperature, luminosity, and size. They also produce some fascinating end-products in these late evolutionary stages.

Theories of stellar evolution were originally founded on  a few optical observations and some physics and chemistry.  These  initial models were difficult to confirm when they were first  developed.  However, modern observations, like the discovery of a supernova in the Large  Magellanic cloud in 1987, have advanced our understanding of  stellar evolution into a true scientific theory. Our understanding comes from a mixture of images at many different wavelengths as well as data, such as light curves. The Hertzsprung-Russell (H-R) diagram is a useful tool for organizing our information. We can trace the changes in luminosity and surface temperature over time on an H-R diagram.  In this lab you will look at a number of pictures, including multi-wavelength images and illustrations.  Your goal will be to identify the images and put them in place on an H-R diagram.

You can get a pdf with the images here


Images and the H-R Diagram

You have two H-R diagrams, one labeled "High Mass" (roughly 50 Msun) and one labeled  "Medium Mass" (2 Msun).  An appropriate evolutionary track is drawn on each, with several points labeled.

Begin by identifying each of the pictures.

Write a concise description in table 1 in the row with the picture number. 

Identify which image belongs with each label on the H-R diagram.  Record the letter in table 1. Make sure your description in table 1 makes it clear why the image belongs in that position.  All the letters must be used, and places with two letters indicate two images. Some of the images may be used for both high and medium mass stars.

Table 1
#
Letter(s)
Description
1
   
2
   
3
   
4
   
5    
6    
7    
8    
9    
10    
11    
12    
13    
14    
15    
16    


Diagrams



Last modified: 9/15/06

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