ASTR1120-001

HOMEWORK #2

DUE MONDAY February 21

Hertzsprung-Russell Diagram

Prologue

In this homework you will download a partially completed data sheet similar to the tables on pages A-12 and A-13 in your textbook and capture it into an Excel spreadsheet. Using equations from the lesson you will fill in some missing data and use Excel to plot an H-R diagram from what you have calculated. Finally, you will answer some questions regarding the data on the spreadsheet. The HR diagram you plot will be a useful tool for answering the questions.

  • READ ALL INSTRUCTIONS CAREFULLY AS YOU GO; DO NOT GLOSS OVER PAGES. IF YOU FOLLOW THE LINKS AND PAY ATTENTION TO WHAT YOU READ, EVERYTHING YOU NEED TO KNOW IS ON THESE PAGES.
  • For this assignment you will need the following:
    1. Floppy disk
    2. Access to a computer with spreadsheet software
    3. Familarity with Lesson 4, especially the sections on Brightness and Radii.
  • If you feel comfortable with the material and working with spreadsheets, you can probably do the whole assignment and print out a copy in one sitting so you won't absolutely need the floppy. We highly recommend that you do get one anyway to save your work on. Computers crash, homeworks get lost, etc.
  • You do not have to do the assignment on a computer. You may do all or some the calculations and graphing by hand if you wish, but this may take a long time. Even with zero familiarity with spreadsheet software and a massive fear of working with computers, figuring out the spreadsheet will probably be faster.
  • As you work, SAVE FREQUENTLY! Accidents happen to everyone but even if the computer crashes completely, you only lose as much work as since the list time you typed "Command-S" ("Ctrl-s" on a PC)1.
  • If you have just made a major change that you are uncertain about, you can use the "Save-as" command under the pull-down File menu so your unaltered material still exists on disk.
  • As you calculate values, it is worthwhile to do a "reality check" on the numbers you are generating to see if they are reasonable. For instance, if the B and O stars all have absolute magnitudes suggesting they are dimmer than the Sun, you may want to scrutinize the formula you entered in those cells!
  • Turn in a hard copy of the filled in spreadsheet and your graphs and answers to the questions.

Now that you are ready, let's get started!

  1. Download the Stellar Data File
  2. Open the file as a spreadsheet
  3. Calculate Absolute Bolometric Magnitudes and make an HR diagram using all the stars
  4. Calculate the Stellar Radii
  5. Answer the Questions
  6. Print out your spreadsheet and HR diagram and the questions. Staple it all together and turn it in in class. Loose (unstapled) homeworks risk having parts lost!