Planets, Stars, Galaxies, and the Universe

Lab 2, Part 1



HR diagrams, or color magnitude diagrams, really are essential tools in the study of stars. I could find many examples in the astronomical literature, but will ask you to compare the following

  1. Early HR diagram by Russell (1914)
  2. 9 million star CMD (1999)

The first is a diagram by H.N. Russell from a publication in 1914, and the latter is a diagram from about 80 years later that includes data on 9 million stars. By studying these diagrams in depth, both studies (and many others) have helped astronomers piece together the story of stellar evolution.

It is a useful exercise to create and study your own HR diagrams. During this second lab exercise, you will be asked to create several. At all times, you should recall the quantities that are typically plotted (color, temperature, or spectral type on the x-axis and luminosity, apparent brightness, absolute magnitude, or apparent magnitude on the y-axis) and the typical orientation of the axes (blue or hot on the left, red or cool on the right, faint on the bottom, bright on the top).

We will follow along the lab that is posted on the Sloan Digital Sky Survey (SDSS) Sky Server page (linked below), but I will alter some of the directions and questions.


NOTE: You will be submitting this lab as a single document that is in either Microsoft Word (.doc) or PDF (.pdf) format so I can open it.

Since there are a variety of ways you may create your HR diagrams, you will need to consider how you will incorporate it into your submitted document. I suggest you either save it first as a graphics file (.jpg, .pdf, or .tiff) which you then paste into your document.

  1. For part 1 of this lab, go to the HR diagram lab at the SDSS Sky Server website.
  2. Read pages 1 & 2.
  3. Follow the instructions on page 3 ("Exercise 1") to create an HR diagram using the data provided on the 26 brightest stars. (Feel free to add stars from the longer table of 314 brightest stars if you prefer, but this is not required.)

    NOTE: You do not have to submit answers to the questions that are posted on the lab website, but you can certainly consider how you might answer them or record answers if you want to do so for your own benefit.

  4. Go on to page 5 and follow the instructions to make an HR diagram for the 26 nearest stars ("Exercise 2"). Again, you do not have to submit answers to the questions that are posted there.
  5. Save your work, as we'll continue this in part 2 (Lesson 7)!