Loading...

ASTR101: Introduction to Astronomy

Unit 10: The Properties of Stars   In this unit, you will be introduced to the properties of stars and how they are determined.  You will learn about the Hertzsprung-Russell diagram, one of the most important tools we have for understanding the evolution of stars, the topic for the next unit.

Unit 10 Time Advisory
This unit should take approximately 11 hours to complete.

☐    Subunit 10.1: 3 hours

☐    Subunit 10.2: 3 hours

☐    Subunit 10.3: 3 hours

☐    Assessment: 2 hours

Unit10 Learning Outcomes
Upon successful completion of this unit, students will be able to: - List the important properties of the sun along with the range of these properties in other stars. - Describe the conditions at the center of the sun in terms of temperature, chemical composition, and state of ionization. - Define apparent brightness and luminosity and describe the relationship between these two properties and distance to the star. - Draw a typical Hertzsprung-Russell diagram and label the axes. - Place stars with specific properties in the appropriate locations on the Hertzsprung-Russell diagram.

10.1 The Sun, an Average Star   - Reading: The Saylor Foundations “Unit 10: The Properties of Stars” Link: The Saylor Foundations “Unit 10: The Properties of Stars” (PDF)

 Instructions: This article provides an overview of the material we
will cover in Unit 10.  Read it carefully, but please don’t think
that you have to fix every single fact into your memory.  What you
should strive for is to be sure that it makes sense to you as you
are reading it and that when you are finished you can briefly
summarize the main points of the reading.  You should read this both
as you start and after you have finished working your way through
the unit.  

 Reading this article should take approximately 45 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.
  • Reading: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “The Solar Composition” Link: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “The Solar Composition” (HTML)

    Instructions: This article discusses the abundances of elements in the sun and the discovery of helium.

    Reading this article should take approximately 10 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Reading: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “Ionization and Plasmas” Link: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “Ionization and Plasmas” (HTML)

    Instructions: The interior of the sun is so hot that the atoms are completely ionized.  This article will help you understand the structure of the sun’s interior that allows for hydrogen fusion, the topic of the next section, to occur.

    Reading this article should take approximately 15 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Reading: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “The Harvard Spectral Sequence” Link: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “The Harvard Spectral Sequence” (HTML)

    Instructions: This article discusses the spectral classes of stars.

    Reading this article should take approximately 10 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

10.2 Distance, Apparent Brightness, and Luminosity   - Reading: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “The Parallax Method” Link: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “The Parallax Method” (HTML)

 Instructions: This article shows a diagram of the parallax method
and discusses the limitations of the method.  

 Reading this article should take approximately 10 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.
  • Reading: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “Units for Stellar Distances” Link: The University of Tennessee, Knoxville’s Department of Physics and Astronomy: “Units for Stellar Distances” (HTML)

    Instructions: This article defines two units used in astronomy, the light-year and the parsec.  Read over both, but for the purposes of this course, we will only use the light-year.

    Reading this article should take approximately 10 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Reading: Castle Rock High School: Carl Stello’s “Luminosity and Apparent Brightness” Link: Castle Rock High School: Carl Stello’s “Luminosity and Apparent Brightness” (HTML)

    Instructions: This article discusses the inverse-square law as it applies to the luminosity and apparent brightness of stars.  The last part of the reading discusses the magnitude scale that is sometimes used in astronomy to quantify the apparent brightness of stars.  You may want to read this, but it is not a concept that we will use in this course.

    Reading this article should take approximately 20 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

10.3 The Hertzsprung-Russell Diagram   - Reading: The University of Oregon: Davison E. Soper’s “Hertzsprung-Russell Diagram” Link: The University of Oregon: Davison E. Soper’s “Hertzsprung-Russell Diagram” (HTML)

 Instructions: This is a good introduction to the H-R diagram.  It
provides links to other topics that may be of interest to you.  

 Reading this article should take approximately 15 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.
  • Reading: Cornell University: Martha Haynes’ “Astronomy 2201: Hertzsprung-Russell Diagram” Link: Cornell University: Martha Haynes’ “Astronomy 2201: Hertzsprung-Russell Diagram” (HTML)

    Instructions: This is a brief discussion of the H-R diagram that has a nice illustration showing the colors of the stars in the various regions of the diagram.

    Reading this article should take approximately 10 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Web Media: University of Nebraska, Lincoln’s Nebraska Astronomy Applet Project: “Hertzsprung-Russell Diagram Explorer” Link: University of Nebraska, Lincoln’s Nebraska Astronomy Applet Project: “Hertzsprung-Russell Diagram Explorer” (HTML)

    Instructions: This is an interactive link.  It will allow you to vary surface temperature and luminosity for stars and see what they look like in size and color relative to the sun.  It will also allow you to pick categories of stars to see where they appear on the H-R diagram.

    Exploring this resource should take approximately 20 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Assessment: The Saylor Foundation’s “Unit 10 Assessment” Link: The Saylor Foundation’s “Unit 10 Assessment” (PDF)

    Instructions: When you have finished the entire unit, please complete this assessment without referring to the readings.  When you are finished with the assessment, you can check your answers against the Saylor Foundation’s “Unit 10 Assessment – Answer Key” (PDF).

    Completing this assessment should take approximately 2 hours.