8B30.20 - HR Diagram

Credit for the picture and explanation: ESO ( European Southern Observatory).
Credit for the picture and explanation: ESO ( European Southern Observatory).
Code Number:
Demo Title:
HR Diagram
Area of Study:
Stellar Astronomy

Credit for the picture and explanation:  ESO ( European Southern Observatory).  

In the Hertzprung-Russell diagram the temperatures of stars are plotted against their luminosities.  The position of a star in the diagram provides information about its present stage and its mass.  Stars that burn hydrogen into helium lie on the diagonal branch, the so-called main sequence.  Red dwarfs like AB Doradus C lie in the cool and faint corner.  AB Dor C has itself a temperature of about 3,000 degrees and a luminosity which is 0.2% that of the Sun.  When a star exhausts all the hydrogen, it leaves the main sequence and becomes a red giant or a supergiant, depending on its mass (AB Doradus C will never leave the main sequence since it burns so little hydrogen).  Stars with the mass of the Sun which have burnt all their fuel evolve finally into a white dwarf (left low corner).

  • H. Hauptmann, F. Herrmannm and K. Schmidt, "The Transformation of a Main Sequence Star into a Red-Giant Start in the Core-and Shell Model", TPT, Vol. 68, # 5, May 2000, p. 421.
  • Christopher L. Mulliss, "Teaching the Main Sequence", TPT, Vol. 34, # 6, Sept. 1996, p. 327.
  • Emilia P. Belserene, "Response", TPT, Vol. 27, # 4, April 1989, p. 231. 
  • David L. Mott, "Aging Stars", TPT, Vol. 27, # 4, April 1989, p. 231. 
  • Emilia Pisani Belserene, "Can We Watch the Stars Grow Older?", TPT, Vol. 25, # 7, Oct. 1987, p. 420.
  • Henry Albers, "It's the Temperature, Not the Composition", TPT, Vol. 18, # 1, Jan. 1980, p. 10.
  • Claudine Carlton, "Stellar Evolution and Cosmology in High School Physics", TPT, Vol. 17, # 7, Oct. 1979, p. 460. 
  • Robert T. Deck, "Comments on 'Why is the Sun So Large?'", AJP, Vol. 74, # 1, Oct. 2006, p. 10.
  • D. J. Mullan, "Why is the Sun So Large?", AJP, Vol. 74, # 1, Jan. 2006, p. 10.
  • H. Hauptmann, F. Herrmann, K. Schmidt, "The Transformation of a Main Sequence Star Into a Red - Giant Star in the Core - Shell - Model", AJP, Vol. 68, # 5, May 2000, p. 421.
  • M. Maercker et al., "Deciphering a Star's Spiral Shell", Back Scatter, Physics Today, Dec. 2012, p. 92.
  • D. Tattersfield, "7.25, The Hertzsprung-Russell Diagram", Projects and Demonstrations in Astronomy, p. 171.
  • Janice VanCleave, "Demonstrate Why Stars of the Same Luminosity Can Appear to Be of Different Brightness", Super Science Challenges, p. 15.
  • Janice VanCleave, "Winter Colors", Constellations for Every Kid, p. 208.

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.