HR Diagram

HR Diagram – Student Guide Background Information Work through the background sections on Spectral Classification, Luminosity, and the Hertzsprung-Russell Diagram. Then complete the following questions related to the background information. Question 1: The table below summarizes the relationship between spectral type, temperature, and color for stars. Note that the surface temperature of the stars in the table increases. Question 2: Complete the following table related to stellar luminosities in solar units using the equation 2 4 L R T  . NAAP – HR Diagram Explorer 1/9 Star Surface Temperature K Spectral Type Color Betelguese 3530 M2 Red Arcturus 4,300 K5 Orange Sun 5830 G2 Yellow Procyon A 6530 F5 Yellow-White Sirius A 9145 A1 White Rigel A 11,000 B9 White Delta Orionis 33200 O9 Blue Radius (R ⊙ ) Temperature (T ⊙ ) Luminosity (L ⊙ ) 1 1 1 1 2 16.8 3 1 9 1 1/2 .057

Question 3: The mass luminosity relation 3.5 L M  describes the mathematical relationship between luminosity and mass for main sequence stars. It describes how a star with a mass of 2 M ⊙ would have a luminosity of ______11.31371_______ L ⊙ while a star with luminosity of 3,160 L ⊙ would have an approximate mass of _______10_________ M ⊙. HR Diagram Explorer Open the HR Diagram Explorer . Begin by familiarizing yourself with the capabilities of the Hertzsprung-Russell Diagram Explorer through experimentation.  An actual HR Diagram is provided in the upper right panel with an active location indicated by a red x. This active location can be dragged around the diagram. The options panel allows you to control the variables plotted on the x-axis: (temperature, B- V, or spectral type) and those plotted on the y-axis (luminosity or absolute magnitude). One can also show the main sequence, luminosity classes, isoradius lines, or the instability strip. The Plotted Stars panel allows you to add various groups of stars to the diagram.  The Cursor Properties panel has sliders for the temperature and luminosity of the active location on the HR Diagram. These can control the values of the active location or move in response to the active location begin dragged. The temperature and luminosity (in solar units) are used to solve for the radius of a star at the active location.  The Size Comparison panel in the upper left illustrates the star corresponding to the active location on the HR Diagram. Note that the size of the sun remains constant. NAAP – HR Diagram Explorer 2/9

Exercises  Drag the active location around on the HR Diagram. Note the resulting changes in the temperature and luminosity sliders. Now manipulate the temperature and luminosity sliders and note the corresponding change in the active location. Question 4: Check the appropriate region of the HR diagram corresponding to each description below.  Drag the active location around on the HR Diagram once again. This time focus on the Size Comparison panel. Question 5: Check the appropriate region of the HR diagram corresponding to each description below.  Check show isoradius lines. Note that at each point on a green line, stars have the same value of radius. Use these isoradius lines to check your answers in the table above. NAAP – HR Diagram Explorer 3/9 Description Top Right Bottom Left Hot stars are found at the: X Faint stars are found at the: X Luminous stars are found at the: X Cool stars are found at the: X Description Upper Left Upper Right Lower Right Lower Left Large Blue stars are found at the: X Small Red stars are found at the: X Small Blue stars would be found at the: X Really Large Red stars are found at the: X