# Assignment 6 for astrology.pdf - Rowan Introduction to...

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Rowan Introduction to Astronomy Activity #6: Properties of Stars: The Hertzsprung-Russell Diagram Name: _______________________________________________ Score: ____________________________________ Acknowledgement This activity is adapted from “ The Life Cycles of Stars ” developed for Project ASTRO NOVA by the Planetarium at Raritan Valley Community College (The New Jersey Astronomy Center for Education at Raritan Valley Community College, Somerville, NJ 08876 1265). Objective Students learn about these important properties shared by all stars: luminosity (brightness), temperature, and color. Background In the early 20 th century (around 1910), Swedish astronomer Ejnar Hertzsprung and American astronomer Henry Norris Russell plotted the colors (temperatures) of stars against their luminosities (or brightness). The resulting graph represented a huge leap forward in understanding stellar evolution, or the lives of stars. The color and temperature of stars are usually plotted on the x- axis, with high temperatures to the left and low to the right. All temperatures are given in K, or Kelvin degrees. Luminosity (usually plotted on the vertical or y- axis) is given in terms of the Sun’s lumi nosity (either multiples or a fractional part). Sometimes luminosity is replaced by the absolute magnitude of the star. Celestial objects appear in a vast range of brightness. For example our Sun appears 16 trillion times brighter than the faintest stars visible to the naked eye. Clearly, some other means of expressing astronomical brightness is needed. Astronomers have developed what is called the magnitude scale : a logarithmic scale in which a difference of exactly 5 magnitudes corresponds to a factor of 100 in brightness. Each magnitude corresponds to a factor of 2.512 in brightness because 2.512 × 2.512 × 2.512 × 2.512 × 2.512 = 100. The magnitude scale runs from large positive numbers for very faint objects to negative numbers for very bright objects. For example a star of magnitude 5 is 100 times fainter than a star of magnitude 0. A star of magnitude 1 is 2.512 times brighter than a star of magnitude 0. Your H-R diagram will use magnitudes. Construct a Hertzsprung-Russell Diagram [40 pts] I NSTRUCTIONS FOR I NDIVIDUAL H-R D IAGRAM