# Hertzsprung-Russell Diagram Activities

There are numerous excellent online and web-based activities related to the HR diagram. Some of these are listed below:

• Cluster Color-Magnitude Diagrams and the Age of Stars provides colour indices and magnitude data for the Pleiades and 47 Tuc, a globular cluster so that you can plot colour-magnitude diagrams and determine cluster ages.
• HR Applet (© McGraw Hill) is an online applet showing stellar evolution on the HR diagram. You can specify a star's parameters and watch it evolve. An evolutionary track is plotted. The site has accompanying explanations and background information.
• HR Diagram is an exercise that you can print out. It provides background theory and tables of bright and nearby stars for you to plot on the accompanying HR plot and frequency plot.
• HR Diagram Simulator allows you to place 1, 10 or 100 stars on the main sequence then compare their evolution off the main sequence either in steps or as a movie. Useful for demonstrating the concept of ZAMS.
• Jewels of the Night is an excellent and effective activity that you can download and printout. Students have to classify stars in this open cluster according to colour and magnitude. Has full instructions, worksheets, teacher guide and links.
• Nearest Stars is a handy list of the 50 nearest stars with several key properties such as parallax, spectral type and apparent and absolute magnitudes listed in table form. Follow the link to a second table listing the 50 Brightest Stars.
• NStars Database is a NASA with details on 2.600 stars within 25 pc. Fully searchable, provides professional-grade data and references.
• Stellar Evolution Simulation from Cornell allows you to alter the mass of a star and see how this affects its evolutionary track from the main sequence onwards. The results are plotted on a luminosity/temperature HR diagram in time steps with representations of star size. It comes with a useful set of instructions. Highly recommended.
• Table of Main Sequence Star Data is a concise set of examples of different spectral classes. There is also a table of the Nearest Stars to Earth.
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