# How to use the HR diagram

Initial Publication Date: June 29, 2009

## Summary

In this astronomy activity students plot data on the Hertsprung-Russel diagram, the standard graphical method of comparing stars. After plotting the data they make conclusions about nature of the category to which the star belongs, thier relative ages, and the life-cycle stage each star is in.

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## Learning Goals

- Stellar evolution.
- Data processing and analysis.

## Context for Use

This activity typically takes an hour or so and is adaptable to a laboratory or classroom. To prepare for this activity students need to have some prior lesson in stellar evolution.

## Description and Teaching Materials

- Blank HR diagram (Excel 2007 (.xlsx) 17kB Sep29 09)
- Stellar Data (Microsoft Word 2007 (.docx) 19kB Jun29 09)

## Teaching Notes and Tips

As students are plotting the data it is important to make sure they carefully plot the data points. Sloppy hand graphing will yield poor results. Also, the luminosity in the data tables are given in decimal numbers whereas the HR diagram luminosity is in power of ten notation so there is good practice here in converting between decimal numbers and scientific notation. It also a good lesson in how to round a number in scientific notation to a number in power of ten notation.

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The activity described here is only a graphing exercise. It should be followed by questions that require students to interpret their data. This is how I routinely assess this activity, with follow-up questions that ask, for example, students to identify which stars are main-sequence, giants, dwarfs. Among the giants, which stars are likely to end as a planetary nebula, or a super-nova explosion?