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On this page you will find various resources and activities linked to observing and analysing stars.
Plotting a Hertzsprung-Russell Diagram
Plotting a Hertzsprung-Russell Diagram
In this project you will be shown how to use astronomical images to measure the intensity of light from the stars in a cluster (a process known as photometry), through different filters, and plot the colours of the stars on a 'colour-magnitude diagram' (the astronomer's version of a HR diagram). Once a measure of how “red” or “blue” the stars are is made, more information about them can be obtained– massive stars are usually very blue (hot), intermediate mass stars (like the Sun) are yellow, and the very lowest mass stars are red (cool).
LCS_Bkgrd_Info.pdfThis document gives some background information on Hertzsprung-Russell diagrams, Colour-Magnitude diagrams and open and globular clusters
photometry_salsaj_SR_points.docThis short document explains how to carry out photometry of star clusters using the free software package, SalsaJ, and then how to plot a colour-magnitude diagram either by hand or with the Excel spreadsheet, 'CMD plotter' below.
CMD_plotter_SR.xlsThis Excel spreadsheet is used to calculate the magnitudes of the stars in the star cluster from their intensities, and plots a colour-magnitude diagram with the results.
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