A Simple H-R Diagram

Once you know the luminosity and temperature (or color) of a star, you can plot the star as a point on the H-R diagram. Plot the luminosity on the y-axis with brighter stars going toward the top. Since brighter stars have lower magnitudes, if you choose to plot magnitude on the y-axis, the values will decrease as you go up. That's OK - just remember that the luminosity of the star is increasing.

Plot temperature on the x-axis. However, since you can't directly measure a star's temperature, you should instead plot color (such as b-v) on the x-axis. Traditionally, hotter stars have been placed at the left of the chart and cooler stars to the right. Even though the temperature decreases as you move the right, the b-v color values will increase. So you should make your H-R diagram with b-v increasing to the right.

The first H-R diagram you should try is a diagram for the brightest stars in the sky. The table below shows the 26 brightest stars in the sky. Instead of plotting their luminosities (which are so large that they're hard to visualize), plot each star's absolute magnitude. Absolute magnitude is defined as the magnitude that a star would have if you saw it from a distance of 10 parsecs (about 32 light-years). Stars with higher luminosities put out more light, so they are brighter - they have lower absolute magnitudes. Stars with lower luminosities put out less light, so they are dimmer - they have higher absolute magnitudes. Unlike apparent magnitude, absolute magnitude is determined only by the star's luminosity.

The table below shows the 26 brightest stars, giving their names, apparent magnitudes, absolute magnitudes, and b-v colors.

You can download the table as a CSV file, which you can save to your machine and open with Excel (some versions of Internet Explorer will open the file directly in the browser, in a new window).

If you want more stars, there is a list of the 314 brightest stars available here.