Objective : To study the relationship between the temperature and true brightness of stars (discovered in the 1910's by Ejnar Hertzsprung of Denmark and Henry Norris Russell of the USA). A star's temperature is measured by either color or spectral class while its intrinsic brightness is measured as absolute magnitude.
Procedure : Draw axes (left = short side, bottom = long side) on the graph paper. Draw the axes only a few boxes from the edge of the paper. The vertical axis on the left will be Absolute Magnitude. Make the top of the absolute magnitude scale be -8 and make the bottom +20 with one number per line. The bottom axis will be Spectral Class. Label the left end O0, then O2,O4,O6,O8,B0,B2, etc, ending with M8. Remember that the spectral class sequence is O B A F G K M.
Plot the dots in Table 1 with one color of pencil, the dots in Table 2 with another color or another symbol. Remember to label the axes "Absolute Magnitude" and "Spectral Class". Do not label the stars by name and do not connect the dots or symbols.
Include a small legend to identify the symbols for Table 1 (Near) and Table 2 (Bright).
| Star Name | Ab.Mag. | Sp.Class | Star name | Ab.Mag. | Sp.Class |
| Sun | 4.85 | G2 | e Eridani | 6.2 | K2 |
| Proxima(aCen C) | 15.5 | M5.5 | Lacaille 9352 | 9.8 | M1.5 |
| a Centauri A | 4.4 | G2 | Ross 128 | 13.5 | M4 |
| a Centauri B | 5.7 | K0 | EZ Aquarii | 15.6 | M5 |
| Barnard's Star | 13.2 | M4 | Procyon A | 2.7 | F5 |
| Wolf 359 | 16.6 | M6 | Procyon B | 13.0 | A0 |
| Lalande 21185 | 10.4 | M2 | 61 Cygni A | 7.5 | K5 |
| Sirius A | 1.5 | A1 | 61 Cygni B | 8.3 | K7 |
| Sirius B | 11.3 | A2 | Gliese 725 A | 11.2 | M3 |
| UV Ceti A | 15.4 | M5.5 | Gliese 725 B | 12.0 | M3.5 |
| UV Ceti B | 15.9 | M6 | Gliese 15 A | 10.3 | M1.5 |
| Ross 154 | 13.1 | M3.5 | Gliese 15 B | 13.3 | M3.5 |
| Ross 248 | 14.8 | M5.5 | e Indi | 6.9 | K5 |
Reference: Henry, T., http://joy.chara.gsu.edu/RECONS/TOP100.htm, 2002 _______________________________________________________________________
| Star Name | Ab.Mag. | Sp.Class | Star name | Ab.Mag. | Sp.Class |
| Sun | 4.85 | G2 | Betelgeuse | -5.0 | M2 |
| Sirius | 1.5 | A1 | Achenar | -2.9 | B3 |
| Canopus | -5.4 | A9 | Hadar | -5.5 | B1 |
| Arcturus | -0.6 | K2 | Altair | 2.1 | A7 |
| Rigel Kent(a Cen) | 4.2 | G2 | Aldebaran | -0.8 | K5 |
| Vega | 0.6 | A0 | Spica | -3.6 | B1 |
| Capella | -0.8 | G6 | Antares | -5.8 | M1.5 |
| Rigel(900 ly.) | -6.6 | B8 | Formalhaut | 1.6 | A3 |
| Procyon | 2.8 | F2 | Pollux | 1.1 | K0 |
Reference: Pasachoff, J., Filippenko, A., The Cosmos, 2001
This page is http://csam.montclair.edu/~west/HRdiagram.html
Last updated April 10, 2002