H-R Star Spectrum Lab
The H-R diagram, as it’s known for short, plots a star’s luminosity — its true brightness — against its surface temperature in Kelvin. Are there patterns that emerge and what does this data tell us as astronomers? In this lab we will investigate the relationship between the temperature, brightness and diameter of stars.
Procedure: Using the data below, plot the stars from Group 1. As you plot the stars, use the appropriate colored pencil. (OY = Orange Yellow, BW = Blue White, YW = Yellow White)
1. Once you have plotted the stars from Group 1, answer the Group 1 Questions. 2. Using the same graph, plot the stars from Group 2. 3. Once you have plotted the stars from Group 2, answer Group 2 Questions. 4. Using the same graph, plot the stars from Group 3. 5. Once you have plotted the stars from Group 3, answer the Group 3 Questions. 6. Refer to your textbook to label the following regions of your diagram- Main Sequence, Red Giants, White Dwarfs.
Apparent Distance Temperature Luminosity Group 1 Magnitude (light-years) (x 1000 Kelvin) (Sun = 1) Color 1. 61 Cygni A 5.19 11.1 4.2 0.084 R
2. 61 Cygni B 6.02 11.1 3.9 0.039 R
3. 70 Ophiuchi A 4.3 17 5.1 0.6 OY
4. Achernar 0.51 65 14 200 BW
5. Alpha -0.01 4.3 5.8 1.5 Y Centauri A 6. Alpha 1.4 4.3 4.2 0.33 O Centauri B 7. Alpha 11 4.3 2.8 0.0001 R Centauri C 8. Alpha Crucis 1.39 400 21 4,000.00 BW
9. Altair 0.77 16.5 8 11 W
10. Barnard's Star 9.54 6 2.8 0.00045 R
11. Beta Centauri 0.63 300 2.1 5,000.00 BW
12. Delta Aquarii 3.28 84 9.4 24 W A Answer on a separate piece of paper
13. Delta Persei 3.03 590 17 1,300.00 BW
14. Deneb 1.26 1,400.00 9.9 60,000.00 BW
15. Epsilon 3.73 10.8 4.5 0.3 O Eridani 16. Epsilon Indi 4.73 11.4 4.2 0.14 O
17. Fomalhaut 1.19 23 9.5 14 W
18. Lalande 21185 7.47 8.1 3.2 0.0055 R
19. Luyten 726-8 12.5 8.7 2.7 0.00006 R A 20. Luyten 726-8 12.9 8.7 2.7 0.00002 R B 21. Luyten 789-6 12.58 11 2.7 0.00009 R
22. Procyon A 0.38 11.3 6.5 7.3 W
23. Ross 128 11.13 11 2.8 0.00054 R
24. Ross 154 10.6 9.6 2.8 0.00041 R
25. Ross 248 12.24 10.3 2.7 0.00011 R
26. Sirius A -1.43 8.7 10.4 23 W
27. Spica 0.91 260 21 2,800.00 BW
28. Sun -26.7 0.00002 58 1 Y
29. Tau Scorpii 2.82 233 25 2,500.00 BW
30. Vega 0.04 26 10.7 55 BW
31. Wolf 359 13.66 7.7 2.7 0.00003 R
32. Zeta Persei A 2.83 465 24 16,000.00 BW Answer on a separate piece of paper
Distance Apparent (light- Temperature Luminosity Group 2 Magnitude years) (Kelvin) (Sun = 1) Color 33. Aldebaran 0.86 53 4.2 100 O
34. Antares 0.92 400 3.4 5,000.00 R
35. Arcturus -0.06 36 4.5 110 R
36. Betelgeuse 0.41 500 3.2 17,000.00 R
Distance Apparent (light- Temperature Luminosity Group 3 Magnitude years) (Kelvin) (Sun = 1) Color 37. Grw +70 8247 13.19 49 9.8 0.0013 W
38. L 879-14 14.1 63? 6.3 0.00068 W
39. Procyon B 10.7 11.3 7.4 0.00055 YW
40. Sirius B 8.5 8.7 10.7 0.0024 W
41. Van Maanen's 12.36 14 7.5 0.00016 W Star 42. W 219 15.2 46 7.4 0.00021 W
Answer on a separate piece of paper
.0001 .00001 Answer on a separate piece of paper
Questions: Group 1
1. What would you tell someone who thinks that all stars are very similar (be sure to discuss temperature and brightness)? 2. How does our sun compare to other stars in brightness and temperature? 3. Are the stars scattered randomly on the graph, or is there a pattern? Explain. 4. Would you expect hotter stars to be dim or bright? Does the graph agree with this answer? Group 2
5. Do the Group 2 stars follow the same pattern as the Group 1 stars that you plotted? Explain. 6. Overall, are the stars in Group 2 very bright or very dim? 7. Are these stars hot or cool compared to other stars? 8. Is the relationship of brightness to temperature for these stars puzzling, or does it make sense? Explain. Group 3
9. Compare the areas of the graph where the Group 2 and Group 3 stars are plotted. How are they different? 10. Overall, are the stars in Group 3 very bright or very dim? 11. Are these stars hot or cool compared to other stars? 12. Is the relationship of brightness to temperature for these stars puzzling, or does it make sense? Explain. Additional Questions 13. As you can see from the Group 1 stars, the cooler or hotter a star is, the brighter it will be. The Group 2 and Group 3 stars do not follow this pattern. Hence, there must be something besides temperature that can affect how bright a star is. Describe your own theory about these stars (Group 2 and Group 3). Why would their brightness not be strictly related to their temperature? 14. What is the "Main Sequence?" 15. What percent of all stars are on the Main Sequence? 16. Why aren’t the Group 2 and Group 3 stars on the Main Sequence? 17. Why might stars of one color be much more abundant than stars of another color? 18. Which type(s) of star should we consider first when looking for stars that might have life-supporting worlds around them? Why?