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Astronomy 1103 Laboratory Manual Lab Section Date Name Exercise 1 For the first pan of this exercise you will use the HR Diagram for questions 1-10 (see Figure 1). It shows the main-sequence line and a number of main-sequence stars. Look at the horizontal axis of the HR diagram. Moving from left to right is the temperature increasing or decreasing? 2. Compare the Sun and the star 61 Cygni. Which star is redder in color? Explain. (o L CM 30b Vcca-L%--e- 3. How would you characterize the luminosity and temperature of the star Vega compared to the Sun? is more OJ'1d 1004-(-c than OOc Sun 4. Notice the Sun's position on the HR diagram. Imagine a future astronaut observing the Sun from an Earth-like planet 10 parsecs from our Solar System. Describe the Sun's appearance in that planet's night sky? Explain your reasoning. Sun WöU1d hoeJC ov would be os scy on CD DU( L 5. If the Sun and the star Kruger 60B side by side in space which star would be brighter (more luminous)? Tyu sun Determine the approximate numerical brightness difference between these two stars using Table 2. Show your work, 15 6 VOU PO or 19 C IS OIVOUt IPOD thwn (J. Page 56

The H-R Diagram 6. Now compare the Sun and the star HD 199579, Which one of these stars is brighter and by how much? wovlÅ (0300 \0tYiowS4ha-n Plot each one of the stars shown below on the HR Diagram (Figure 1). Place a small circle around each point and label the point with the star's name. Star Arcturus K2 -0.3 0.0 Aldebaran -0.7 Pollux 7. Why don't these stars lie on the main sequence? Explain. All be \JQeo- riqhk ve-co.sse gd GCU#S 8. Notice the star Capella has the same spectral type as the Sun. What does it mean when two stars have the same spectral type? sazj comeosR+RYL The Sun's absolute magnitude is about +5. How many times brighter is Capella than the Sun (use Table 2)? How do the surface areas of Capella and the Sun compare? Umps How do the radii of the two stars compare? Explain your reasoning. fadiovs Page 57

The H-R Diagram Now let's work with Figure 2, the HR Diagram of the Brightest Stars. This diagram shows some of the brightest stars visible in the night sky. Use this diagram for questions 11 15. 11. How would you characterize the temperatures of the brightest stars in comparison to the Sun? b e O n A-Vun Sun. four St-MS on 2 A-von sun, 12. When you observe one of the brightest stars in the night sky, you are most likely looking at a star of what spectral types? 13. Why is Rigel so much brighter than the Sun? ooc son 14. Why is the luminosity of Betelgeuse so much higher than the Sun? %.z-ccww is biq0ps nok ia0k+Cx H'lßn Sun 15. Which star is larger, Rigel or Betelgeuse? Explain your reasoning. Is coou_r so be enernnvOVS in Page 59

Astronomy 1103 Laboratory Manual Now look at the Figure 3. This is an HR Diagram with only the nearest stars to Earth plotted. 16. What are the spectral types of the most common kind of stars near the Earth? IVI On average are these stars hotter or cooler than the Sun? COO lu 17. The star labeled Lalande 21185 has an apparent magnitude of 7.5. Would this star be visible to the unaided eye? voould +0 vnotducl is Is this star closer or farther than 10 parsecs? Explain your reasoning. is •less I D parsecs seccwr.-e 1.0 Page 60

Astronomy 1103 Laborato Manuaj 21. On the HR diagram draw an X at the position of a star smaller than Star 3 but with the same luminosity. +0 OQ S+CA( 3 22. Which one of these stars is a red giant? Star q 23. Of the five stars shown on the graph, which ones are most likely main-sequence stars? 24. Star 1 is about 4 times hotter than Star 5. How much more energy does it radiate from each square meter of its surface compared to Star 5? Show your work. lö t Loööoå 4 — qva CSQ 30831 q oqzsqvyoo/35h3qB31.2S 5Jø;• Page 62

The H-R Diagram ( uns n) Kusou!tunn epnuußen 01mosqv Page 63