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NAME ____________________________ Lab Night ________________________ HR DIAGRAM REPORT FORM (Rev 6/12) Using the enclosed graph sheets and the background handout, complete the following plots. Graphs – 10 pts each Questions – 3 pts each A. Plot an H-R diagram for the brightest stars from table 10.1. B. Plot an H-R diagram for the closest stars from table 10.2. 1. Which type of star is most common on each diagram? Choices are: Main Sequence (V), Giants (combine all I,II,III,IV types), White Dwarfs. Do not count Sun. Go to the tables to count. A._________________ B._________________ 2. In Table 10.1, the brightest stars, how many stars are brighter than the sun? Brighter means lower magnitude (M) not higher. If double both must be considered. # brighter than the sun: ________ In Table 10.2, the closest stars, how many stars are brighter than the sun? Brighter means lower magnitude (M) not higher. If double both must be considered. # brighter than the sun: ________ 3. How many of the star systems in Table 10.1 (brightest) are also in Table 10.2 (closest)? Do not count the Sun. If a star is a double star, only count once. # = _____________ 4. How many of the stars in table 10.1 are hotter than the Sun (spectral classes O,B,A,F)? If double star both must be considered. # = __________ How many of the stars in table 10.2 are hotter than the Sun (spectral classes O,B,A,F)? If double star both must be considered. # = __________ 5. Based on answers to 1-4 above fill in the blanks using close, hot or large. The twenty brightest stars in the night sky are most likely to be bright because they are _________ or __________ not because they are ____________. SPECTROSCOPIC PARALLAX Given the information below about some stars, find the distances to each star using the technique of spectroscopic parallax. Use Voyager data panel to find the apparent magnitude (m) and absolute magnitude (M). Then calculate the distance in parsecs using the formula for D below Fig 2. Check your distance by comparing it with value given by Voyager data panel. It may not be exactly the same due to uncertainty in distance and brightness measurements but if not close you need to correct error or suffer additional penalty. 2 points each table entry. Name Spectral Class Nekkar G8 III Alkaid B3 V Delta Cephei F5 Ib Tarazed K3 II Kochab K4 III Apparent Magnitude (m) Absolute Magnitude, (M) Calculated Distance (pc) Voyager Distance (pc) STELLAR RADIUS Use the equation for L at the bottom of the page with Figure 2 to calculate the radius of these stars compared to the Sun. If you solve for ratio of star values to Sun values the 4 pi and sigma drop out. 2 points each Star L(star)/ L(Sun) T (star)/ T(Sun) Vega 50 1.8 Arcturus 110 0 .7 Antares 1300 0.5 Spica 500 4.0 Deneb 43,000 1.6 R(star)/ R(Sun)