Exam 2 Key

Exam 2 Key - \ PHY180 Exam II ,f/[f- é ,, m i . ” f i 7...

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Unformatted text preview: \ PHY180 Exam II ,f/[f- é ,, m i . ” f i 7 Useful equations: Brightness=1/r2. ‘ 57:. d = Km where K is 1 for parsec, 3.26 for light year, 206265 for AU Section 1 Please completely answer each of the following questions 1) Describe the life cycle of a star like our sun. Please start before the star is ‘born’ and include, at a minimum, the relative size, source of fuel (if any) for each stage, and what is left after the star dies. (10 pt) 2) Please describe the process we use to determine the age of a star cluster. Include, at a minimum, what assumptions we make, why it should work, and both how we tell both quite old and VERY young clusters. (10130 Section 2 Please refer to the attached sheet of Color/Magnitude diagrams for M45, 47 Tue, Hyades and M15 for the following questions. Order the 4 clusters from oldest to youngest. (2 pt) Oldest 1) Li l 0: <7 3 A4? F Youngest 4) Order the 4 clusters from nearest to furthest from us. (2pt) Nearest 1) >/ T9 a. %___éUL£;_______ 3) TU {" Furthest 4) Determine the age for each cluster. (2pt) W fl§3;”§§,fl§§ 47 Tue 1) f l; f3 / fir”? f.’ fl? Hyades 2) ' ; M45 3) M15 4) Spectral Color Lifetime _'l_‘Xpe B—V (years) 0 -0.4 < 1,000,000 B —0.2 M 30,000,000 A 02 400,000,000 F 0.5 4,000,000,000 G 0.7 10,000,000,000 K 1:0 60,000,000,000 M 1.6 > 100,000,000,000 M45 AU. 2 1 0 0. 0. O. O. 4 6 8 O 2 .1. 4| 4| 2 2 > AIL I 1 fl . 4. . 1 , ‘ . , Q , . a 2 o 1: 1 J o9 , B . 0 flag??? a? as: 6. am 0 .9 H W 4. 3 _, m 0 W , , ., 2. W O W ,, H . , W 7 o w , . . 4.521115%111111111, , am 2 a ................... O 4 6 8 0 2 4 6 _ 4.; 1 1.. 4.1 «Hwy 21 0.4 0.8 1.2 1.8 0.0 24.0 -0.4 47 Tue 0 , 1.6 1.4 1.2 0.8 0.6 3-2 1-2 4 o 84 08 ‘. . o 4 o M. “1‘ O 2., a a ‘. o 4 . . o _ Section 3 On the attached HR Diagram label the following: (1 pt each) Red Supergiants Red Giants Main Sequence stars White Dwarf Stars Luminosity Temperature Spectral Type Mass of the star Radius of the star Using a dotted line trace the path our sun will make during its life. i0 8 4QGOO _2&ooo 13900 &000 @000 aSOO :OOOR0 3500 ~40 Section 4 Choose the best answer to each question. (lpt each) 1. The spectral type and color of a star tells us primarily its a. mass b. luminosity c. composition temperature 6. radius 2. The way we can identify the existence of a certain chemical element in the spectrum of a star is a. the number of spectral lines it makes. the pattern of the lines it makes. V c. the color of the star's spectrum. d. the doppler shift of the spectrum. e. the parallax. 3. ,a star has a parallax of 0.09 are seconds, how far is it from earth in AU? 3.3,; 2,291,833 AU b. 11AU 0. 4,125,300 AU d. 74 AU e. 20 AU 4. If 51 Pegasi were located at 100 parsec, how bright would it appear to us on earth? (Compared to its brightness at 10 parsecs) a. 25 times brighter b.“ 1/16 times brighter c. 4 times brighter 1/100 times brighter e. 100 times brighter 5. Star A is 16 parsecs from earth, and star B is 4 parsecs. They appear the same brightness to us in the sky. Star A is 16 times as luminous as star B. b. Star A is 4 times as luminous as star B. c. Star A is 1/16 as luminous as star B. d. Star A is 1/ 4 as luminous as star B. e. Star A is 1/160 as luminous as star B. 6. Where on the H-R diagram are the smallest main sequence stars? a. upper left upper right 0. lower left {3?} lower right e. near the center 7. In star cluster A stars from spectral type A to M, while in cluster B, there are no stars hotter than spectral type F. ,7: A is older than B b. A and B are the same age B is older than A d. Not enough information to tell which is older e. A has not yet “turned on 8. The sun formed a. from gas and dust in a nebula fd. at the same time as the earth and other planets b. in a cluster of stars all of the above are true c. about 41/2 billion years ago 9. ,uring the main—sequence phase of its life, a star fuses: .5} hydrogen to helium in its core. b. silicon to iron in a shell. c. helium to carbon in its core. d. helium to carbon in a shell. f e. carbon to oxygen in its core. ,1. 10. What is the heaviest element that stars like the sun can form during their normal lives? 11. 12. same fuel d. a. Helium. Oxygen. 0. Silicon. d. Iron. 6. Gold. Which of these is the SINGLE MOST IMPORTANT indicator of how a star will evolve? a. Radius. b. Chemical composition. Mass. d. Surface temperature. e. Distance. What is the common feature between all main sequence stars? a. same mass b. same age same size e. same distance 13flMhen a star's parallax is measured, a small parallax means that the star is: a 14. 15. 16. l7. 18. 19. 20. “ relatively far away. b. relatively close by. c. not very bright. d. small in radius. 6. high temperature. Which do all stars within a cluster NOT have in common with each other? a. all are at the same distance I b. all are the same age c. all are the same composition all are the same mass e. all of the above properties are the same Very large stars form a core composed largely of during the Red Supergiant phase? a. Helium Oxygen 0. Silicon Iron e. Gold Light can escape from a black hole. True False ’ Stars can live for more than 10 billion years. True False All stars on the main sequence use carbon as a fuel. True alse White dwarf stars can be up to 10 times as big as the sun. True alse A star 1,000,000 time the radius of the sun can be on the main sequence. True 1 ...
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Exam 2 Key - \ PHY180 Exam II ,f/[f- é ,, m i . ” f i 7...

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