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Motion of Extrasolar Planets 115 Center of Mass Center of Mass Star Extrasolar Planet Extrasolar Planet . Star . Fig 2. Extrasolar Planet and Star As Seen Edge-On Or From The Side Note that the extrasolar planet is moving toward you. (not to scale) Fig 1. Extrasolar Planet and Star As Seen From Above (not to scale) 1) Figure 1 and Figure 2 show the orbits of the same extrasolar planet and star from two different points of view. As an extrasolar planet orbits around a star, the gravitational attraction between the two objects causes the central star to make a small orbit around the system’s center of mass. Which object travels in the largest orbit? (circle one)? extrasolar planet the star they have the same sized orbit you can’t determine which has the larger orbit 2) Which object takes a greater amount of time to complete one orbit (circle one)? extrasolar planet takes longer central star takes longer they both take the same amount of time you can’t determine which takes longer Explain your reasoning. 3) At the instant shown in Figure 1, which direction is the extrasolar planet moving (circle one)? toward the bottom of the page toward the top of the page toward the central star 4) At the instant shown in Figure 1, which direction is the central star moving (circle one)? toward the bottom of the page PEARSON PRENTICE HALL toward the top of the page toward the extrasolar planet LECTURE-TUTORIALS FOR INTRODUCTORY ASTRONOMY SECOND EDITION, 2007 Motion of Extrasolar Planets 116 5) In general how does the direction the extrasolar planet is moving compare with the direction the central star is moving? 6) Figure 2 shows the extrasolar planet and star from the side or as seen edge-on. At the instant shown, which direction is the planet moving (circle one)? coming out of the page directly toward you moving into the page directly away from you toward the central star 7) Two students are having a discussion about the relationship between the movement of the star and planet and Doppler shift of the light coming from the star. Student 1: Since Figure 2 states that the extrasolar planet is moving out of the page, directly toward us, then the light from the star we observe will be blueshifted. Student 2: I disagree, the light from the star will be redshifted because the star is moving the opposite direction the planet is moving. Do you agree or disagree with either or both of the students? Why? 8) Suppose instead that the extrasolar planet (shown in Figures 1 and 2) became much more massive, but continued orbiting at the same distance. How would your observations from Earth be different (circle one)? the star’s light would be shifted even more the star’s light would be shifted less than before no change in the light would be observed Explain your reasoning. 9) Suppose instead that the extrasolar planet (shown in Figures 1 and 2) moved farther away from the star, but continued to have the same mass. How would your observations from Earth be different (circle one)? the star’s light would be shifted even more the star’s light would be shifted less than before no change in the light would be observed Explain your reasoning. LECTURE-TUTORIALS FOR INTRODUCTORY ASTRONOMY SECOND EDITION, 2007 PEARSON PRENTICE HALL Motion of Extrasolar Planets 117 10) Under what condition would you NOT observe a star’s light to ever undergo Doppler shift even when there is an extrasolar planet orbiting the star? Explain your reasoning, and include a drawing to illustrate your answer in the space below. 1 2 3 4 5 Velocity (m/s) -20 3 20 2 4 5 8 10 Time (years) 2 20 -20 Time (years) -20 Velocity (m/s) 1 20 Velocity (m/s) Velocity (m/s) 11) Consider the four graphs shown below which show the radial velocity of four stars. 5 4 20 -20 10 15 20 25 Time (years) 3 9 12 15 6 Time (years) a. From which star would you obseve the greatest Doppler Shift? Explain your reasoning. b. Which planet has the longest orbital period? Explain your reasoning. PEARSON PRENTICE HALL LECTURE-TUTORIALS FOR INTRODUCTORY ASTRONOMY SECOND EDITION, 2007 118 Motion of Extrasolar Planets 12) Given the location marked with the dot on the star’s radial velocity curve, at what location (1-4) would you expect the planet to be located at this time? Explain your reasoning. 1 Radial Velocity 20 m/s Orbit of star Earth 10 m/s 4 2 Time -10 m/s - 20 m/s Orbit of planet LECTURE-TUTORIALS FOR INTRODUCTORY ASTRONOMY SECOND EDITION, 2007 3 PEARSON PRENTICE HALL