USAAAO — 2024 First Round
Question 6
Newly discovered planets DDP and CJ are found to orbit a nearby star, as shown in the figure below. Planet CJ has a circular orbit with a radius of 2d, while planet DDP moves in an elliptical orbit with an aphelion of d and a perihelion of 5d. Their orbits intersect at location B in the figure. Additionally, through external analysis, planet DDP is found to be three times more massive than planet CJ. From the perspective of the star, what is the ratio of the angular momentum of planet DDP when it passes through point B to the angular momentum of planet CJ when it passes through point B? You may assume that the masses of both planets are significantly smaller than the mass of the star they orbit.
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Source
USAAAO 2024 First Round, Question 6. Question text, choices, and answer were transcribed from the official USAAAO exam and solutions PDFs. Official orbit diagram omitted; consult the cited exam page.