日本地球惑星科学連合2018年大会

講演情報

[JJ] Eveningポスター発表

セッション記号 P (宇宙惑星科学) » P-AE 天文学・太陽系外天体

[P-AE20] 系外惑星

2018年5月24日(木) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:生駒 大洋(東京大学 大学院理学系研究科 地球惑星科学専攻)、成田 憲保(東京大学)

[PAE20-P01] 惑星保有星の表面組成について:原始星への降着過程の影響

*國友 正信1Guillot Tristan2井田 茂3竹内 拓 (1.東京大学、2.コートダジュール天文台、3.東京工業大学)

キーワード:惑星形成、星表面組成、前主系列星

Recent observations have suggested a correlation between the existence of planet and the surface composition of the host star: The Sun, harboring many planetary objects, is depleted in refractory elements compared to most solar twins (Melendez et al. 2009) and in some binary systems the stellar surface compositions depend on the total mass of their planets (e.g., Ramirez et al. 2011). Since the stellar surface composition is one of the important quantities in exoplanetary sciences to characterize the planetary systems, the understanding of the observed correlations is crucial. In this study, we explore the possibility that planet formation processes affect the stellar surface compositions. The formation of planetary objects in protoplanetary disks implies that the composition of disk gas is not constant with time. The stellar surface composition must then differ from the primordial one. In order to determine the magnitude of this effect, a key ingredient is the stellar surface convective zone whose thickness determines the dilution of the “planet pollution” signature. First, we investigate the evolution of young stellar objects in the new framework of disk accretion. From stellar evolution calculations, we find that the evolution can significantly deviate from the classical picture. Using up-to-date stellar evolution models, we estimate the compositional changes due to planet formation. We find that the magnitude of the modification is sensitive to the entropy of accreting materials during the protostellar phase. Last, we apply our models to determine whether the composition anomaly between the Sun and solar twins may be explained by the retention of refractories during solar system formation. We find that this is possible, but only if the ice-to-rock ratio in the solar-system planets is less than 0.23.