天文與重力中心專題演講2/25


活動舉辦:

國立臺灣師範大學 理學院


活動地點:B101
發起學校:臺師大
開始日期:2021-02-25 16:27
結束日期:2021-02-25 16:31
活動類別:學術活動

報名方式: 免費入場
活動網址:
參加對象: 教職員,學生,校友,其他,
聯絡人: 李怡萱
連絡電話: 6035
電子郵件: 410008032@gms.ndhu.edu.tw

Title:The first interstellar object, 1I/'Oumuamua

Abstract:

The arrival of ISOs -- and specifically the appearance of 1I/'Oumuamua -- points to a significant number density of free-floating bodies in the Solar neighborhood. We study the details of 'Oumuamua's pre-encounter galactic orbit and find that it encountered our Sun at very nearly its maximum vertical and radial excursion relative to the galactic plane. 'Oumuamua's kinematics, moreover, strongly resemble those of nearby Young Associations. To obtain an order-of-magnitude a-priori age estimate, we compared 'Oumuamua's orbit to the orbits of 13,066 F-type stars drawn from the Gaia DR2, and with a simple diffusion model, we find tau_`O ~35 Myr. We then compare 'Oumuamua's orbit with the trajectories of nearby moving groups, confirming that its motion is consistent with its membership in the Carina and Columba associations, whose ages are 45 Myr. We conducted Monte Carlo simulations that trace the orbits of test particles ejected from the stars in the Carina and Columba associations. We find that to achieve the inferred Pan-STARRS number density of 0.2 ISOs per au^3, the required ejection mass is ~ 100 M_{Jup} per known star within the associations. The Pan-STARRS observation is thus in significant tension with scenarios that posit 'Oumuamua's formation and ejection from a protostellar disk.


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