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| 題名: | Acceleration of individual, decimetre-sized aggregates in the lower coma of comet 67P/Churyumov-Gerasimenko |
| 作者: | 葉永烜;Agarwal, Jessica;A'Hearn, M. F.;Vincent, J.-B.;Güttler, C.;Höfner, S.;Sierks, H.;Tubiana, C.;Barbieri, C.;Lamy, P. L.;Rodrigo, R.;Koschny, D.;Rickman, H.;Barucci, M. A.;Bertaux, J.-L.;Bertini, I.;Boudreault, S.;Cremonese, G.;Da Deppo, V.;Davidsson, B.;Debei, S.;De Cecco, M.;Deller, J.;Fornasier, S.;Fulle, M.;Gicquel, A.;Groussin, O.;Gutiérrez, P. J.;Hofmann, M.;Hviid, S. F.;Ip, W.-H.;Jorda, L.;Keller, H. U.;Knollenberg, J.;Kramm, J.-R.;Kührt, E.;Küppers, M.;Lara, L. M.;Lazzarin, M.;Lopez Moreno, J. J.;Marzari, F.;Naletto, G.;Oklay, N.;Shi, X.;Thomas, N. |
| 貢獻者: | 理學院天文研究所 |
| 關鍵詞: | Astrophysics;comets: general;comets: individual: 67P/Churyumov-Gerasimenko;Earth and Planetary Astrophysics;Sciences of the Universe;zodiacal dust |
| 日期: | 2016-01-01 |
| 上傳時間: | 2026-04-21 14:44:12 (UTC+8) |
| 出版者: | Oxford University Press;Oxford University Press (OUP) |
| 摘要: | 摘要： We present OSIRIS/NAC observations of decimetre-sized, likely ice-containing aggregates ejected from a confined region on the surface of comet 67P/Churyumov-Gerasimenko. The images were obtained in January 2016 when the comet was at 2 AU from the Sun out-bound from perihelion. We measure the acceleration of individual aggregates through a two-hour image series. Approximately 50% of the aggregates are accelerated away from the nucleus, and 50% towards it, and likewise towards either horizontal direction. The accelerations are up to one order of magnitude stronger than local gravity, and are most simply explained by the combined effect of gas drag accelerating all aggregates upwards, and the recoil force from asymmetric outgassing, either from rotating aggregates with randomly oriented spin axes and sufficient thermal inertia to shift the temperature maximum away from an aggregate's subsolar region, or from aggregates with variable ice content. At least 10% of the aggregates will escape the gravity field of the nucleus and feed the comet's debris trail, while others may fall back to the surface and contribute to the deposits covering parts of the northern hemisphere. The rocket force plays a crucial role in pushing these aggregates back towards the surface. Our observations show the future back fall material in the process of ejection, and provide the first direct measurement of the acceleration of aggregates in the innermost coma (<2km) of a comet, where gas drag is still significant.
出版者： Oxford University Press (OUP)
出版日期： 2016-11-01
出處： Monthly Notices of the Royal Astronomical Society, 2016-11, Vol.462 (Suppl 1), p.S78-88
資源來源： Alma/SFX Local Collection
版權： CC0 1.0 - Universal
識別號： ISSN: 0035-8711
識別號： ISSN: 1365-2966
識別號： ISSN: 1365-8711
識別號： EISSN: 1365-2966
識別號： DOI: 10.1093/mnras/stw2179 |
| 顯示於類別: | [天文研究所] 期刊論文
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