2023-03-22 カリフォルニア大学バークレー校(UCB)
◆カリフォルニア大学バークレー校の天体化学者とコーネル大学の天文学者は、この彗星が太陽周りの双曲線的な軌道から外れた謎めいた逸脱を単純な物理的メカニズムで説明できると主張しています。これは多くの氷彗星に共通するものであり、太陽光によって温められるにつれて水素が放出されることです。Oumuamuaが他の太陽系内でよく研究された彗星と異なる点は、そのサイズでした。小さすぎて、水素ガスが氷から噴出する際に作られた微小な推力によって太陽周りでの重力偏向がわずかに変化しました。
＜関連情報＞
- https://news.berkeley.edu/2023/03/22/surprisingly-simple-explanation-for-alien-comet-oumuamuas-weird-orbit/
- https://www.nature.com/articles/s41586-022-05687-w
H2O氷の中で放射線分解により生成されたH2から1I/’Oumuamuaを加速させる Acceleration of 1I/‘Oumuamua from radiolytically produced H2 in H2O ice
Jennifer B. Bergner & Darryl Z. Seligman
Nature Published:22 March 2023
DOI:https://doi.org/10.1038/s41586-022-05687-w
Abstract
In 2017, 1I/‘Oumuamua was identified as the first known interstellar object in the Solar System1. Although typical cometary activity tracers were not detected2,3,4,5,6, ‘Oumuamua showed a notable non-gravitational acceleration7. So far, there has been no explanation that can reconcile these constraints8. Owing to energetic considerations, outgassing of hyper-volatile molecules is favoured over heavier volatiles such as H2O and CO2 (ref. 9). However, there are theoretical and/or observational inconsistencies10 with existing models invoking the sublimation of pure H2 (ref. 9), N2 (ref. 11) and CO (ref. 12). Non-outgassing explanations require fine-tuned formation mechanisms and/or unrealistic progenitor production rates7,13,14,15. Here we report that the acceleration of ‘Oumuamua is due to the release of entrapped molecular hydrogen that formed through energetic processing of an H2O-rich icy body. In this model, ‘Oumuamua began as an icy planetesimal that was irradiated at low temperatures by cosmic rays during its interstellar journey, and experienced warming during its passage through the Solar System. This explanation is supported by a large body of experimental work showing that H2 is efficiently and generically produced from H2O ice processing, and that the entrapped H2 is released over a broad range of temperatures during annealing of the amorphous water matrix16,17,18,19,20,21,22. We show that this mechanism can explain many of ‘Oumuamua’s peculiar properties without fine-tuning. This provides further support3 that ‘Oumuamua originated as a planetesimal relic broadly similar to Solar System comets.
