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平田 直之 

 理学研究科・惑星学専攻・惑星宇宙物理学教育研究分野 助教


研究と教育

 固体天体・衛星・小惑星の表面・表層について観測・理論を用いて幅広く研究をしています。観測手法として、太陽系探査によって得られた固体天体のリモートセンシング画像データ解析を行っています。特に木星・土星の氷衛星に詳しいですが小惑星や火星・月もやっています。データ解析の科学的意義を最大化して研究として成立させるためには、理論的な視点…背景にある物理的あるいは化学的な諸現象について深く理解しそれらと連携させることが欠かせません。これらの取り組みを通じて、各天体の進化を明らかにすることで、地球の独自性や普遍性の一端を解明したいと考えています。 授業では数値積分・常微分・偏微分方程式の数値解法を教える実習を担当しています。数値計算の実習は、学生間の力量差がたいへん大きく、初学者と熟練者を同時に相手にする授業に日々苦心しており、毎年、試行錯誤しております。



主な研究テーマ 

  • 惑星地質学・惑星物理学
  • 惑星・衛星・小天体の起源と進化

  • 査読付き英語原著論文一覧 

    • 1. R. Ikeya and N. Hirata (2021), Ejecta emplacement as the possible origin of Ryugu's equatorial ridge, Icarus 367, 114590
    • 2. N. Hirata and R. Ikeya (2021), Ejecta distribution from impact craters on Ryugu: Possible origin of the bluer units, Icarus 364, 114474
    • 3. N. Hirata et al., (2021), Rotational effect as the possible cause of the east-west asymmetric crater rims on Ryugu observed by LIDAR data, Icarus 354,114073.
    • 4. N. Hirata, Ryu Suetsugu, Keiji Ohtsuki, (2020), A global system of furrows on Ganymede indicative of their creation in a single impact event, Icarus 352, 113941.
    • 5. N. Hirata et al. (2020), The spatial ditribution of craters on Ryugu, Icarus 338, 113527, pp. 1-6.
    • 6. R. Noguchi, N. Hirata, et al. (2021), Crater depth-to-diameter ratios on asteroid 162173 Ryugu, Icarus 354, 114016.
    • 7. K. Ohtsuki, H. Kawamura, Naoyuki Hirata, H. Daisaka, H. Kimura (2020), Size of the smallest particles in Saturn's rings, Icarus 344, 113346, pp. 1-11.
    • 8. S. Watanabe, M. Hirabayashi, Naru Hirata, Naoyuki Hirata et al. (著者数89人) (2019), Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu - A spinning top–shaped rubble pile, Science 364, Issue 6437, pp. 268-272.
    • 9. L. Xu, Naoyuki Hirata, H. Miyamoto (2019), Spatial distribution of ray craters on Callisto: Implications for ray retention and impactor sources on Jovian satellites, Journal of Geophysical Research Planets 124, pp. 1717-1727.
    • 10. L. Xu, N. Hirata, and H. Miyamoto (2017), Ray craters on Ganymede: Implications for cratering apex-antapex asymmetry and surface modification processes, Icarus, 295, pp. 140-148. 11. Hirata, N. (2017), Spatial distribution of impact craters on Deimos, Icarus 288(15), pp. 69-77.
    • 12. Hirata, N. (2016),Timing of the faulting on the Wispy Terrain of Dione based on stratigraphic relationships with impact craters, Journal of Geophysical Research Planets 121(11), pp. 2325-2335
    • 13. Hirata, N. (2016), Differential impact cratering of Saturn’s satellites by heliocentric impactors, Journal of Geophysical Research Planets 121(2), pp. 111-117.
    • 14. Hirata, N. and Miyamoto, H. (2016), Rayed craters on Dione: Implication for the dominant surface alteration process, Icarus 274, pp. 116–121.
    • 15. Hirata, N., Miyamoto, H., and A. P. Showman (2014), Particle deposition on the saturnian satellites from ephemeral cryovolcanism on Enceladus, Geophysical Research Letters 41(12), pp. 4135–4141.
    • 16. Hirata, N. and H. Miyamoto (2012), Dust levitation as a major resurfacing process on the surface of a saturnian icy satellite, Atlas, Icarus 220(1), pp. 106-11.
    • 17. S. Kikuchi, N. Ogawa, O. Mori, T. Saiki, Y. Takei, F. Terui, G. Ono, Y. Mimasu, K. Yoshikawa, S.V. Wal, H. Takeuchi, H. Ikeda, A. Fujii, Y. Takao, T. Kusumoto, N. Hirata, Naoyuki Hirata, et al. (2021), Ballistic deployment of the Hayabusa2 artificial landmarks in the microgravity environment of Ryugu, Icarus 358, 114220.
    • 18. E. Tatsumi, C. Sugimoto, L. Riu , S. Sugita, T. Nakamura, T. Hiroi, T. Morota, M. Popescu, T. Michikami, K. Kitazato, M. Matsuoka, S. Kameda, R. Honda, M. Yamada, N. Sakatani, T. Kouyama, Y. Yokota , C. Honda , H. Suzuki , Y. Cho , K. Ogawa, M. Hayakawa, H. Sawada, K. Yoshioka, C. Pilorget, M. Ishida, D. Domingue, Naoyuki Hirata, et al. (著者数74人) (2020), Collisional history of Ryugu’s parent body from bright surface boulders, Nature Astronomy in press.
    • 19. T. Morota, S. Sugita, Y. Cho, M. Kanamaru, E. Tatsumi, N. Sakatani, R. Honda, N. Hirata, H. Kikuchi, M. Yamada, Y. Yokota, S. Kameda, M. Matsuoka, H. Sawada, C. Honda, T. Kouyama, K. Ogawa, H. Suzuki, K. Yoshioka, M. Hayakawa, N. Hirata, et al. (著者数95人) (2020), Sample collection from asteroid (162173) Ryugu by Hayabusa2: Implications for surface evolution, Science 368, Issue 6491, pp. 654-659.
    • 20. Matsumoto, K., Noda, H., Ishihara, Y., Senshu, H., Yamamoto, K., Hirata, N., Hirata, N., Namiki, N., Otsubo, T., Higuchi, A., Watanabe, S.-I., Ikeda, H., Mizuno, T., Yamada, R., Araki, H., Abe, S., Yoshida, F., Sasaki, S., Oshigami, S., Tsuruta, S., Asari, K., Shizugami, M., Yamamoto, Y., Ogawa, N., Kikuchi, S., Saiki, T., Tsuda, Y., Yoshikawa, M., Tanaka, S., Terui, F., Nakazawa, S., Yamaguchi, T., Takei, Y., Takeuchi, H., Okada, T., Yamada, M., Shimaki, Y., Shirai, K., Ogawa, K., Iijima, Y.-I. (2020), Improving Hayabusa2 trajectory by combining LIDAR data and a shape model, Icarus 338, 113574, pp. 1-8.
    • 21. Okada, T., Fukuhara, T., Tanaka, S., Taguchi, M., Arai, T., Senshu, H., Sakatani, N., Shimaki, Y., Demura, H., Ogawa, Y., Suko, K., Sekiguchi, T., Kouyama, T., Takita, J., Matsunaga, T., Imamura, T., Wada, T., Hasegawa, S., Helbert, J., Müller, T.G., Hagermann, A., Biele, J., Grott, M., Hamm, M., Delbo, M., Hirata, N., Hirata, N.,et al. (著者数80人) (2020), Highly porous nature of a primitive asteroid revealed by thermal imaging, Nature 579, Issue 7800, pp. 518-522.
    • 22. Arakawa, M., Saiki, T., Wada, K., Ogawa, K., Kadono, T., Shirai, K., Sawada, H., Ishibashi, K., Honda, R., Sakatani, N., Iijima, Y., Okamoto, C., Yano, H., Takagi, Y., Hayakawa, M., Michel, P., Jutzi, M., Shimaki, Y., Kimura, S., Mimasu, Y., Toda, T., Imamura, H., Nakazawa, S., Hayakawa, H., Sugita, S., Morota, T., Kameda, S., Tatsumi, E., Cho, Y., Yoshioka, K., Yokota, Y., Matsuoka, M., Yamada, M., Kouyama, T., Honda, C., Tsuda, Y., Watanabe, S., Yoshikawa, M., Tanaka, S., Terui, F., Kikuchi, S., Yamaguchi, T., Ogawa, N., Ono, G., Yoshikawa, K., Takahashi, T., Takei, Y., Fujii, A., Takeuchi, H., Yamamoto, Y., Okada, T., Hirose, C., Hosoda, S., Mori, O., Shimada, T., Soldini, S., Tsukizaki, R., Iwata, T., Ozaki, M., Abe, M., Namiki, N., Kitazato, K., Tachibana, S., Ikeda, H., Hirata, N., Hirata, N., Noguchi, R., Miura, A. (2020), An artificial impact on the asteroid (162173) Ryugu formed a crater in the gravity-dominated regime, Science 368, Issue 6486, pp. 67-71.
    • 23. Barucci, M.A, Hasselmann, P.H., Fulchignoni, M, Honda, R., Yokota, Y., Sugita, S., Kitazato, K., Deshapriya, J.D.P., Perna, D., Tatsumi, E., Domingue, D., Morota, T., Kameda, S., Iwata, T., Abe, M., Ohtake, M., Matsuura, S., Matsuoka, M., Hiroi, T., Nakamura, T., Kouyama, T., Suzuki, H., Yamada, M., Sakatani, N., Honda, C., Ogawa, K., Hayakawa, M., Yoshioka, K., Cho, Y., Sawada, H., Takir, D., Vilas, F., Naru Hirata, Naoyuki Hirata, Tanaka, S., Yamamoto, Y., Yoshikawa, M., Watanabe, S., Tsuda, Y. (2019), Multivariable statistical analysis of spectrophotometry and spectra of (162173) Ryugu as observed by JAXA Hayabusa2 mission, Astronomy and Astrophysics 629, A13, pp. 1-10.
    • 24. T. Michikami, C. Honda, H. Miyamoto, M. Hirabayashi, A. Hagermann, T. Irie, K. Nomura, C. M. Ernst, M. Kawamura, K. Sugimoto, E. Tatsumi, T. Morota, N. Hirata, T. Noguchi, Y. Cho, S. Kameda, T. Kouyama, Y. Yokota, R. Noguchi, M. Hayakawa, Naoyuki Hirata et al.(著者数36人) (2019), Boulder size and shape distributions on asteroid Ryugu, Icarus 331, pp. 179-191
    • 25. K. Kitazato, R. E. Milliken, T. Iwata, M. Abe, M. Ohtake, S. Matsuura, T. Arai, Y. Nakauchi, T. Nakamura, M. Matsuoka, H. Senshu, Naru Hirata, T. Hiroi, C. Pilorget, R. Brunetto, F. Poulet, L. Riu, J.-P. Bibring, D. Takir, D. L. Domingue, F. Vilas, M. A. Barucci, D. Perna, E. Palomba, A. Galiano, K. Tsumura, T. Osawa, M. Komatsu, A. Nakato, T. Arai, N. Takato, T. Matsunaga, Y. Takagi, K. Matsumoto, T. Kouyama, Y. Yokota, E. Tatsumi, N. Sakatani, Y. Yamamoto, T. Okada, S. Sugita, R. Honda, T. Morota, S. Kameda, H. Sawada, C. Honda, M. Yamada, H. Suzuki, K. Yoshioka, M. Hayakawa, K. Ogawa, Y. Cho, K. Shirai, Y. Shimaki, N. Hirata et al. (著者数66人) (2019), The surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy, Science, 364, Issue 6437, pp. 272-275.
    • 26. M. Hirabayashi, E. Tatsumi, H. Miyamoto, G. Komatsu, S. Sugita, S. Watanabe, D. J. Scheeres, O. S. Barnouin, P. Michel, C. Honda, T. Michikami, Y. Cho, T. Morota, N. Hirata, Naoyuki Hirata et al. (著者数29人) (2019), The western bulge of 162173 Ryugu formed as a result of a recent deformation process, Astrophysical Journal Letters 874, Number 1, pp. 1-6.
    • 27. O. S. Barnouin, M. G. Daly, E. E. Palmer, R. W. Gaskell, J. R. Weirich, C. L. Johnson, M. M. Al Asad, J. H. Roberts, M. E. Perry, H. C. M. Susorney, R. T. Daly, E. B. Bierhaus, J. A. Seabrook, R. C. Espiritu, A. H. Nair, L. Nguyen, G. A. Neumann, C. M. Ernst, W. V. Boynton, M. C. Nolan, C. D. Adam, M. C. Moreau, B. Rizk, C. Y. Drouet D’Aubigny, E. R. Jawin, K. J. Walsh, P. Michel, S. R. Schwartz, R.-L. Ballouz, E. M. Mazarico, D. J. Scheeres, J. W. McMahon, W. F. Bottke, S. Sugita, Naru Hirata, Naoyuki Hirata (2019), Shape of (101955) Bennu indicative of a rubble pile with internal stiffness, Nature Geoscience 12, pp. 247–252.
    • 28. S. Sugita, R. Honda, T. Morota, S. Kameda, H. Sawada, E. Tatsumi, M. Yamada, C. Honda, Y. Yokota, T. Kouyama, N. Sakatani, K. Ogawa, H. Suzuki, T. Okada, N. Namiki, S. Tanaka, Y. Iijima, K. Yoshioka, M. Hayakawa, Y. Cho, M. Matsuoka, Naru Hirata, Naoyuki Hirata et al. (著者数120人) (2019), The geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes, Science 364, Issue 6437, eaaw0422, pp. 1-11.

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                                                    更新日 2022年4月


           

神戸大学 理学研究科 惑星学専攻

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