研究者業績

長谷川 直

ハセガワ スナオ  (Sunao Hasegawa)

基本情報

所属
国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 大学共同利用実験調整グループ 主任研究開発員
学位
博士(理学)(東京大学)

ORCID ID
 https://orcid.org/0000-0001-6366-2608
J-GLOBAL ID
200901078920834652
researchmap会員ID
5000019324

研究キーワード

 2

学歴

 3

受賞

 2

論文

 275
  • Jooyeon Geem, Masateru Ishiguro, Hiroyuki Naito, Sunao Hasegawa, Jun Takahashi, Yoonsoo P. Bach, Sunho Jin, Seiko Takagi, Tatsuharu Ono, Daisuke Kuroda, Tomohiko Sekiguchi, Kiyoshi Kuramoto, Tomoki Nakamura, Makoto Watanabe
    Astronomy & Astrophysics 688 A195-A195 2024年8月22日  
    Context. Ch-type asteroids are distinctive among other dark asteroids in that they exhibit deep negative polarization branches (NPBs). Nevertheless, the physical and compositional properties that cause their polarimetric distinctiveness are less investigated. Aims. We aim to investigate the polarimetric uniqueness of Ch-type asteroids by making databases of various observational quantities (i.e., spectroscopic and photometric properties as well as polarimetric ones) of dark asteroids. Methods. We conducted an intensive polarimetric survey of 52 dark asteroids (including 31 Ch-type asteroids) in the RC band to increase the size of polarimetric samples. The observed data were compiled with previous polarimetric, spectroscopic, and photometric archival data to find their correlations. Results. We find remarkable correlations between these observed quantities, particularly the depth of NPBs and their spectroscopic features associated with the hydrated minerals. The amplitude of the opposition effect in photometric properties also shows correlations with polarimetric and spectral properties. However, these observed quantities do not show noticeable correlations with the geometric albedo, thermal inertia, and diameter of asteroids. Conclusions. Based on the observational evidence, we arrive at our conclusion that the submicrometer-sized structures (fibrous or flaky puff pastry-like structures in phyllosilicates) in the regolith particles could contribute to the distinctive NPBs of hydrated asteroids.
  • Hasegawa, Sunao, Marsset, Michaël, DeMeo, Francesca E., Hanuš, Josef, Binzel, Richard P., Bus, Schelte J., Burt, Brian, Polishook, David, Thomas, Cristina A., Geem, Jooyeon, Ishiguro, Masateru, Kuroda, Daisuke, Vernazza, Pierre
    The Astronomical Journal 2024年5月1日  
    Large terrestrial bodies in our solar system like the Earth, Mars, Mercury, and the Moon exhibit geologically complex surfaces with compositional heterogeneity. From past studies using large telescopes and spacecraft, it was shown that asteroids with diameters larger than 100 km also show surface heterogeneity at hemispheric scales, while on smaller objects, such features remain to be detected. Here, we investigate candidates for surface heterogeneity in a sample of 130 main-belt asteroids using multiepoch spectroscopic data from the MIT–Hawaii Near-Earth Object Spectroscopic Survey, which has been observing asteroids for about 20 yr using a self-consistent observation technique. Twelve conservative candidates with spectra more than 3σ apart from each other at 2.4 μm and 52 optimistic candidates for surface heterogeneity are detected. These candidates include eight objects already reported as being heterogeneous. Our study suggests that the size boundary between small homogeneous asteroids and larger heterogeneous objects, if it exists, is lower than 100 km. A-type asteroids have a higher proportion of heterogeneous candidates than other asteroids. This may be because olivine, which is the main surface constituent of these objects, reacts more efficiently to space weathering with respect to pyroxene, such that a similar range of surface ages will translate into a wider range of optical-to-near-infrared spectral slopes in the case of A-type bodies....
  • Aline Percot, Farah Mahieddine, Hajime Yano, Sunao Hasegawa, Makoto Tabata, Akihiko Yamagishi, Hajime Mita, Alejandro Paredes-Arriaga, Marie-Christine Maurel, Jean-François Lambert, Donia Baklouti, Emilie-Laure Zins
    Gels 2024年4月6日  
  • Tatsuhiro Michikami, Axel Hagermann, Akira Tsuchiyama, Yushi Otsuka, Michihiko Nakamura, Satoshi Okumura, Harumasa Kano, Junya Matsuno, Sunao Hasegawa
    Icarus 116068-116068 2024年4月  
  • Sato, Masahiko, Kurosawa, Kosuke, Hasegawa, Sunao, Takahashi, Futoshi
    Journal of Geophysical Research (Planets) 2024年3月  
    Knowledge of the shock remanent magnetization (SRM) property is crucial for interpreting the spatial change in a magnetic anomaly observed over an impact crater. This study conducted two series of impact-induced SRM acquisition experiments by varying the applied field intensity (0-400 μT) and impact conditions. Systematic remanence measurements of cube-shaped subsamples cut from shocked basalt containing single-domain titanomagnetite were conducted to investigate the effects of changes in pressure and temperature on the SRM acquisition. The peak pressure and temperature distributions in the shocked samples were estimated using shock-physics modeling. SRM intensity was proportional to the applied field intensity of up to 400 μT. SRM intensity data for peak pressure and temperature of up to 8.0 GPa and 530 K, respectively, clearly show that it increases with increasing pressure and decreases with increasing temperature. The SRM has unblocking temperature components up to a Curie temperature of 510 K, and it easily demagnetizes with alternating field demagnetization. The observed SRM properties can be explained by the pressure-induced microcoercivity reduction and temperature-induced modification of the blocking curve. Although the remanence acquisition efficiency of the SRM is significantly lower than that of the thermoremanent magnetization (TRM), the magnetic anomaly originating from the SRM distribution in a broader region may show a contribution comparable to that of the impact-induced TRM distribution in a narrow region....

MISC

 632
  • 黒澤, 耕介, 佐藤, 雅彦, 大野, 遼, 富岡, 尚敬, 新原, 隆史, 長谷川, 直, KUROSAWA, Kosuke, SATO, Masahiko, ONO, Haruka, TOMIOKA, Naotaka, NIIHARA, Takafumi, HASEGAWA, Sunao
    令和4 年度宇宙科学に関する室内実験シンポジウム講演集 = Proceedings of 2023 Symposium on Laboratory Experiment for Space Science 2023年3月  
    令和4年度宇宙科学に関する室内実験シンポジウム(2023年3月6日-7日. オンライン開催) 2023 Symposium on Laboratory Experiment for Space Science (March 6-7, 2023. Online Meeting) 資料番号:SA6000187030 レポート番号: 30
  • 佐藤, 雅彦, 黒澤, 耕介, 長谷川, 直, 高橋, 太, SATO, Masahiko, KUROSAWA, Kosuke, HASEGAWA, Sunao, TAKAHASHI, Futoshi
    令和4 年度宇宙科学に関する室内実験シンポジウム講演集 = Proceedings of 2023 Symposium on Laboratory Experiment for Space Science 2023年3月  
    令和4年度宇宙科学に関する室内実験シンポジウム(2023年3月6日-7日. オンライン開催) 2023 Symposium on Laboratory Experiment for Space Science (March 6-7, 2023. Online Meeting) 資料番号:SA6000187031 レポート番号: 31
  • 岩田翔也, 平井隆之, 中澤淳一郎, 増地大陸, 長谷川直, 新井和吉, 矢野創
    宇宙科学技術連合講演会講演集(CD-ROM) 67th 2023年  
  • 柿木玲亜, 荒川政彦, 保井みなみ, 長谷川直, 山本裕也
    日本惑星科学会秋季講演会予稿集(Web) 2023 2023年  
  • 豊嶋遥名, 荒川政彦, 保井みなみ, 笹井遥, 長谷川直
    日本惑星科学会秋季講演会予稿集(Web) 2023 2023年  

講演・口頭発表等

 132

共同研究・競争的資金等の研究課題

 16