Research activity information

• Nov. 2013 日本学術振興会, 科研費・審査委員表彰, 有意義な審査意見を付していただいた専門委員

  OHTSUKI KEIJI

  Publisher

• Color and Size Distributions of Small Jupiter Trojans

  Fumi Yoshida, Tsuyoshi Terai, Keiji Ohtsuki

  Abstract We conducted a two-band imaging survey observation using the Subaru Telescope and its wide-field camera, Suprime-Cam, to study the visible colors and size distribution of Jupiter’s Trojan asteroids. The survey covered an area around Jupiter’s L4 Lagrange point totaling 9.2 square degrees. We detected 120 Trojan asteroids in this survey. From these Trojan asteroids, we extracted 44 unbiased samples with absolute magnitudes in the band ranging from 12.9 to 16.9 mag (corresponding to diameter ranges of approximately ∼3–16 km assuming an albedo of 0.05) and analyzed their color and size distributions. Large Jupiter Trojan asteroids are known to be classified into two color groups, “red” and “less red.” We found that such bimodality in the color distribution is absent for small Jupiter Trojan asteroids, which is consistent with previous studies. Previous studies have also shown that these two groups have different slopes in the magnitude distributions from each other, which was explained by conversion of red objects to less-red fragments through catastrophic disruptions. In contrast, we found that the size frequency distributions of our two sample groups divided by the color of  = 0.7 (in AB magnitude) are quite similar. Our results can provide new insights into collisional evolution of color and size distribution of small Jupiter Trojans.

  American Astronomical Society, Apr. 2026, The Astronomical Journal, 171(4) (4), 240 - 240, English

  [Refereed]

  Scientific journal


• Global N-body simulation of propeller formation in Saturn's rings

  Ryo Tamon, Keiji Ohtsuki

  Mar. 2026, LPI Contributions, English

  International conference proceedings


• Influence of target's gravity on ejecta dynamics and change in asteroid velocity

  Takato Nishio, Keiji Ohtsuki, Keisuke Sugiura

  Mar. 2026, LPI Contributions


• Rings around giant planets and smaller bodies

  Keiji Ohtsuki

  Jan. 2026, Encyclopedia of Astrophysics, 1, 66 - 84, English

  [Refereed][Invited]

  In book


• FOSSIL. IV. The Significance-convergence Test—An Algorithm for Selecting Reliable Rotation Periods of Small Solar System Bodies

  Chan-Kao Chang, Ying-Tung Chen, Matthew J. Lehner, Shiang-Yu Wang, Mike Alexandersen, Young-Jun Choi, Wesley C. Fraser, A. Paula Granados Contreras, Takashi Ito, Youngmin JeongAhn, Jianghui Ji, J. J. Kavelaars, Myung-Jin Kim, Jian Li, Zhong-Yi Lin, Patryk Sofia Lykawka, Hong-Kyu Moon, Surhud More, Marco Muñoz-Gutiérrez, Keiji Ohtsuki, Rosemary E. Pike, Tsuyoshi Terai, Seitaro Urakawa, Fumi Yoshida, Hui Zhang, Haibin Zhao, Ji-Lin Zhou

  Abstract Manual review to select a reliable rotation period of small solar system bodies (SSSBs) is a very time-consuming process. With the growing volume of lightcurve data collected by wide-field, high-cadence surveys, such manual inspection has become impractical and unsustainable. In response to this challenge, we present a new algorithm, called the significance-convergence test, which provides a quantitative way to select reliable rotation periods of SSSBs obtained from these wide-field, high-cadence surveys. This algorithm was developed based on two simulations, each containing 162,000 synthetic lightcurves generated according to the observational conditions and data properties of the surveys from the phase I of the Formation of the Outer Solar System: an Icy Legacy (FOSSIL I) and Pan-STARRS 1 (PS1). Using two parameters extracted from period analysis, the successful recoveries of the input rotation periods from the synthetic lightcurves can be distinguished from unsuccessful recoveries and noisy lightcurves. The first parameter, 1/ S , indicates the significance of the best-fit spin rate, while the second parameter, C , represents the condition of convergence of the best-fit lightcurve. This algorithm can also be used as a mapping to the conventional quality code of manual review, U , defined by Warner et al. The significance-convergence test thus provides a practical alternative to manual review, which is a time-consuming and biased process.

  IOP Publishing, Oct. 2025, Publications of the Astronomical Society of the Pacific, 137(10) (10), 104509 - 104509, English

  [Refereed]

  Scientific journal


• Discovery and dynamics of a Sedna-like object with a perihelion of 66 au

  Ying-Tung Chen, Patryk Sofia Lykawka, Yukun Huang, JJ Kavelaars, Wesley C. Fraser, Michele T. Bannister, Shiang-Yu Wang, Chan-Kao Chang, Matthew J. Lehner, Fumi Yoshida, Brett Gladman, Mike Alexandersen, Edward Ashton, Young-Jun Choi, A. Paula Granados Contreras, Takashi Ito, Youngmin JeongAhn, Jianghui Ji, Myung-Jin Kim, Samantha M. Lawler, Jian Li, Zhong-Yi Lin, Hong-Kyu Moon, Surhud More, Marco Muñoz-Gutiérrez, Keiji Ohtsuki, Lowell Peltier, Rosemary E. Pike, Tsuyoshi Terai, Seitaro Urakawa, Hui Zhang, Haibin Zhao, Ji-Lin Zhou

  Springer Science and Business Media LLC, Sep. 2025, Nature Astronomy, 9, 1309 - 1316, English

  [Refereed]

  Scientific journal


• Numerical Simulation for Velocity Changes After a Disruptive Impact Between Asteroids

  Nishio, T., Ohtsuki, K., Sugiura, K.

  Apr. 2025, Apophis T-4 Years, LPI Contributions, 3083, 2046, English

  International conference proceedings


• Accretion of gas and dust onto circumplanetary disks around giant planets

  Natsuho Maeda, Keiji Ohtsuki

  Dec. 2024, Planetary People, 33(4) (4), 430 - 435, Japanese

  [Refereed]


• Change in Asteroid Velocity Due to Disruptive Impact

  Takato Nishio, Keiji Ohtsuki, Keisuke Sugiura

  Sep. 2024, Planetary People, 33(3) (3), 254 - 261, Japanese

  [Refereed]


• Delivery of Dust Particles from Protoplanetary Disks onto Circumplanetary Disks of Giant Planets

  Natsuho Maeda, Keiji Ohtsuki, Ryo Suetsugu, Yuhito Shibaike, Takayuki Tanigawa, Masahiro N. Machida

  Abstract The principal regular satellites of gas giants are thought to be formed by the accumulation of solid materials in circumplanetary disks (CPDs). While there has been significant progress in the study of satellite formation in CPDs, details of the supply of satellite building blocks to CPDs remain unclear. We perform the orbital integration of solid particles in the protoplanetary disk (PPD) approaching a planet, considering the gas drag force by using the results of three-dimensional hydrodynamical simulations of a local region around the planet. We investigate the planetary mass dependence of the capture positions and the capture rates of dust particles accreting onto the CPD. We also examine the degree of dust retention in the accreting gas onto the CPD, which is important for determining the ratio of the dust-to-gas inflow rates, a key parameter in satellite formation. We find that the degree of dust retention increases with increasing planetary mass for a given dust scale height in the PPD. In the case of a small planet (M _p = 0.2M _Jup), most particles with insufficient initial altitudes in the PPD are isolated from the gas in the accreting region. On the other hand, in the case of a massive planet (M _p = 1M _Jup), dust particles can be coupled to the vertically accreting gas, even when the dust scale height is about 10%–30% of the gas scale height. The results of this study can be used for models of dust delivery and satellite formation in the CPDs of gas giants of various masses, including exoplanets.

  American Astronomical Society, Jun. 2024, The Astrophysical Journal, 968(2) (2), 62 - 62, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• FOSSIL. III. Lightcurves of 371 Trans-Neptunian Objects

  Edward Ashton, Chan-Kao Chang, Ying-Tung Chen, Matthew J. Lehner, Shiang-Yu Wang, Mike Alexandersen, Young-Jun Choi, Wesley C. Fraser, A. Paula Granados Contreras, Takashi Ito, Youngmin JeongAhn, Jianghui Ji, JJ Kavelaars, Myung-Jin Kim, Samantha M. Lawler, Jian Li, Zhong-Yi Lin, Patryk Sofia Lykawka, Hong-Kyu Moon, Surhud More, Marco A. Muñoz-Gutiérrez, Keiji Ohtsuki, Rosemary E. Pike, Tsuyoshi Terai, Seitaro Urakawa, Fumi Yoshida, Hui Zhang, Haibin Zhao, Ji-Lin Zhou

  Abstract From the first phase of the high-cadence Formation of the Outer Solar System: an Icy Legacy (FOSSIL) survey, we analyzed lightcurves, ranging from one to four nights in length, of 371 trans-Neptunian objects (TNOs) for periodicity. We found 29 TNOs with periodic lightcurves, one of which is a good candidate for a close/contact binary. Another of the periodic FOSSIL TNOs could potentially have the fastest of all known TNO spin rates, with a period of 1.3 hr. We do not have total confidence in the period and thus plan to obtain a more detailed lightcurve for confirmation. The periodic TNOs have an average rotation period of 11.2 hr, close to the value obtained by Alexandersen et al., which had similar cadence, but different from other surveys. In regards to contention in the literature about whether smaller TNOs are more irregular in shape and thus have larger lightcurve amplitudes, we found that there is a weak correlation between absolute magnitude and lightcurve amplitude in a subset of 194 FOSSIL TNOs, even when using the more appropriate brightest (minimum) absolute magnitude instead of the time-averaged value.

  American Astronomical Society, Jul. 2023, The Astrophysical Journal Supplement Series, 267(2) (2), 33 - 33, English

  [Refereed]

  Scientific journal


• Delivery of Gas onto the Circumplanetary Disk of Giant Planets: Planetary-mass Dependence of the Source Region of Accreting Gas and Mass Accretion Rate

  Natsuho Maeda, Keiji Ohtsuki, Takayuki Tanigawa, Masahiro N. Machida, Ryo Suetsugu

  Abstract Gas accretion onto the circumplanetary disks and the source region of accreting gas are important to reveal dust accretion that leads to satellite formation around giant planets. We performed local three-dimensional high-resolution hydrodynamic simulations of an isothermal and inviscid gas flow around a planet to investigate the planetary-mass dependence of the gas accretion bandwidth and gas accretion rate onto circumplanetary disks. We examined cases with various planetary masses corresponding to M_p = 0.05–1M_Jup at 5.2 au, where M_Jup is the current Jovian mass. We found that the radial width of the gas accretion band is proportional to ${M}_{ { \rm{p } } }^{1/6}$ for the low-mass regime with M_p ≲ 0.2M_Jup while it is proportional to M_p for the high-mass regime with M_p ≳ 0.2M_Jup. We found that the ratio of the mass accretion rate onto the circumplanetary disk to that into the Hill sphere is about 0.4 regardless of the planetary mass for the cases we examined. Combining our results with the gap model obtained from global hydrodynamic simulations, we derive a semi-analytical formula of mass accretion rate onto circumplanetary disks. We found that the mass dependence of our three-dimensional accretion rates is the same as the previously obtained two-dimensional case, although the qualitative behavior of accretion flow onto the circumplanetary disk is quite different between the two cases.

  American Astronomical Society, Aug. 2022, The Astrophysical Journal, 935(1) (1), 56 - 56

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Size Distribution of Small Jupiter Trojans in the L₅ Swarm

  Kotomi Uehata, Tsuyoshi Terai, Keiji Ohtsuki, Fumi Yoshida

  Abstract We present an analysis of survey observations of the trailing L₅ Jupiter Trojan swarm using the wide-field Hyper Suprime-Cam CCD camera on the 8.2 m Subaru Telescope. We detected 189 L₅ Trojans from our survey that covered about 15 deg² of sky with a detection limit of m_r = 24.1 mag, and selected an unbiased sample consisting of 87 objects with absolute magnitude 14 ≲ H_r ≤ 17 corresponding to diameter 2 km ≲ D ≲ 10 km for analysis of size distribution. We fit their differential magnitude distribution to a single-slope power law with an index α = 0.37 ± 0.01, which corresponds to a cumulative size distribution with an index of b = 1.85 ± 0.05. Combining our results with data for known asteroids, we obtained the size distribution of L₅ Jupiter Trojans over the entire size range for 9 ≲ H_V ≤ 17, and found that the size distributions of the L₄ and L₅ swarms agree well with each other for a wide range of sizes. This is consistent with the scenario that asteroids in the two swarms originated from the same primordial population. Based on the above results, the ratio of the total number of asteroids with D ≥ 2 km in the two swarms is estimated to be N_L4/N_L5 = 1.40 ± 0.15, and the total number of L₅ Jupiter Trojans with D ≥ 1 km is estimated to be 1.1 × 10⁵ by extrapolating the obtained distribution.

  Corresponding, American Astronomical Society, May 2022, The Astronomical Journal, 163(5) (5), 213 - 213, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Dust release from cold ring particles as a mechanism of spoke formation in Saturn's rings

  Naoyuki Hirata, Hiroshi Kimura, Keiji Ohtsuki

  Elsevier BV, May 2022, Icarus, 378, 114920 - 114920, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Disruption of Saturn's ring particles by thermal stress

  Naoyuki Hirata, Ryuji Morishima, Keiji Ohtsuki, Akiko M. Nakamura

  Elsevier BV, May 2022, Icarus, 378, 114919 - 114919, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Electrostatic dust ejection from asteroid (3200) Phaethon with the aid of mobile alkali ions at perihelion

  Hiroshi Kimura, Katsuhito Ohtsuka, Shota Kikuchi, Keiji Ohtsuki, Tomoko Arai, Fumi Yoshida, Naoyuki Hirata, Hiroki Senshu, Koji Wada, Takayuki Hirai, Peng K. Hong, Masanori Kobayashi, Ko Ishibashi, Manabu Yamada, Takaya Okamoto

  Elsevier BV, Apr. 2022, Icarus, 382, 115022 - 115022, English

  [Refereed]

  Scientific journal


• FOSSIL. II. The Rotation Periods of Small-sized Hilda Asteroids

  Chan-Kao Chang, Ying-Tung Chen, Wesley C. Fraser, Matthew J. Lehner, Shiang-Yu Wang, Mike Alexandersen, Young-Jun Choi, A. Paula Granados Contreras, Takashi Ito, Youngmin JeongAhn, Jianghui Ji, J. J. Kavelaars, Myung-Jin Kim, Samantha M. Lawler, Jian Li, Zhong-Yi Lin, Patryk Sofia Lykawka, Hong-Kyu Moon, Surhud More, Marco Muñoz-Gutiérrez, Keiji Ohtsuki, Rosemary E. Pike, Tsuyoshi Terai, Seitaro Urakawa, Fumi Yoshida, Hui Zhang, Haibin Zhao, Ji-Lin Zhou

  American Astronomical Society, Mar. 2022, The Astrophysical Journal Supplement Series, 259(1) (1), 7 - 7, English

  [Refereed]

  Scientific journal


• Size Distributions of Bluish and Reddish Small Main-belt Asteroids Obtained by Subaru/Hyper Suprime-Cam*

  Natsuho Maeda, Tsuyoshi Terai, Keiji Ohtsuki, Fumi Yoshida, Kosuke Ishihara, Takuto Deyama

  We performed a wide-field survey observation of small asteroids using the Hyper Suprime-Cam installed on the 8.2 m Subaru Telescope. We detected more than 3000 main-belt asteroids with a detection limit of 24.2 mag in the r-band, which were classified into two groups (bluish C-like and reddish S-like) by the g–r color of each asteroid and obtained size distributions of each group. We found that the shapes of the size distributions of asteroids with C-like and S-like colors agree with each other in the size range of 0.4–5 km in diameter. Assuming the asteroid population in this size range is under collision equilibrium, our results indicate that compositional difference hardly affects the size dependence of impact strength, at least for the size range between several hundred meters and several kilometers. This size range corresponds to the size range of “spin barrier,” an upper limit observed in the rotation rate distribution. Our results are consistent with the view that most asteroids in this size range have a rubble-pile structure.

  American Astronomical Society, Dec. 2021, The Astronomical Journal, 162(6) (6), 280 - 280, English

  [Refereed]

  Scientific journal


• FOSSIL. I. The spin rate limit of Jupiter Trojans

  Chan-Kao Chang, Ying-Tung Chen, Wesley C. Fraser, Fumi Yoshida, Matthew J. Lehner, Shiang-Yu Wang, JJ Kavelaars, Rosemary E. Pike, Mike Alexandersen, Takashi Ito, Young-Jun Choi, A. Paula Granados Contreras, Youngmin JeongAhn, Jianghui Ji, Myung-Jin Kim, Samantha M. Lawler, Jian Li, Zhong-Yi Lin, Patryk Sofia Lykawka, Hong-Kyu Moon, Surhud More, Marco A. Muñoz-Gutiérrez, Keiji Ohtsuki, Tsuyoshi Terai, Seitaro Urakawa, Hui Zhang, Haibin Zhao, Ji-Lin Zhou

  American Astronomical Society, Oct. 2021, The Planetary Science Journal, 2(5) (5), 191 - 191, English

  [Refereed]

  Scientific journal


• A global system of furrows on Ganymede indicative of their creation in a single impact event

  Naoyuki Hirata, Ryo Suetsugu, Keiji Ohtsuki

  Dec. 2020, Icarus, 352, 113941 - 113941, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Delivery of Pebbles from the Protoplanetary Disk into Circumplanetary Disks

  Toru Homma, Keiji Ohtsuki, Natsuho Maeda, Ryo Suetsugu, Masahiro N. Machida, Takayuki Tanigawa

  Corresponding, American Astronomical Society, Nov. 2020, The Astrophysical Journal, 903(2) (2), 98 - 98, English

  [Refereed]

  Scientific journal


• Size of the smallest particles in Saturn's rings

  Ohtsuki, K, Kawamura, H, Hirata, N, Daisaka, H, Kimura, H

  Lead, Elsevier BV, Jul. 2020, Icarus, 344, 113346 - 113346, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A Comparative study of size frequency distributions of Jupiter Trojans, Hildas, and main-belt asteroids: A clue to planet migration history

  F. Yoshida, T. Terai, T. Ito, K. Ohtsuki, P. S. Lykawka, T. Hiroi, N. Takato

  May 2019, Planet. Space Sci, 169, 78 - 85, English

  [Refereed]

  Scientific journal


• Colors of Centaurs observed by the Subaru Hyper Suprime-Cam and implications for their origin

  H. Sakugawa, T. Terai, K. Ohtsuki, F. Yoshida, N. Takato, P. S. Lykawka, S.-Y. Wang

  Corresponding, Oct. 2018, Publ. Astron. Soc. Japan, 70(6) (6), 116, English

  [Refereed]

  Scientific journal


• Computer simulations of planetary rings

  Heikki Salo, Keiji Ohtsuki, Mark C. Lewis

  Cambridge University Press, Mar. 2018, Planetary Ring Systems: Properties, Structure, and Evolution, 434 - 493, English, International magazine, Co-authored internationally

  [Refereed][Invited]

  In book


• Multi-band photometry of trans-Neptunian objects in the Subaru Hyper Suprime-Cam survey

  Tsuyoshi Terai, Fumi Yoshida, Keiji Ohtsuki, Patryk Sofia Lykawka, Naruhisa Takato, Arika Higuchi, Takashi Ito, Yutaka Komiyama, Satoshi Miyazaki, Shiang-Yu Wang

  Oxford University Press, Jan. 2018, Publications of the Astronomical Society of Japan, 70(Special Issue 1) (Special Issue 1), S40, English

  [Refereed]

  Scientific journal


• Distribution of Captured Planetesimals in Circumplanetary Gas Disks and Implications for Accretion of Regular Satellites

  Ryo Suetsugu, Keiji Ohtsuki

  Apr. 2017, ASTROPHYSICAL JOURNAL, 839(1) (1), 66, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Diverse ring systems around giant planets

  Hyodo Ryuki, Charnoz Sébastien, Ohtsuki Keiji, Genda Hidenori

  本研究では, 約38 億年前に起こったと考えられている後期重爆撃期に, 冥王星サイズの巨大な微惑星が巨大惑星と少なくとも数回の近接遭遇を経験しうることに着目し, SPH計算とN体計算を用いて, 分化した微惑星の近接遭遇時の潮汐破壊過程，および，惑星に捕獲された破片の長期進化を詳細に調べることで, リングの形成可能性について議論する.

  The Japanese Society for Planetary Sciences, 2017, Planetary People - The Japanese Society for Planetary Sciences, 26(3) (3), 82 - 91, Japanese


• Report of the 5th Workshop on Satellite Systems

  Tanigawa Takayuki, Kimura Jun, Okuzumi Satoshi, Sekine Yasuhito, Kuramoto Kiyoshi, Ohtsuki Keiji, Tanaka Hidekazu

  The Japanese Society for Planetary Sciences, 2017, Planetary People - The Japanese Society for Planetary Sciences, 26(4) (4), 190 - 191, Japanese


• Ring formation around giant planets by tidal disruption of a single passing large Kuiper belt object

  Ryuki Hyodo, Sebastien Charnoz, Keiji Ohtsuki, Hidenori Genda

  Jan. 2017, ICARUS, 282, 195 - 213, English

  [Refereed]

  Scientific journal


• FORMATION OF CENTAURS' RINGS THROUGH THEIR PARTIAL TIDAL DISRUPTION DURING PLANETARY ENCOUNTERS

  Ryuki Hyodo, Sebastien Charnoz, Hidenori Genda, Keiji Ohtsuki

  Sep. 2016, ASTROPHYSICAL JOURNAL LETTERS, 828(1) (1), L8, English

  [Refereed]

  Scientific journal


• ORBITAL CHARACTERISTICS OF PLANETESIMALS CAPTURED BY CIRCUMPLANETARY GAS DISKS

  Ryo Suetsugu, Keiji Ohtsuki, Tetsuya Fujita

  Jun. 2016, ASTRONOMICAL JOURNAL, 151(6) (6), 140, English

  [Refereed]

  Scientific journal


• CAPTURE OF PLANETESIMALS BY WANING CIRCUMPLANETARY GAS DISKS

  Ryo Suetsugu, Keiji Ohtsuki

  Apr. 2016, ASTROPHYSICAL JOURNAL, 820(2) (2), 128, English

  [Refereed]

  Scientific journal


• Saturn's F ring and shepherd satellites a natural outcome of satellite system formation

  Ryuki Hyodo, Keiji Ohtsuki

  Sep. 2015, NATURE GEOSCIENCE, 8(9) (9), 686 - +, English

  [Refereed]

  Scientific journal


• FORMATION OF MULTIPLE-SATELLITE SYSTEMS FROM LOW-MASS CIRCUMPLANETARY PARTICLE DISKS

  Ryuki Hyodo, Keiji Ohtsuki, Takaaki Takeda

  Jan. 2015, ASTROPHYSICAL JOURNAL, 799(1) (1), 40, English

  [Refereed]

  Scientific journal


• GRAVITATIONAL ACCRETION OF PARTICLES ONTO MOONLETS EMBEDDED IN SATURN's RINGS

  Yuki Yasui, Keiji Ohtsuki, Hiroshi Daisaka

  Dec. 2014, ASTROPHYSICAL JOURNAL, 797(2) (2), 15, English

  [Refereed]

  Scientific journal


• COLLISIONAL DISRUPTION OF GRAVITATIONAL AGGREGATES IN THE TIDAL ENVIRONMENT

  Ryuki Hyodo, Keiji Ohtsuki

  May 2014, ASTROPHYSICAL JOURNAL, 787(1) (1), 14, English

  [Refereed]

  Scientific journal


• CAPTURE OF PLANETESIMALS BY GAS DRAG FROM CIRCUMPLANETARY DISKS

  Tetsuya Fujita, Keiji Ohtsuki, Takayuki Tanigawa, Ryo Suetsugu

  Dec. 2013, ASTRONOMICAL JOURNAL, 146(6) (6), 140, English

  [Refereed]

  Scientific journal


• Accretion rates of moonlets embedded in circumplanetary particle disks

  Keiji Ohtsuki, Yuki Yasui, Hiroshi Daisaka

  Aug. 2013, Astronomical Journal, 146(2) (2), 12, English

  [Refereed]

  Scientific journal


• Temporary capture of planetesimals by a giant planet and implication for the origin of irregular satellites

  Ryo Suetsugu, Keiji Ohtsuki

  2013, Monthly Notices of the Royal Astronomical Society, 431(2) (2), 1709 - 1718, English

  [Refereed]

  Scientific journal


• VISCOSITY IN PLANETARY RINGS WITH SPINNING SELF-GRAVITATING PARTICLES

  Yuki Yasui, Keiji Ohtsuki, Hiroshi Daisaka

  May 2012, ASTRONOMICAL JOURNAL, 143(5) (5), English

  [Refereed]

  Scientific journal


• DISTRIBUTION OF ACCRETING GAS AND ANGULAR MOMENTUM ONTO CIRCUMPLANETARY DISKS

  Takayuki Tanigawa, Keiji Ohtsuki, Masahiro N. Machida

  Mar. 2012, ASTROPHYSICAL JOURNAL, 747(1) (1), English

  [Refereed]

  Scientific journal


• Collisions and Gravitational Interactions between Particles in Planetary Rings

  Keiji Ohtsuki

  2012, PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, 195, 29-47(195) (195), 29 - 47, English

  [Refereed]

  Scientific journal


• TEMPORARY CAPTURE OF PLANETESIMALS BY A PLANET FROM THEIR HELIOCENTRIC ORBITS

  Ryo Suetsugu, Keiji Ohtsuki, Takayuki Tanigawa

  Dec. 2011, ASTRONOMICAL JOURNAL, 142(6) (6), English

  [Refereed]

  Scientific journal


• A multilayer model for thermal infrared emission of Saturn's rings. III: Thermal inertia inferred from Cassini CIRS

  Ryuji Morishima, Linda Spilker, Keiji Ohtsuki

  Sep. 2011, ICARUS, 215(1) (1), 107 - 127, English

  [Refereed]

  Scientific journal


• 周惑星円盤の形成：衛星系形成過程の解明へ向けて

  谷川 享行, OHTSUKI KEIJI, 町田 正博

  2011, 遊星人, 20, 262-270, Japanese

  [Refereed]

  Scientific journal


• A multilayer model for thermal infrared emission of Saturn's rings II: Albedo, spins, and vertical mixing of ring particles inferred from Cassini CIRS

  Ryuji Morishima, Linda Spilker, Heikki Salo, Keiji Ohtsuki, Nicolas Altobelli, Stuart Pilortz

  Nov. 2010, ICARUS, 210(1) (1), 330 - 345, English

  [Refereed]

  Scientific journal


• Accretion rates of planetesimals by protoplanets embedded in nebular gas

  Takayuki Tanigawa, Keiji Ohtsuki

  Feb. 2010, ICARUS, 205(2) (2), 658 - 673, English

  [Refereed]

  Scientific journal


• Mass dispersal and angular momentum transfer during collisions between rubble-pile asteroids. II. Effects of initial rotation and spin-down through disruptive collisions

  Takaaki Takeda, Keiji Ohtsuki

  Aug. 2009, ICARUS, 202(2) (2), 514 - 524, English

  [Refereed]

  Scientific journal


• A multilayer model for thermal infrared emission of Saturn's rings: Basic formulation and implications for Earth-based observations

  Ryuji Morishima, Heikki Salo, Keiji Ohtsuki

  Jun. 2009, ICARUS, 201(2) (2), 634 - 654, English

  [Refereed]

  Scientific journal


• Spin rates of fast-rotating asteroids and fragments in impact disruption

  Toshihiko Kadono, Masahiko Arakawa, Takashi Ito, Keiji Ohtsuki

  Apr. 2009, ICARUS, 200(2) (2), 694 - 697, English

  [Refereed]

  Scientific journal


• Satellite Formation: Supply of Solid Material to Circumplanetary Disks

  Takayuki Tanigawa, Keiji Ohtsuki, Hiroshi Kobayashi

  2009, EXOPLANETS AND DISKS: THEIR FORMATION AND DIVERSITY, 1158, 269 - +, English

  [Refereed]

  International conference proceedings


• Dynamics of saturn's dense rings

  Jürgen Schmidt, Keiji Ohtsuki, Nicole Rappaport, Heikki Salo, Frank Spahn

  Springer Netherlands, 2009, Saturn from Cassini-Huygens, 413-458, 413 - 458, English

  [Refereed]

  In book


• Mass dispersal and angular momentum transfer during collisions between rubble-pile asteroids

  Takaaki Takeda, Keiji Ohtsuki

  Jul. 2007, ICARUS, 189(1) (1), 256 - 273, English

  [Refereed]

  Scientific journal


• Dynamical behaviour of planetesimals temporarily captured by a planet from heliocentric orbits: basic formulation and the case of low random velocity

  Kazunori Iwasaki, Keiji Ohtsuki

  Jun. 2007, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 377(4) (4), 1763 - 1771, English

  [Refereed]

  Scientific journal


• Rotation rate and velocity dispersion of planetary ring particles with size distribution I. Formulation and analytic calculation

  Keiji Ohtsuki

  Aug. 2006, ICARUS, 183(2) (2), 373 - 383, English

  [Refereed]

  Scientific journal


• Rotation rate and velocity dispersion of planetary ring particles with size distribution II. Numerical simulation for gravitating particles

  Keiji Ohtsuki

  Aug. 2006, ICARUS, 183(2) (2), 384 - 395, English

  [Refereed]

  Scientific journal


• Orbital stability of protoplanetary systems in nebular gas and implications for terrestrial planet formation

  K Iwasaki, K Ohtsuki

  Jun. 2006, ASTRONOMICAL JOURNAL, 131(6) (6), 3093 - 3099, English

  [Refereed]

  Scientific journal


• Local N-body simulations for the rotation rates of particles in planetary rings

  K Ohtsuki, D Toyama

  Sep. 2005, ASTRONOMICAL JOURNAL, 130(3) (3), 1302 - 1310, English

  [Refereed]

  Scientific journal


• Rotation rates of particles in Saturn's rings

  K Ohtsuki

  Jun. 2005, ASTROPHYSICAL JOURNAL, 626(1) (1), L61 - L64, English

  [Refereed]

  Scientific journal


• On the rotation of a moonlet embedded in planetary rings

  K Ohtsuki

  Dec. 2004, ICARUS, 172(2) (2), 432 - 445, English

  [Refereed]

  Scientific journal


• On the isotopic fractionation of terrestrial xenon by gravitational separation inside porous planetesimals with size distribution

  K Ohtsuki, A Takahashi, M Sano

  2004, GEOCHEMICAL JOURNAL, 38(5) (5), 455 - 460, English

  [Refereed]

  Scientific journal


• Formulation and analytic calculation for the spin angular momentum of a moonlet due to inelastic collisions of ring particles

  K Ohtsuki

  2004, EARTH PLANETS AND SPACE, 56(9) (9), 909 - 919, English

  [Refereed]

  Scientific journal


• Semi-analytic formulas of velocity stirring rates in particle disks

  K Ohtsuki, GR Stewart, S Ida

  2004, PLANETARY SYSTEMS IN THE UNIVERSE OBSERVATION, FORMATION AND EVOLUTION, (202) (202), 229 - 231, English

  [Refereed]

  Scientific journal


• Radial diffusion rate of planetesimals due to gravitational encounters

  K Ohtsuki, H Tanaka

  Mar. 2003, ICARUS, 162(1) (1), 47 - 58, English

  [Refereed]

  Scientific journal


• A new formulation of the viscosity in planetary rings

  H Tanaka, K Ohtsuki, H Daisaka

  Jan. 2003, ICARUS, 161(1) (1), 144 - 156, English

  [Refereed]

  Scientific journal


• Evolution of planetesimal velocities based on three-body orbital integrations and growth of protoplanets

  K Ohtsuki, GR Stewart, S Ida

  Feb. 2002, ICARUS, 155(2) (2), 436 - 453, English

  [Refereed]

  Scientific journal


• Evaluation of collision and stirring rates in circumplanetary particle disks based on three-body orbital integrations

  K Ohtsuki

  May 2000, PLANETARY AND SPACE SCIENCE, 48(6) (6), 553 - 568, English

  [Refereed]

  Scientific journal


• Origin and Evolution of Terrestrial Planet Rotation

  Lissauer, J. J., Dones, L., Ohtsuki, K.

  University of Arizona Press, 2000, Origin of the Earth and Moon, 101 - 112, English

  [Refereed]

  In book


• Local N-body simulations for the distribution and evolution of particle velocities in planetary rings

  K Ohtsuki, H Emori

  Jan. 2000, ASTRONOMICAL JOURNAL, 119(1) (1), 403 - 416, English

  [Refereed]

  Scientific journal


• High-accuracy statistical simulation of planetary accretion: I. Test of the accuracy by comparison with the solution to the stochastic coagulation equation

  S Inaba, H Tanaka, K Ohtsuki, K Nakazawa

  1999, EARTH PLANETS AND SPACE, 51(3) (3), 205 - 217, English

  [Refereed]

  Scientific journal


• Evolution of particle velocity dispersion in a circumplanetary disk due to inelastic collisions and gravitational interactions

  K Ohtsuki

  Jan. 1999, ICARUS, 137(1) (1), 152 - 177, English

  [Refereed]

  Scientific journal


• Planetary rotation by accretion of planetesimals with nonuniform spatial distribution formed by the planet's gravitational perturbation

  K Ohtsuki, S Ida

  Feb. 1998, ICARUS, 131(2) (2), 393 - 420, English

  [Refereed]

  Scientific journal


• Accretional evolution of a planetesimal swarm .2. The terrestrial zone

  SJ Weidenschilling, D Spaute, DR Davis, F Marzari, K Ohtsuki

  Aug. 1997, ICARUS, 128(2) (2), 429 - 455, English

  [Refereed]

  Scientific journal


• CAPTURE PROBABILITY OF COLLIDING PLANETESIMALS - DYNAMICAL CONSTRAINTS ON ACCRETION OF PLANETS, SATELLITES, AND RING PARTICLES

  K OHTSUKI

  Nov. 1993, ICARUS, 106(1) (1), 228 - 246, English

  [Refereed]

  Scientific journal


• Planetary accretion in the solar gravitational field

  Ohtsuki, K, S. Ida, Y. Nakagawa, K. Nakazawa

  University of Arizona Press, 1993, Protostars and planets III, 1089 - 1107, English

  [Refereed]

  In book


• EVOLUTION OF RANDOM VELOCITIES OF PLANETESIMALS IN THE COURSE OF ACCRETION

  K OHTSUKI

  Jul. 1992, ICARUS, 98(1) (1), 20 - 27, English

  [Refereed]

  Scientific journal


• EQUILIBRIUM VELOCITIES IN PLANETARY RINGS WITH LOW OPTICAL DEPTH

  K OHTSUKI

  Feb. 1992, ICARUS, 95(2) (2), 265 - 282, English

  [Refereed]

  Scientific journal


• RUNAWAY PLANETARY GROWTH WITH COLLISION RATE IN THE SOLAR GRAVITATIONAL-FIELD

  K OHTSUKI, S IDA

  Jun. 1990, ICARUS, 85(2) (2), 499 - 511, English

  [Refereed]

  Scientific journal


• KINETIC-BEHAVIOR OF PLANETESIMALS REVOLVING AROUND THE SUN

  K OHTSUKI, K NAKAZAWA, Y NAKAGAWA

  1990, SMALLER SOLAR SYSTEM BODIES AND ORBITS, 10(3-4) (3-4), 105 - 108, English

  [Refereed]

  International conference proceedings


• ARTIFICIAL ACCELERATION IN ACCUMULATION DUE TO COARSE MASS-COORDINATE DIVISIONS IN NUMERICAL-SIMULATION

  K OHTSUKI, Y NAKAGAWA, K NAKAZAWA

  Jan. 1990, ICARUS, 83(1) (1), 205 - 215, English

  [Refereed]

  Scientific journal


• GROWTH OF THE EARTH IN NEBULAR GAS

  K OHTSUKI, Y NAKAGAWA, K NAKAZAWA

  Sep. 1988, ICARUS, 75(3) (3), 552 - 565, English

  [Refereed]

  Scientific journal


• GRAVITATIONAL SCATTERING BETWEEN PLANETESIMALS AND THEIR STATISTICAL BEHAVIOR

  M HASEGAWA, K OHTSUKI, K NAKAZAWA, Y NAKAGAWA

  1988, PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, 96(96) (96), 175 - 195, English

  [Refereed]

  Scientific journal


• DISSIPATION OF THE SOLAR NEBULA

  K OHTSUKI, Y NAKAGAWA

  1988, PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, 96(96) (96), 161 - 166, English

  [Refereed]

  Scientific journal


• ACCUMULATION PROCESS OF PLANETESIMALS TO THE PLANETS

  K OHTSUKI, Y NAKAGAWA

  1988, PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, 96(96) (96), 239 - 255, English

  [Refereed]

  Scientific journal

• 土星の環は何を語るか

  OHTSUKI KEIJI

  丸善出版株式会社, Apr. 2018, パリティ, 33(4) (4), 20 - 24, Japanese

  [Refereed][Invited]

  Introduction commerce magazine


• 鉄隕石の起源：宇宙を漂い故郷に帰る小さな鉄の旅人

  OHTSUKI KEIJI

  一般社団法人 日本鉄鋼協会, Dec. 2017, ふぇらむ, 22(12) (12), 16 - 19, Japanese

  Introduction other


• 宇宙でぺたっとくっついてできた彗星

  OHTSUKI KEIJI

  丸善出版, May 2016, パリティ, 31(4) (4), 38 - 40, Japanese


• Report of Workshop on Satellite Systems 2015

  Tanigawa T, Kimura J, Sekine Y, Kuramoto K, Ohtsuki K

  日本惑星科学会, Dec. 2015, Planetary People, 24(4) (4), 343 - 345, Japanese


• Report of Workshop on Satellite Systems

  Tanigawa T., Okuzumi S., Kimura J., Kuramoto K., Ohtsuki K.

  The Japanese Society for Planetary Sciences, Dec. 2014, Planetary People, 23(4) (4), 386 - 388, Japanese


• P1-18 周惑星粒子円盤の進化と衛星系の多様性(ポスターセッション1,ポスター発表)

  兵頭 龍樹, 大槻 圭史, 武田 隆顕

  日本惑星科学会, 10 Sep. 2014, 日本惑星科学会秋期講演会予稿集, 2014, "P1 - 18", Japanese


• O12-04 ラブルパイル小衛星の衝突破壊による土星Fリングの形成(口頭発表セッション12 衝突実験II,口頭発表)

  兵頭 龍樹, 大槻 圭史

  日本惑星科学会, 10 Sep. 2014, 日本惑星科学会秋期講演会予稿集, 2014, "O12 - 04", Japanese


• Report of Workshop on Satellite Systems

  Tanigawa T, Okuzumi S, Kimura J, Kuramoto K, Ohtsuki K

  日本惑星科学会, Dec. 2013, Planetary People, 22(4) (4), 274 - 276, Japanese


• O6-04 惑星周りの粒子円盤の進化と衛星形成(口頭発表セッション6(衛星系・リング),口頭発表)

  兵頭 龍樹, 大槻 圭史, 武田 隆顕

  日本惑星科学会, 20 Nov. 2013, 日本惑星科学会秋期講演会予稿集, 2013, "O6 - 04", Japanese


• Report of the Mini Workshop on the Formation of Satellite Systems

  TANIGAWA T., OKUZUMI S., KURAMOTO K., OHTSUKI K.

  The Japanese Society for Planetary Sciences, 25 Dec. 2012, Planetary People, 21(4) (4), 377 - 379, Japanese


• O9-07 周惑星円盤から受けるガス抵抗による微惑星捕獲(口頭発表セッション9(惑星形成論II),口頭発表)

  藤田 哲也, 大槻 圭史, 谷川 享行

  日本惑星科学会, 24 Oct. 2012, 日本惑星科学会秋期講演会予稿集, 2012, 82 - 82, Japanese


• O9-06 巨大惑星による微惑星一時捕獲過程(口頭発表セッション9(惑星形成論II),口頭発表)

  末次 竜, 大槻 圭史

  日本惑星科学会, 24 Oct. 2012, 日本惑星科学会秋期講演会予稿集, 2012, 81 - 81, Japanese


• S31-01 惑星による微惑星一時捕獲過程(口頭セッション31:惑星形成の力学過程,口頭発表)

  末次 竜, 大槻 圭史, 谷川 享行

  日本惑星科学会, 23 Oct. 2011, 日本惑星科学会秋期講演会予稿集, 2011, 64 - 64, Japanese


• S23-01 原始衛星系円盤の形成 : 原始惑星系円盤からのガス降着流の解析(口頭セッション23:原始惑星系円盤,口頭発表)

  谷川 享行, 大槻 圭史, 町田 正博

  日本惑星科学会, 23 Oct. 2011, 日本惑星科学会秋期講演会予稿集, 2011, 53 - 53, Japanese


• Strategic study of lunar and planetary explorations in coming decade

  NAMIKI Noriyuki, KOBAYASHI Naoki, DEMURA Hirohide, OHTSUKI Keiji

  本稿では日本惑星科学会の将来惑星探査検討グループで行っている『月惑星探査の来たる10年』検討を紹介する.この検討活動は惑星探査の長期的な展望を検討するものであり,惑星科学のコミュニティが,自らの責任において将来像を描いていく作業である.検討は三つの段階に分けて行う.トップサイエンスを抽出する第一段階,ミッション・観測機器提案の科学的重要性を評価する第二段階,ミッション・観測機器提案の実現性を評価する第三段階である.各段階では,学会講演会,シンポジウム等の機会を利用してコミュニティからの意見聴取を行い,検討にフィードバックする.

  The Japanese Society for Planetary Sciences, 25 Sep. 2010, Planetary people, 19(3) (3), 221 - 227, Japanese


• 220 周惑星ガス円盤による微惑星捕獲 : 解析的見積もり(オーラルセッション8 原始惑星系円盤・惑星形成)

  谷川 享行, 大槻 圭史, 小林 浩

  日本惑星科学会, 28 Sep. 2009, 日本惑星科学会秋期講演会予稿集, 2009, 48 - 48, Japanese


• 103 原始衛星系円盤への固体物質の供給 : 周惑星ガス円盤による微惑星捕獲(惑星の形成および惑星大気,オーラルセッション1)

  谷川 享行, 大槻 圭史, 町田 正博

  日本惑星科学会, 01 Nov. 2008, 日本惑星科学会秋期講演会予稿集, 2008, 3 - 3, Japanese


• Planetary rings: particle properties and evolution

  大槻 圭史, 台坂 博, 武田 隆顕

  リング・衛星系は巨大惑星形成過程の自然な副産物であると考えられる．本稿では，土星リングを構成する氷粒子の物性がリングの力学進化や構造形成に及ぼす影響について述べる．氷粒子の反発係数はリングの力学進化を考える上で重要な物理量であり，室内実験結果が理論研究に使われてきた．粒子表面の摩擦は粒子自転を引き起こし，土星リングからの熱輻射の観測結果を解釈する上で重要となる．また粒子間の非重力的吸着力がリングの進化や構造形成に及ぼす影響，隕石衝突によるリング組成進化に関する研究等も行なわれているが，これらについては今後さらに詳しく調べる必要がある．All the four giant planets in our Solar System have rings, thus ring-satellite systems seem to be a natural byproduct of giant planet formation process. Therefore, studies on the origin and evolution of ring-satellite systems would constrain the formation processes of giant planets. Saturn's rings are mainly composed of water ice, and particles in the main rings have sizes between centimeters to several meters. We first describe effects of normal and tangential coefficients of restitution of icy ring particles on dynamical evolution of planetary rings. Restitution coefficients for icy particles for low-velocity impacts relevant to Saturn's rings have been measured by laboratory impact experiments. Restitution coefficients influence random velocity evolution of ring particles, their rotational states, and accretional evolution. We will also discuss possible effects of adhesive forces between ring particles on accretional evolution and structure formation in rings, although it is not clear at present whether nongravitational cohesive forces would play a major role in the dynamics of planetary rings. Finally, we will discuss effects of meteoroid impacts on the creation and evolution of planetary rings. Dilute dust rings including the Jovian rings are created by meteoroid impacts on small satellites. Such impacts would also cause compositional evolution of Saturn's rings. Further theoretical as well as observational studies of compositional evolution of Saturn's rings would provide a unique constraint on the origin and evolution of the rings.

  北海道大学低温科学研究所, 2007, Low temperature science, 66, 73 - 81, Japanese

• 太陽系と惑星

  編者, 井田, 茂, 渡部, 潤一, 佐々木, 晶

  Contributor, 日本評論社, Aug. 2021, Japanese, ISBN: 9784535607613


• 天文学辞典

  編者, 岡村, 定矩, 家, 正則, 犬塚, 修一郎, 小山, 勝二, 千葉, 柾司, 富阪, 幸治

  Contributor, 日本評論社, Jul. 2012, Japanese, ISBN: 9784535607385

• Propeller- and Gap-Forming Planetesimals in White Dwarf Debris Discs

  Rafael Martinez-Brunner, Dimitri Veras, Rebecca Nealon, Keiji Ohtsuki, Takato Nishio, Ryo Tamon

  UK Exoplanet Meeting 2026, Mar. 2026, English

  Poster presentation


• Exploring white dwarfs debris discs with SPH

  Rafael Martinez-Brunner, Dimitri Veras, Rebecca Nealon, Ayaka Okuya, Cristiano Longarini, Keiji Ohtsuki, Takato Nishio, Ryo Tamon, Daniel Price

  UK White Dwarf Science Meeting, Mar. 2026, English

  Oral presentation


• Global N-body simulation of propeller formation in Saturn's rings

  Ryo Tamon, Keiji Ohtsuki

  57th Lunar and Planet. Sci. Conf, Mar. 2026, English

  Poster presentation


• Influence of target's gravity on ejecta dynamics and change in asteroid velocity

  Takato Nishio, Keiji Ohtsuki, Keisuke Sugiura

  57th Lunar and Planet. Sci. Conf, Mar. 2026, English

  Poster presentation


• 小規模破壊衝突におけるエジェクタの解析

  西尾峻人, 大槻圭史, 杉浦圭祐

  衝突研究会, Nov. 2025, Japanese

  Oral presentation


• Small-Scale Structures in Saturn's Rings

  Keiji Ohtsuki

  The First OPENS International Science Workshop, Sep. 2025, English

  [Invited]

  Invited oral presentation


• 土星リング粒子の衝突過程における微粒子放出のシミュレーション

  藤原大揮, 大槻圭史, 田中秀和

  日本惑星科学会2025年秋季講演会, Sep. 2025, Japanese

  Poster presentation


• 原始惑星系円盤から周惑星円盤へのガス降着における初期高度と降着位置の関係

  野﨑智仁, 谷川享行, 大槻圭史, 前田夏穂

  日本惑星科学会2025年秋季講演会, Sep. 2025, Japanese

  Poster presentation


• 周惑星円盤に捕獲された微惑星の軌道進化

  多門瞭, 大槻圭史, 末次竜

  日本惑星科学会2025年秋季講演会, Sep. 2025, Japanese

  Poster presentation


• 小規模破壊による小惑星の速度変化

  西尾峻人, 大槻圭史, 杉浦圭祐

  日本惑星科学会2025年秋季講演会, Sep. 2025, Japanese

  Poster presentation


• 破壊を伴う衝突により小惑星の速度はどのようにかわるのか

  西尾峻人, 大槻圭史, 杉浦圭祐

  日本地球惑星科学連合2025年大会, May 2025, Japanese

  Poster presentation


• 微惑星合体条件のサイズ依存性

  中原蒼大, 大槻圭史, 杉浦圭祐, 玄田英典, 黒崎健二, 末次竜

  日本地球惑星科学連合2025年大会, May 2025, English

  Poster presentation


• Numerical Simulation for Velocity Changes After a Disruptive Impact Between Asteroids

  Takato Nishio, Keiji Ohtsuki, Keisuke Sugiura

  Hera, Apophis T-4, and RAMSES in Tokyo 2025, Apr. 2025, English

  Poster presentation


• Change in asteroid velocity due to disruptive impact

  Takato Nishio, Keiji Ohtsuki, Keisuke Sugiura

  56th Lunar and Planet. Sci. Conf, Mar. 2025, English

  Poster presentation


• Change in asteroid velocity due to disruptive impact

  Takato Nishio, Keiji Ohtsuki, Keisuke Sugiura

  Circumplanetary Disks and Satelite Formation III, Jan. 2025, English

  Poster presentation


• 破壊を伴う衝突による小惑星速度変化

  西尾峻人, 大槻圭史, 杉浦圭祐

  衝突研究会, Nov. 2024, Japanese

  Oral presentation


• 破壊を伴う衝突による小惑星速度変化

  西尾峻人, 大槻圭史, 杉浦圭祐

  日本惑星科学会2024年秋季講演会, Sep. 2024, Japanese

  Poster presentation


• 巨大惑星周惑星円盤への固体粒子供給及び微惑星合体条件の天体サイズ依存性

  大槻圭史

  新学術領域「星・惑星形成」2023年度大研究会, Dec. 2023, Japanese

  Oral presentation


• 巨大惑星の周惑星円盤へのガス・ダスト供給の惑星質量依存性

  前田夏穂, 大槻圭史, 末次竜, 芝池諭人, 谷川享行, 町田正博

  日本惑星科学会2023年秋季講演会, Oct. 2023, Japanese

  Oral presentation


• Change of Asteroid Rotation Rates by Disruptive Collisions

  Keiji Ohtsuki, Chihiro Semba, Keisuke Sugiura, Ryo Suetsugu

  Asteroids, Comets, Meteors Conference, Jun. 2023, English


• Change of asteroid rotation rates by collisional disruption: Implication for observation and collisional evolution

  Keiji Ohtsuki, Chihiro Semba, Keisuke Sugiura, Ryo Suetsugu

  Japan Geoscience Union Meeting 2023, May 2023, English

  Oral presentation


• 微惑星衝突における合体条件の天体サイズ依存性

  中原蒼大, 杉浦圭祐, 大槻圭史

  日本地球惑星科学連合大会2023年大会, May 2023, Japanese

  Poster presentation


• 周惑星円盤への衛星材料の供給：ダストの鉛直分布と原始惑星質量への依存性

  前田夏穂, 大槻圭史, 谷川享行, 町田正博, 末次竜

  日本地球惑星科学連合大会2023年大会, May 2023, Japanese

  Oral presentation


• Supply of satellite material into circumplanetary disks around giant planets

  Natsuho Maeda, Keiji Ohtsuki, Ryo Suetsugu, Masahiro N. Machida, Takayuki Tanigawa

  Protostar and Planets VII, Apr. 2023, English

  Poster presentation


• Size dependence of the Merging Criteria for Planetesimal Collision

  Sota Nakahara, Keisuke Sugiura, Keiji Ohtsuki

  Protostar and Planets VII, Apr. 2022, English

  Poster presentation


• 周惑星円盤への衛星材料供給：原始惑星質量・ダスト鉛直分布への依存性

  前田夏穂

  惑星形成討論会, Mar. 2023, Japanese

  Oral presentation


• 巨大惑星の周惑星円盤へのガス降着：３次元数値流体計算を用いた質量降着率の惑星質量依存性

  前田夏穂, 大槻圭史, 谷川享行, 町田正博, 末次竜

  日本惑星科学会2022年秋季講演会, Sep. 2022, Japanese

  Poster presentation


• Size distributions of small main belt asteroids obtained by the Subaru/Hyper Suprime-Cam

  Natsuho Maeda, T. Terai, K. Ohtsuki, F. Yoshida, K. Ishihara, T. Deyama

  日本地球惑星科学連合大会2022年大会, May 2022, English

  Poster presentation


• 巨大惑星周惑星円盤へのガス降着の解析及び原始惑星hit-and-run衝突のシミュレーション

  大槻圭史

  新学術領域「星・惑星形成」2021年度大研究会, Mar. 2022, Japanese

  Oral presentation


• 鉛直降着流による巨大 惑星の周惑星円盤への衛星材料物質供給

  前田夏穂, 大槻圭史, 末次竜, 町田正博, 谷川享行

  日本惑星科学会2021年秋季講演会, Sep. 2021, Japanese

  Poster presentation


• すばる望遠鏡 Hyper Suprime-Cam を用いたメインベルト小惑星の観測とサイズ分布の測定

  前田夏穂, 寺居剛, 大槻圭史, 吉田二美, 石原昂将, 出山拓門

  2021年度 第51回天文・天体物理若手夏の学校, Aug. 2021, Japanese

  Oral presentation


• Color and size distributions of main belt asteroids obtained by the Subaru/Hyper Suprime-Cam

  Maeda, N, T. Terai, K. Ohtsuki, F. Yoshida, K. Ishihara, T. Deyama

  Japan Geoscience Union Meeting 2021, Jun. 2021, English

  Oral presentation


• 巨大惑星系へのガス・微小粒子供 給と衛星形成

  前田夏穂, 大槻圭史, 末次竜, 町田正博

  日本地球惑星科学連合2021年大会, Jun. 2021, Japanese


• Size distributions of bluish and reddish small main belt asteroids

  N. Maeda, T. Terai, K. Ohtsuki, F. Yoshida, K. Ishihara, T. Deyama

  52nd Lunar and Planetary Science Conference, Mar. 2021, English

  Poster presentation


• Delivery of solids from the protoplanetary disk onto circumplanetary disks

  Keiji Ohtsuki

  Circumplanetary Disk and Satellite Formation II Conference, Mar. 2021, English

  [Invited]

  Invited oral presentation


• Supply of solid materials into a circumplanetary disk via vertical accreting gas flow

  N. Maeda, K.Ohtsuki, R. Suetsugu, M. N. Machida

  Circumplanetary Disk and Satellite Formation II Conference, Mar. 2021, English

  Poster presentation


• 3次元ガス流を考慮した周惑星円盤への衛星材料物質供給

  前田夏穂, 大槻圭史, 末次竜, 町田正博

  惑星系形成若手研究会, Feb. 2021, Japanese

  Oral presentation


• Accretion of gas and solid materials into the circumplanetary disk of a growing giant planet: Dependence on planetary mass

  前田夏穂, 寺居剛, 大槻圭史, 吉田二美, 石原昂将, 出山拓門

  日本惑星科学会2020年秋季講演会, Nov. 2020, Japanese

  Poster presentation


• Accretion of gas and solid materials into the circumplanetary disk of a growing giant planet: Dependence on planetary mass

  N. Maeda, K. Ohtsuki, R. Suetsugu, M. N. Machida

  JPGU-AGU joint Meeting 2020, Jul. 2020, English

  Poster presentation


• Accretion of Pebbles into the Circumplanetary Disk of a Giant Planet

  前田夏穂, 大槻圭史, 末次竜, 町田正博

  第２回水惑星国際スクール, Feb. 2020, English

  Poster presentation


• 巨大惑星の周惑星円盤へのダストの供給

  前田夏穂, 大槻圭史, 末次竜, 町田正博

  衛星系研究会2020, Feb. 2020, Japanese

  Oral presentation


• Accretion of Pebbles into the Circumplanetary Disk of a Giant Planet

  前田夏穂, 大槻圭史, 末次竜, 町田正博

  惑星圏研究会2020, Feb. 2020, English

  Poster presentation


• Accretion of pebbles into the circumplanetary disk of a giant planet

  前田夏穂, 大槻圭史, 末次竜, 町田正博, 谷川享行

  Planet Formation Workshop 2019, Nov. 2019, English

  Poster presentation


• Numerical simulation for the distribution of small bodies in circumplanetary disks supplied from the protoplanetary disk

  大槻圭史, 本間徹, 末次竜, 町田正博

  Planet Formation Workshop 2019, Nov. 2019, English

  Poster presentation


• 衝突によるラブルパイル天体の自転速度変化

  池田 晋太郎, 大槻 圭史, 末次 竜

  第15回衝突研究会 研究集会, Nov. 2019, 千葉工業大学 東京スカイツリータウンキャンパス, Domestic conference

  Oral presentation


• 衝突掘削による氷小天体カラーへの影響

  岩佐 海詩, 末次 竜, 大槻 圭史

  第15回衝突研究会 研究集会, Nov. 2019, 千葉工業大学 東京スカイツリータウンキャンパス, Domestic conference

  Oral presentation


• すばる望遠鏡Hyper Suprime-Camによる木星L5トロヤ群小惑星のサイズ分布測定

  上畑琴美、寺居剛、大槻圭史、吉田二美

  日本惑星科学会2019年秋季大会, Oct. 2019, Japanese

  Poster presentation


• A comparative study of size frequency distributions of Jupiter Trojans, Hildas and main belt asteroids: A clue to planet migration history

  吉田 二美, 寺居 剛, 伊藤 孝士, 大槻 圭史, Lykawka S. Patryk, 廣井 隆弘, 高遠 徳尚

  日本惑星科学会2019年秋季大会, Oct. 2019, 京都産業大学 神山ホール, Domestic conference

  Poster presentation


• 球対称ガス大気による微惑星の捕獲

  末次 竜, 大槻 圭史

  日本惑星科学会2019年秋季大会, Oct. 2019, 京都産業大学 神山ホール, Domestic conference

  Poster presentation


• Size of the Smallest Particles in Saturn's Rings

  Keiji Ohtsuki, Hiroshi Kawamura, Naoyuki Hirata, Hiroshi Daisaka, Hiroshi Kimura

  Japan Geoscience Union Meeting 2019, May 2019, English, Makuhari Messe, Chiba, International conference

  Poster presentation


• Size and color distributions of small main-belt asteroids observed by the Subaru/Hyper Suprime-Cam

  Takuto Deyama, Tsuyoshi Terai, Keiji Ohtsuki, Fumi Yoshida

  50th Lunar and Planetary Science Conference, Mar. 2019, English, The Woodlands Waterway Marriott Hotel and Convention Center, Texas, International conference

  Oral presentation


• Impact velocity between particles in saturn's rings

  H. Kawamura, K. Ohtsuki, N. Hirata, H. Daisaka

  50th Lunar and Planetary Science Conference, Mar. 2019, English, The Woodlands Waterway Marriott Hotel and Convention Center, Texas, International conference

  Oral presentation


• Distribution of small bodies in circumplanetary disks supplied from the protoplanetary disk

  Toru Homma, Keiji Ohtsuki, Ryo Suetsugu, Masahiro N. Machida, Taka-yuki Tanigawa

  50th Lunar and Planetary Science Conference, Mar. 2019, English, The Woodlands Waterway Marriott Hotel and Convention Center, Texas, International conference

  Oral presentation


• 土星環粒子に働く熱応力と粒径進化

  平田 直之, 大槻 圭史

  日本惑星科学会2018年秋季講演会, Oct. 2018, Japanese, 旭川市科学館サイパル, Domestic conference

  Oral presentation


• 原始惑星系円盤において鉛直方向に分布する小粒子の周惑星円盤への降着

  本間 徹, OHTSUKI KEIJI, 末次 竜, 町田 正博, 谷川 享行

  日本惑星科学会2018年秋季講演会, Oct. 2018, Japanese, 旭川市科学館サイパル, Domestic conference

  Oral presentation


• ガス抵抗によって捕獲された微惑星の軌道進化

  末次 竜, 大槻 圭史

  日本惑星科学会2018年秋季講演会, Oct. 2018, Japanese, 旭川市科学館サイパル, Domestic conference

  Oral presentation


• 土星リング粒子の衝突速度と最小粒子サイズ

  川村 浩司, 大槻 圭史, 平田 直之, 台坂 博

  日本天文学会2018年秋季年会, Sep. 2018, Japanese, 兵庫県立大学 姫路工学キャンパス, Domestic conference

  Oral presentation


• 赤外線天文衛星「あかり」近・中間赤外線カメラIRCの絶対強度較正の再解析

  出山 拓門, 臼井 文彦, 大槻 圭史, 山下 拓時, 江草 芙実

  日本天文学会2018年秋季年会, Sep. 2018, Japanese, 兵庫県立大学 姫路工学キャンパス, Domestic conference

  Oral presentation


• 原始惑星系円盤で鉛直方向に巻き上げられた小粒子の周惑星円盤への降着

  本間 徹, OHTSUKI KEIJI, 末次 竜, 町田 正博

  日本天文学会2018年秋季年会, Sep. 2018, Japanese, 兵庫県立大学 姫路工学キャンパス, Domestic conference

  Oral presentation


• The Formation of Spokes: The Role of Cohesion

  Naoyuki Hirata, Hiroshi Kimura, Keiji Ohtsuki

  Asia Oceania Geosciences Society(AOGS) 15th Annual Meeting, Jun. 2018, English, Honolulu, Hawaii, International conference

  Poster presentation


• Impact velocity between particles in Saturn’s rings and implications for the minimum particle size

  Keiji Ohtsuki, Hiroshi Kawamura, Naoyuki Hirata, Hiroshi Daisaka

  Asia Oceania Geosciences Society(AOGS) 15th Annual Meeting, Jun. 2018, English, Honolulu, Hawaii, International conference

  Poster presentation


• 土星環粒子・氷衛星上のボルダーに働く熱応力とその寿命

  平田 直之, 大槻 圭史

  日本地球惑星科学連合2018年大会, May 2018, Japanese, 幕張メッセ, Domestic conference

  Poster presentation


• Multi-band Photometry of Trans-Neptunian Objects in the Subaru Hyper Suprime-Cam Survey

  Tsuyoshi Terai, Fumi Yoshida, Keiji Ohtsuki, Patryk Sofia Lykawka, Naruhisa Takato, Arika Higuchi, Takashi Ito

  Japan Geoscience Union Meeting 2018, May 2018, English, Makuhari Messe, Chiba, International conference

  Poster presentation


• Dynamical constraints on the mass of the largest body captured in Jupiter's Trojan swarm

  Keiji Ohtsuki, Hiroaki Okayama

  Japan Geoscience Union Meeting 2018, May 2018, English, Makuhari Messe, Chiba, International conference

  Oral presentation


• Colors of Centaurs observed by the Subaru/Hyper Suprime-Cam

  Haruka Sakugawa, Tsuyoshi Terai, Keiji Ohtsuki, Fumi Yoshida

  Japan Geoscience Union Meeting 2018, May 2018, English, Makuhari Messe, Chiba, International conference

  Poster presentation


• Accretion of Vertically Stirred Small Bodies in the Protoplanetary Disk onto Circum-Planetary Disks

  Toru Homma, Keiji Ohtsuki, Ryo Suetsugu, Masahiro N. Machida

  Japan Geoscience Union Meeting 2018, May 2018, English, Makuhari Messe, Chiba, International conference

  Poster presentation


• Accretion of vertically stirred small bodies in the protoplanetary disk onto circumplanetary disks

  Toru Homma, Keiji Ohtsuki, Fumihiko Usui, Ryo Suetsugu, Masahiro N. Machida

  10th RESCEU/Planet2 symposium, Nov. 2017, English, Koshiba Hall, University of Tokyo, International conference

  Poster presentation


• Reanalysis for Absolute Photometric Calibration of the Infrared Camera (IRC) aboard AKARI

  Takuto Deyama, Fumihiko Usui, Ohtsuki Keiji

  AKARI Conference 2017, Oct. 2017, English, Ito Hall, The University of Tokyo, International conference

  Poster presentation


• 捕獲された微惑星の周惑星円盤内での分布

  末次 竜, OHTSUKI KEIJI

  JpGU-AGU Joint Meeting 2017, May 2017, Japanese, 幕張メッセ, International conference

  Poster presentation


• 巨大微惑星の潮汐破壊による巨大惑星リングの形成

  兵頭 龍樹, Charnoz Sebastien, OHTSUKI KEIJI, 玄田 英典

  JpGU-AGU Joint Meeting 2017, May 2017, Japanese, 幕張メッセ, International conference

  Poster presentation


• 捕獲された微惑星の周惑星円盤内での分布

  末次 竜, OHTSUKI KEIJI

  日本天文学会2017年春季年会, Mar. 2017, Japanese, Domestic conference

  Oral presentation


• 捕獲された固体物質の周惑星円盤内での分布

  末次 竜, OHTSUKI KEIJI

  日本惑星科学会2016年秋季講演会, Sep. 2016, Japanese, ノートルダム清心女子大学, Domestic conference

  Oral presentation


• 多様な巨大惑星リングの形成過程について

  兵頭 龍樹, Sebastien Charnoz, OHTSUKI KEIJI, 玄田英典

  日本惑星科学会2016年秋季講演会, Sep. 2016, Japanese, ノートルダム清心女子大学, Domestic conference

  Poster presentation


• 多様な巨大惑星リングの形成過程について

  兵頭 龍樹, Sebastien Charnoz, OHTSUKI KEIJI, 玄田英典

  日本惑星科学会2016秋季大会, Sep. 2016, Japanese, ノートルダム清心女子大学, Domestic conference

  Oral presentation


• Dynamical constraints on the mass of the largest body captured in Jupiter’s Trojan swarm

  Keiji Ohtsuki

  JUPITER TROJAN 2016, Jul. 2016, English, 宇宙科学研究所, International conference

  Oral presentation


• Migration of Small Solid Bodies in Circumplanetary Gas Disks

  Keiji Ohtsuki, Shumpei Shimizu, Hiroshi Kawamura, Ryo Suetsugu

  Goldschmidt2016, Jun. 2016, English, Pacifico Yokohama, International conference

  Poster presentation


• 周惑星ガス円盤中での微惑星軌道進化

  川村 浩司, OHTSUKI KEIJI, 末次 竜

  日本地球惑星科学連合2016年大会, May 2016, Japanese, 幕張メッセ, Domestic conference

  Poster presentation


• ガス抵抗による微惑星捕獲

  末次 竜, OHTSUKI KEIJI

  日本地球惑星科学連合2016年大会, May 2016, Japanese, 幕張メッセ, Domestic conference

  Poster presentation


• Orbital evolution of solid bodies in circumplanetary gas disks

  OHTSUKI KEIJI, 清水 俊平, 川村 浩司, 末次 竜

  日本地球惑星科学連合2016年大会, May 2016, English, 幕張メッセ, Domestic conference

  Oral presentation


• Capture of planetesimals by gas drag

  SUETSUGU Ryo, OHTSUKI Keiji

  Phobos, Deimos, and Mars Workshop, Feb. 2016, English, International conference

  Poster presentation


• ガス抵抗による微惑星の捕獲及び軌道進化

  SUETSUGU Ryo, OHTSUKI Keiji

  衝突研究会, Nov. 2015, Japanese, Domestic conference

  Poster presentation


• Physics of tidal disruption of big objects at the close encounter to Saturn

  HYODO Ryuki, Sebastien Charnoz, OHTSUKI Keiji, GENDA Hidenori

  47th DPS meeting, Nov. 2015, English, Domestic conference

  Poster presentation


• Gravitational Influence of a Large Captured Body on the Stability of Jupiter’s Trojan Asteroids

  OHTSUKI Keiji, OKAYAMA Hiroaki

  47th DPS meeting, Nov. 2015, English, International conference

  Poster presentation


• 捕獲された固体物質の周惑星円盤内での分布

  SUETSUGU Ryo, OHTSUKI Keiji

  日本惑星科学会秋季講演会, Oct. 2015, Japanese, Domestic conference

  Poster presentation


• 微惑星の土星近接遭遇による潮汐破壊：潮汐破壊過程の物理と土星リングの形成可能性

  HYODO Ryuki, Sebastien Charnoz, OHTSUKI Keiji, GENDA Hidenori

  日本惑星科学会秋季講演会, Oct. 2015, Japanese, Domestic conference

  Oral presentation


• 土星Fリング-羊飼い衛星系の起源：土星メインリング拡散による衛星-リング系の形成

  HYODO Ryuki, OHTSUKI Keiji

  日本惑星科学会秋季講演会, Oct. 2015, Japanese, Domestic conference

  Poster presentation


• ガス抵抗による微惑星の捕獲と軌道進化

  SUETSUGU Ryo, OHTSUKI Keiji

  日本惑星科学会秋季講演会, Oct. 2015, Japanese, Domestic conference

  Oral presentation


• 捕獲された固体物質の周惑星円盤内での分布

  SUETSUGU Ryo, OHTSUKI Keiji

  日本天文学会秋季講演会, Sep. 2015, Japanese, Domestic conference

  Oral presentation


• 周惑星円盤の散逸過程を考慮した微惑星の捕獲過程

  SUETSUGU Ryo, OHTSUKI Keiji

  日本天文学会秋季講演会, Sep. 2015, Japanese, Domestic conference

  Oral presentation


• ガス抵抗による微惑星の捕獲過程

  SUETSUGU Ryo, OHTSUKI Keiji

  衛星系研究会2015, Jul. 2015, Japanese, Domestic conference

  Poster presentation


• 捕獲されたトロヤ群小惑星の力学進化

  OHTSUKI KEIJI, 岡山 博明

  日本地球惑星科学連合2015年大会, May 2015, Japanese, Domestic conference

  Poster presentation


• Shapes and Dynamical Evolution of Aggregates Formed by Gravitational Accretion of Particles onto Embedded Moonlets in Saturn's Rings

  OHTSUKI KEIJI, Yasui Yuki

  46th Lunar and Planetary Science Conference, Mar. 2015, English, 米国テキサス州, International conference

  Poster presentation


• Distribution of captured planetesimals in circumplanetary disks

  SUETSUGU RYOU, OHTSUKI KEIJI

  46th Lunar and Planetary Science Conference, Mar. 2015, English, 米国テキサス州, International conference

  Poster presentation


• 惑星リングの拡散進化による衛星-リングの多様性

  Hyodo Ryuki, Ohtsuki Keiji

  新学術領域「系外惑星」B01,B02班研究会, Feb. 2015, Japanese, 東京工業大学, Domestic conference

  Oral presentation


• 捕獲された微惑星の周惑星円盤内での分布

  SUETSUGU RYOU, OHTSUKI KEIJI

  新学術領域「系外惑星」B01,B02班研究会, Feb. 2015, Japanese, Domestic conference

  Oral presentation


• On the diversity of satellite systems formed from Roche-interior particle disks

  Hyodo Ryuki, OHTSUKI KEIJI

  East Asian Young Astronomers Meeting 2015, Feb. 2015, English, 台湾, International conference

  Oral presentation


• 惑星リングの拡散進化と衛星集積

  Hyodo Ryuki, 大槻

  国立天文台CfCAユーザーズミーティング, Jan. 2015, Japanese, 国立天文台, Domestic conference

  Poster presentation


• Gravitational Accretion of Particles onto Moonlets in Saturn's Rings

  OHTSUKI KEIJI, Yasui Yuki, Daisaka Hiroshi

  46th DPS meeting, Nov. 2014, English, 米国アリゾナ州, International conference

  Poster presentation


• 捕獲された微惑星の周惑星円盤内での分布

  SUETSUGU RYOU, OHTSUKI KEIJI

  第１０回低温研衝突研究会, Oct. 2014, Japanese, 北海道大学低温科学研究所, Domestic conference

  Poster presentation


• 木星トロヤ群小惑星の軌道安定性について

  岡本 博明, OHTSUKI KEIJI

  日本惑星科学会2014年秋季講演会, Sep. 2014, Japanese, Domestic conference

  Poster presentation


• 捕獲された微惑星の周惑星円盤内での分布

  SUETSUGU RYOU, OHTSUKI KEIJI

  日本惑星科学会2014年秋季講演会, Sep. 2014, Japanese, 仙台市, Domestic conference

  Poster presentation


• 土星リング中での小粒子の重力集積による小衛星形成

  安井 佑貴, OHTSUKI KEIJI, 台坂 博

  日本惑星科学会2014年秋季講演会, Sep. 2014, Japanese, 東北大学片平キャンパス, Domestic conference

  Poster presentation


• 周惑星粒子円盤の進化と衛星系の多様性

  兵頭 龍樹, OHTSUKI KEIJI, 武田 隆顕

  日本惑星科学会2014年秋季講演会, Sep. 2014, Japanese, 東北大学片平キャンパス, Domestic conference

  Poster presentation


• 周惑星ガス円盤中での微惑星軌道進化と原始衛星への衝突確立

  清水 俊平, OHTSUKI KEIJI

  日本惑星科学会2014年秋季講演会, Sep. 2014, Japanese, 東北大学片平キャンパス, Domestic conference

  Oral presentation


• ラブルパイル小衛星の衝突破壊による土星Fリングの形成

  兵頭 龍樹, OHTSUKI KEIJI

  日本惑星科学会2014年秋季講演会, Sep. 2014, Japanese, 東北大学片平キャンパス, Domestic conference

  Oral presentation


• 周惑星粒子円盤の進化と衛星形成

  Hyodo Ryuki, OHTSUKI KEIJI, Takeda Takaaki

  衛星系形成研究会, Aug. 2014, Japanese, 北海道大学, Domestic conference

  Oral presentation


• Satellite formation from circumplanetary particle disks

  Hyodo Ryuki, OHTSUKI KEIJI, Takeda Takaaki

  Planetary Rings Workshop 2014, Aug. 2014, English, 米国コロラド州, International conference

  Oral presentation


• Gravitational Accretion of Particles onto Moonlets embedded in Saturn's Rings

  Yasui Yuki, OHTSUKI KEIJI, Daisaka Hiroshi

  Planetary Rings Workshop 2014, Aug. 2014, English, 米国コロラド州, International conference

  Oral presentation


• Collisions between gravitational aggregates in the tidal field

  Hyodo Ryuki, OHTSUKI KEIJI

  Planetary Rings Workshop 2014, Aug. 2014, English, 米国コロラド州, International conference

  Oral presentation


• Gravitational Accretion of Particles onto Moonlets in Saturn's Rings

  OHTSUKI KEIJI, Yasui Yuki, Daisaka Hiroshi

  AOGS 11th Annual Meeting, Jul. 2014, English, 札幌, International conference

  Oral presentation


• 来る10年の総括・将来ミッションの展望

  並木 則行, 小林 直樹, 出村 裕英, OHTSUKI KEIJI

  日本地球惑星科学連合2014年大会, Apr. 2014, Japanese, パシフィコ横浜, Domestic conference

  Oral presentation


• 反射スペクトルから見た木星小惑星の起源

  高遠 徳尚, 寺田 宏, 吉田 二美, OHTSUKI KEIJI

  日本地球惑星科学連合2014年大会, Apr. 2014, Japanese, パシフィコ横浜, Domestic conference

  Oral presentation


• 土星リング中の小衛星へのリング粒子の重力集積

  安井 祐貴, OHTSUKI KEIJI, 台坂 博

  日本地球惑星科学連合2014年大会, Apr. 2014, Japanese, パシフィコ横浜, Domestic conference

  Oral presentation


• 潮汐場におけるラブルパイル天体の衝突N体シュミレーション

  兵頭 龍樹, OHTSUKI KEIJI

  日本地球惑星科学連合2014年大会, Apr. 2014, Japanese, パシフィコ横浜, Domestic conference

  Poster presentation


• 土星リング中に存在する小衛星への重力による粒子集積

  安井 佑貴, OHTSUKI KEIJI

  ユーザーズミーティング CfCA-Center for Computational Astrophysics, Jan. 2014, Japanese, 国立天文台三鷹キャンパス, Domestic conference

  Poster presentation


• N体計算を用いた潮汐下におけるアグリゲイトの衝突破壊

  兵頭 龍樹, OHTSUKI KEIJI

  ユーザーズミーティング CfCA -Center for Computational Astrophysics, Jan. 2014, Japanese, 国立天文台三鷹キャンパス, Domestic conference

  Poster presentation


• Direct N-body Simulations of Aggregate Collisions in the Tidal Environment

  Ryuki Hyodo, OHTSUKI KEIJI

  Taiwan-Japan Symposium on Celestial Mechanics and N-Body Dynamics 2013, Dec. 2013, English, 台湾, International conference

  Oral presentation


• Capture of irregular satellites by gas drag from circumplanetary disk

  Ryo Suetsugu, Keiji Ohtsuki

  Taiwan-Japan Symposium on Celestial Mechanics and N-Body Dynamics 2013, Dec. 2013, English, 台湾, International conference

  Oral presentation


• Satellite formation from circumplanetary particle disks

  兵頭 龍樹, OHTSUKI KEIJI, 武田 隆顕

  日本惑星科学会2013年秋季講演会, Nov. 2013, Japanese, 石垣市民会館, 太陽系に存在する惑星の衛星系は、地球-月のような中心惑星に対して比較的大きな１つの衛星をもつ系(Single satellite system)と土星、天王星のように複数の衛星が存在する衛星系(Multiple satellites system)に大きく分類できる。 本研究ではN体計算を用いて初期にロッシュ半径の内側に形成された粒子円盤の進化の詳細を調べた。計算パラメーターとして中心惑星に対する初期の円盤質量を用いて、円盤進化とその結果形成される衛星系について議論する。, Domestic conference

  Oral presentation


• Collisional disruption of self-gravitating aggregates in the tidal environment

  兵頭 龍樹, OHTSUKI KEIJI

  日本惑星科学会2013年秋季講演会, Nov. 2013, Japanese, 石垣市民会館, 土星のFリングなどはロッシュ半径の外側ではあるが、中心惑星に比較的近い領域であるため中心惑星の潮汐力の効果が無視できない領域に位置している。一方、カッシーニによる観測結果からFリングにはリング粒子が自己重力で集積したアグリゲイトが多数存在していると示唆されている。さらに形成されたアグリゲイトは潮汐力で中心惑星方向に引き延ばされて、球体ではなく楕円体として存在していると考えられる。本研究では、楕円体のアグリゲイト同士の衝突を詳細に調べる事で、潮汐場での衝突破壊について議論する。, Domestic conference

  Poster presentation


• Orbital evolution of planetesimals by gas drag in circumplanetary disks

  清水 俊平, OHTSUKI KEIJI

  日本惑星科学会2013年秋季講演会, Nov. 2013, English, 石垣市民会館, 質量の十分大きな巨大惑星は、形成過程の後期で原始惑星系円盤から重力によりガスと固体を捕獲し、周惑星円盤を形成する。その円盤内で固体が集積し衛星系を形成したと考えられている。そのため、衛星形成を考える上で、円盤内のガス抵抗を考慮した微惑星の軌道進化は重要な研究対象である。そこで本研究では、軸対称円盤モデルを用いて、周惑星円盤内の微惑星軌道進化を調べた。, Domestic conference

  Poster presentation


• Capture of irregular satellites due to gas drag from circumplanetary disk

  末次 竜, 藤田 哲也, OHTSUKI KEIJI

  日本惑星科学会2013年秋季講演会, Nov. 2013, English, 石垣市民会館, 巨大惑星周りにある不規則衛星は、軌道の特長から捕獲された微惑星が起源だと考えられている。捕獲モデルの一つにガスによる捕獲モデルがあるが、捕獲後、惑星に落下してしまうという問題があった。これを避けるために、惑星に一時捕獲された微惑星が、何度も薄いガスと相 互作用することによって捕獲されるという捕獲モデルが提案された。しかしながら、捕獲の頻度などは明らかにされていなかった。そこで本研究では軌道計算を用いて、一時捕獲過程を考慮した不規則衛星の捕獲を詳しく調べた。, Domestic conference

  Poster presentation


• Dynamical evolution of Trojan asteroid

  岡山 博明, OHTSUKI KEIJI

  日本惑星科学会2013年秋季講演会, Nov. 2013, Japanese, 石垣市民会館, 木星のラグランジュ点L4,L5近傍にはトロヤ群と呼ばれる小惑星群が存在する。 トロヤ群の起源としてはガス抵抗による捕獲、木星の質量増加や軌道移動の効果による捕獲等が提案されてきたが、現在では「ニースモデル」を元にした微惑星の捕獲による説明が有力である。本研究では軌道進化の数値計算を用いて、トロヤ群小惑星の力学進化を調べたので、その結果について報告する。, Domestic conference

  Oral presentation


• Formation of multiple-satellite systems from circumplanetary particle disks

  Ryuki Hyodo, Keiji Ohtsuki, Takaaki Takeda

  45th DPS meeting, Oct. 2013, English, International conference

  Oral presentation


• Capture of irregular satellites due to gas drag from circumplanetary disk

  Suetsugu, Keiji Ohtsuki, Tetsuya Fujita

  45th DPS meeting, Oct. 2013, English, アメリカ合衆国コロラド州, International conference

  Oral presentation


• Temporary capture of planetesimals in the Kuiper belt

  Ryo Suetsugu, Keiji Ohtsuki

  2013 Pluto Scinece Conference, Jul. 2013, English, Johns Hopkins University, International conference

  Oral presentation


• Particle Accretion and Releasing Process around Moonlets in Saturn's Rings

  Yuki Yasui, Keiji Ohtsuki, Hiroshi Daisaka

  8th Workshop on Catastrophic Disruption in the Solar System, Jun. 2013, English, Hapuna Beach Prince Hotel, International conference

  Oral presentation


• Formation of Multiple Satellites from Circumplanetary Particle Disks

  Ryuki Hyodo, OHTSUKI KEIJI, Takaaki Takeda

  3rd Binary Workshop, Jun. 2013, English, アメリカ合衆国ハワイ州, International conference

  Oral presentation


• Capture of Irregular Satellites due to Gas Drag from Circumplanetary Disk

  Ryo Suetsugu, OHTSUKI KEIJI

  3rd Binary Workshop, Jun. 2013, English, アメリカ合衆国ハワイ州, International conference

  Oral presentation


• Aggregate Collision in the Tidal Environment

  Ryuki Hyodo, Keiji Ohtsuki

  8th Workshop on Catastrophic Disruption in the Solar System, Jun. 2013, English, Hapuna Beach Prince Hotel, International conference

  Oral presentation


• Local N-body simulation for Accretion of Particles onto Moonlets in Saturn's Rings

  安井 佑貴, OHTSUKI KEIJI, 台坂 博

  日本地球惑星科学連合2013年度連合大会, May 2013, Japanese, 幕張メッセ, Domestic conference

  Oral presentation


• Capture and orbital evolution of irregular satellites by gas drag from circumplanetary disk

  末次 竜, 藤田 哲也, OHTSUKI KEIJI

  日本地球惑星科学連合2013年大会, May 2013, Japanese, 幕張メッセ, Domestic conference

  Poster presentation


• Lunar and planetary explorations in a coming decade: Current status and ongoing schedule

  並木 則行, 小林 直樹, 出村 裕英, OHTSUKI KEIJI

  日本地球惑星科学連合2013年大会, May 2013, Japanese, 幕張メッセ, Domestic conference

  Poster presentation


• Evolution of circumplanetary particle disks and formation of multiple-satellite systems

  Hyodo, R, Ohtsuki, K, Takeda, T

  44ｔｈ Lunar and Planetary Science Conference，, Mar. 2013, English, 米国テキサス州, International conference

  Poster presentation


• Capture of Planetesimals by Circumplanetary Disks

  Yasui, Y, Ohtsuki, K, Daisaka, H

  44ｔｈ Lunar and Planetary Science Conference，, Mar. 2013, English, 米国テキサス州, International conference

  Poster presentation


• 周惑星円盤から受けるガス抵抗による微惑星捕獲

  FUJITA Tetsuya, OHTSUKI, Keiji

  日本惑星科学会2012年秋季講演会, Oct. 2012, Japanese, 日本惑星科学会, 神戸大学, Domestic conference

  Oral presentation


• 巨大惑星による微惑星一時捕獲過程

  SUETSUGU Ryo, OHTSUKI, Keiji

  日本惑星科学会2012年秋季講演会, Oct. 2012, Japanese, 日本惑星科学会, 神戸大学, Domestic conference

  Oral presentation


• Planet Mass Dependence of Rates and Source Region of Temporary Capture of Planetesimals by a Planet

  Suetsugu, R, Ohtsuki, K

  44th DPS meeting, Oct. 2012, English, 米国ネバダ州, International conference

  Poster presentation


• Capture of Planetesimals by Gas Drag from Circumplanetary Disks

  Fujita, T, Ohtsuki, K, Tanigawa, T

  44th DPS meeting, Oct. 2012, English, 米国ネバダ州, International conference

  Poster presentation


• Dependence of Temporary Capture on Planet's Mass

  Suetsugu, R, Ohtsuki, K

  Asia Oceania Geosciences Society 2012 Meeting, Aug. 2012, English, シンガポール, International conference

  Poster presentation


• 周惑星円盤による微惑星捕獲

  FUJITA Tetsuya, OHTSUKI, Keiji

  日本地球惑星科学連合2012年大会, May 2012, Japanese, 日本地球惑星科学連合, 幕張, Domestic conference

  Poster presentation


• 巨大惑星による微惑星一時捕獲過程

  SUETSUGU Ryo, OHTSUKI, Keiji

  日本地球惑星科学連合2012年大会, May 2012, Japanese, 日本地球惑星科学連合, 幕張, Domestic conference

  Poster presentation


• Temporary Capture of Planetesimals by a Giant Planet

  Suetsugu, R, Ohtsuki, K

  Asteroids, Comets, Meteors 2012, May 2012, English, 新潟, International conference

  Poster presentation


• Global Orbital Integration for Temporary Capture of Planetesimals by a Giant Planet: Implication for Their Source Region

  Suetsugu, R, Ohtsuki, K

  43rd Lunar and Planetary Science Conference, Mar. 2012, English, 米国テキサス州, International conference

  Poster presentation


• Capture of Planetesimals by Circumplanetary Disks

  Fujita, T, Ohtsuki, K, Tanigawa, T

  43rd Lunar and Planetary Science Conference，, Mar. 2012, English, 米国テキサス州, International conference

  Poster presentation


• Viscosity in Planetary Rings: Results From Numerical Simulations

  Yasui, Y, Ohtsuki, K, Daisaka, H

  EPSC-DPS Joint Meeting，, Oct. 2011, English, フランス・ナント, International conference

  Poster presentation


• Velocity Dispersion, Spin, and Viscosity in Planetary Rings，

  OHTSUKI KEIJI

  Workshop on Nonequilibrium Dynamics in Astrophysics and Material Science, Oct. 2011, English, 京都大学基礎物理学研究所, International conference

  Invited oral presentation


• Effects of Self-Gravity and Surface Friction of Particles on Viscosity in Planetary Rings

  Yasui, Y, Ohtsuki, K, Daisaka, H

  Workshop on Nonequilibrium Dynamics in Astrophysics and Material science，, Oct. 2011, English, 京都大学基礎物理学研究所, International conference

  Poster presentation


• Dynamical Behavior of Planetesimals Temporarily Captured by a Planet

  Suetsugu, R, Ohtsuki, K, Tanigawa, T

  EPSC-DPS Joint Meeting,, Oct. 2011, English, フランス・ナント, International conference

  Poster presentation


• Temporary Capture of Planetesimals by a Planet from Heliocentric Orbits

  Suetsugu, R, Ohtsuki, K, Tanigawa, T

  NCU-CPS 2011 Workshop on Planteary Dynamics，, Aug. 2011, English, 台湾・台湾中央大学, International conference

  Oral presentation


• Temporary Capture of Planetesimals by a Planet from Heliocentric Orbits

  Suetsugu, R, Ohtsuki, K, Tanigawa, T

  Asia Oceania Geosciences Society 2011 Meeting，, Aug. 2011, English, 台湾・台北, International conference

  Poster presentation


• Effects of Particles’ Spins and Surface Friction on Viscosity in Planetary Rings with Self-gravitating Particles

  Yasui, Y, Ohtsuki, K, Daisaka, H

  NCU-CPS 2011 Workshop on Planteary Dynamics，, Aug. 2011, English, 2011.8.15-16/台湾・台湾中央大学, International conference

  Oral presentation


• Effects of Particles’ Spins and Surface Friction on Viscosity in Planetary Rings with Self-gravitating Particles

  Yasui, Y, Ohtsuki, K, Daisaka, H

  Asia Oceania Geosciences Society 2011 Meeting，, Aug. 2011, English, 台湾・台北, International conference

  Oral presentation


• Asteroid Collision and Rotation，

  OHTSUKI KEIJI

  CPS-NCU Planetary Dynamics Workshop，, Aug. 2011, English, 台湾・台湾中央大学, International conference

  Invited oral presentation


• Viscosity in Planetary Rings with Spinning Self-Gravitating Particles Obtained by N-body Simulation

  Yasui, Y, Ohtsuki, K, Daisaka, H

  Workshop Rings 2011，, Jul. 2011, English, 米国ニューヨーク州、コーネル大, International conference

  Poster presentation


• Gravitational interactions among planets and planetesimals, and planetary formation

  OHTSUKI KEIJI

  Astronomical Summer Camp, Aug. 2010, English, 台湾, International conference

  Invited oral presentation

• Propellers and Wakes: A Predictive Study for Upcoming Close-Proximity Observations of Saturn's Rings

  Annabella Elizabeth MONDINO-LLERMANOS, 大槻圭史

  日本学術振興会, 外国人特別研究員, 神戸大学, Sep. 2026 - Aug. 2027, Others


• Applying solar system‑based ring physics to planetary debris evolution around white dwarfs

  Keiji Ohtsuki

  Japan Society for the Promotion of Science, Bilateral Collaborations, Kobe University, Apr. 2025 - Mar. 2027, Principal investigator


• 巨大惑星の衛星系形成における初期条件と材料物質混合過程の解明

  大槻 圭史, 末次 竜, 田中 秀和, 寺居 剛, 吉田 二美, 杉浦 圭祐

  日本学術振興会, 科学研究費助成事業, 基盤研究(B), 神戸大学, Apr. 2022 - Mar. 2025

  本研究の目的は、巨大惑星周囲のガス流からの抵抗を受けつつ周惑星円盤に降着する固体粒子の軌道数値計算により衛星材料物質の供給・輸送過程を明らかにすることである。今年度はまず、原始惑星系円盤から巨大惑星周囲に流れ込むガス流の解析を進め、周惑星円盤へのガス降着における諸量の惑星質量に対する依存性に着目して詳しく調べた。手法としては、我々が先行研究で用いたのと同様の流体シミュレーションコードを用い、惑星質量を幅広い範囲で変えてその依存性を明らかにした。その結果、ガス降着帯の動径方向の幅は惑星質量とともに増加すること、惑星質量依存性は惑星質量が小さい場合と大きい場合によって異なること等が明らかになった。本研究で得られたガス降着帯幅の結果をもとに、周惑星円盤へのガスの質量降着率の準解析解を導出した。この準解析式は今後の惑星形成モデルの構築において有用となり得る。以上の内容は査読付き論文として投稿、出版された。
  また、木星衛星系への材料物質供給とも関連して重要である木星トロヤ群小惑星の起源に制約を与えることを目的として、そのサイズ分布データ解析研究を実施した。手法として、すばる望遠鏡の超広視野カメラHyper Suprime-Camで取得された木星L5トロヤ群の微小小惑星のサイズ分布を解析し、同様の方法で得られていた木星L4トロヤ群の微小小惑星のサイズ分布と比較した。その結果、サイズ分布のべき指数は誤差の範囲で一致し、これらが共通のメカニズムを経て捕獲されたという理論モデルと矛盾しないことが明らかになった。これは、現在木星に向かっているNASAの木星トロヤ群小惑星探査機Lucyによる探査に備えて、重要な知見となる。以上の内容は査読付き論文として投稿、出版された。


• 巨大惑星近傍でのガスと固体粒子の相互作用

  大槻 圭史

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Kobe University, Apr. 2021 - Mar. 2023


• 計算機の中の惑星探査: 計算機の中の惑星リングの実現にむけて

  台坂 博

  科学研究費補助金, 基盤研究(C), Apr. 2018 - Mar. 2021

  Competitive research funding


• フラッシュX線を用いた衝突破壊の観測と小惑星サイズ頻度分布の衝突進化への応用

  荒川 政彦

  科学研究費補助金／基盤研究(B), Apr. 2016 - Mar. 2019

  Competitive research funding


• 太陽系における衛星系の特徴と多様性の起源の解明

  大槻 圭史

  科学研究費補助金／基盤研究(B), Apr. 2015 - Mar. 2019, Principal investigator

  Competitive research funding


• Tsunami early warning by realtime transfer of seafloor electromagnetic data

  Toh Hiroaki, IMAI Kazumasa, OHTSUKI Keiji, NAKAMICHI Akika, YAMAZAKI Akira, KAWASHIMA Issei, IWASHITA Kohdai

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Kyoto University, Apr. 2014 - Mar. 2017

  The tsunami is a dreadful natural disaster that can give enormous damage to human society. In this research, we conducted a geomagnetic study that leads to their prevention / mitigation. We aimed to apply to the existing tsunami early warning system the fact that observable electromagnetic fields are generated by coupling of tsunami particle motions of the conductive seawater with the Earth's main magnetic field. As a result, the following two were proved probable by both actual observation and three-dimensional numerical simulation: (1) real-time transfer of seafloor electromagnetic data for tsunami early warning purpose, (2) improvement of the existing tsunami early warning system by adding information from the tsunami-generated electromagnetic fields.


• 太陽系内氷小天体の起源と進化に関する理論研究

  大槻 圭史

  科学研究費補助金／基盤研究(B), Apr. 2010 - Mar. 2014, Principal investigator

  Competitive research funding


• Dynamical interactions between small bodies and giant planets

  OHTSUKI Keiji

  NASA, Origins of Solar Systems Program, 2008 - 2011, Principal investigator

  Competitive research funding


• Dynamics of spinning ring particles and stability of planetary rings

  OHTSUKI Keiji

  NASA, Outer Planets Research Program, 2008 - 2011, Principal investigator

  Competitive research funding


• Dynamical evolution of ring-satellite systems

  OHTSUKI Keiji

  NASA, Planetary Geology and Geophysics Program, 2008 - 2011, Principal investigator

  Competitive research funding


• Dynamical interactions between small bodies and gas giant planets

  OHTSUKI Keiji

  NASA, Origins of Solar Systems Program, 2005 - 2008, Principal investigator

  Competitive research funding


• Rotation of moonlets and particles in planetary rings around giant planets

  OHTSUKI Keiji

  NASA, Outer Planets Research Program, 2005 - 2008, Principal investigator

  Competitive research funding


• Dynamical evolution of ring-satellite systems

  OHTSUKI Keiji

  NASA, Planetary Geology and Geophysics Program, 2005 - 2008, Principal investigator

  Competitive research funding


• Collisional and rotational evolution of small asteroids

  OHTSUKI Keiji

  NASA, Discovery Data Analysis Program, 2004 - 2007, Principal investigator

  Competitive research funding


• Formation and dynamical evolution of planets

  OHTSUKI Keiji

  NASA, Origins of Solar Systems Program, 2003 - 2007, Principal investigator

  Competitive research funding


• Origin and evolution of irregular satellites

  OHTSUKI Keiji

  NASA, Origins of Solar Systems Program, 2002 - 2005, Principal investigator

  Competitive research funding


• Dynamical evolution of ring-satellite systems

  OHTSUKI Keiji

  NASA, Planetary Geology and Geophysics Program, 2002 - 2004, Principal investigator

  Competitive research funding


• The origin of diversity of extrasolar planets formation of giant gasous planets and orbital evolution

  NAKAZAWA Kiyoshi, EMORI Hiroyuki, WATANABE Seiichiro, IDA Shigeru

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Tokyo Institute of Technology, 1997 - 1999

  About 30 extrasolar planets have been discovered since 1995. They would be giant planets like Jupiter and Saturn in the Solar system, because the present detection method limits planet mass that can be detectable. About half of them have very short orbital period (shorter than that of Mercury), while the other half have large orbital eccentricity. We have tried to explain the diversity of the extrasolar planets by generalizing the standard theory of the Solar system. This year, we investigated the formation of giant planets and their orbital stability more deeply. Giant planets are formed as follows a solid core with about 10 earth masses accretes from planetesimals and gas of a protoplanetary disk is captured by strong gravity of the core to form massive envelope. We investigated (1) the dependence of formation of a solid core on mass of a protoplanetary disk, (2) time scale of gas infall onto the core, and (3) orbital stability of giant planets in the protoplanetary disk. Regarding (1), we found that in a massive protoplanetary disk, gas giant planets can be formed in inner region. Regarding (2), we found that gas infall can start at less massive core mass than so far considered, but the time scale of gas infall is rather long. Regarding (3), we found that gas drag generally stabilizes the orbits, but the effect is weak if separation distance between the planets is smaller than some critical value. From these results, we conclude that generalization of the standard theory of the Soalr system to different mass protoplanetary disks would account for the diversity of the extrasolar planets.


• Planetary Formation relevant to Titius-Bode's Law

  NAKAZAWA Kiyoshi, OHTSUKI Keiji, EMORI Hiroyuki, IDA Shigeru

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), TOKYO INSTITUTE OF TECHNOLOGY, 1995 - 1997

  In the last decade great efforts have been dedicated to solve two big problems in studies for planetary formation processes. One problem is that we could not explain the formation of Jovian planets. such as Jupiter and Saturn in the proto solar nebula which is considered to dissipate in a very little time as equal as about ten million years. And another is that we could not explain present distances between planets. Until now a sequence of the planetary formation that terrestrial planets orbiting near the Sun accumulated faster than the Jovian planets in the distant orbit from the Sun has been accepted. To consider the two big problems we abandoned this preconception and adopt a new working hypothesis that the Jovian planets are formed before the terrestrial planets are accumulated. We consider that strong gravity from the Jovian planets are necessary to reproduce present arrange of the terrestrial planets. At first, to adopt the working hypothesis it is necessary to consider the formation process of the Jovian planets. To produce a Jovian planet which has great amount of hydrogen gas a solid core should accumulate in the proto solar nebula and become large enough to attract gas from nebula by it's gravity. The minimum mass of the solid core to attract gas from solar nebula was believed to be about 10 times earth's mass. It is very difficult to produce such large solid core in the present Jupiter region within ten million years. We studied the accumulation process of a solid ore and the gas capturing process by the core. Summarizing the result we conclude as follows. (1) It is possible to produce a solid core with few tines earth's mass at present Jupiter's orbit in ten million years. (2) Owing to the decline of the planetesimal accumulation rate to the solid core in the last stage of it's growth a solid core with only few times earth's mass can attract gas from the proto solar nebula. From thses results we conclude that jovian planets are possibily accumulated before present terrestrial planets are formed. So, the necessity to investigate the late stage accumulation of the terrestrial plates under the effect of strong gravity from the Jovian planets increases.


• 微惑星衝突による地球-月系の角運動量および小惑星自転の研究

  大槻 圭史

  科学研究費補助金, 奨励研究(A), 奨励研究(A), 山形大学, Mar. 1995 - Apr. 1996, Principal investigator

  本研究では、原始惑星から受ける重力作用によってまわりの微惑星の空間分布が非一様になった状況のもとで、惑星がこれらの微惑星を集積することによって獲得し得る自転角運動量について調べた。 微惑星集団の離心率と軌道面傾斜角は、それぞれ独立にレイリー分布と呼ばれる分布を持つことが知られている。そこで、与えられた分散値をもつレイリー分布になるような40組の離心率および軌道面傾斜角を選び、それぞれの組について、100万から1000万の軌道を数値計算することにより、惑星に衝突する軌道を見つけ、惑星に与える角運動量を求めた。これら40組の結果をもとに、様々な非一様分布が惑星の周りに形成された場合について、惑星が獲得する自転角運動量を求めた。上のような計算を、離心率と軌道面傾斜角の分散値を何通りか変えて行った結果、次のことが明らかになった。 1.非一様分布を考慮すると、一様であると仮定した場合に比べて、惑星が獲得する自転角運動量は10倍以上になりうる。 2.しかし、現実的な分布を考える限り、高速自転不安定により月を分裂させるのに必要なほど大きな角運動量を原始地球に与えるのは不可能である。従って「月は原始地球からの分裂によって形成された」という説は、誤りである。 3.また、現在の地球-月系の角運動量に相当する値を原始地球に与えるためには、微惑星の分布がかなり片寄った特別な分布になる必要がある。そのような分布が形成される可能性について、今後、詳しく調べる必要がある。 4.さらに、同様の非一様分布を考慮することによって、火星の自転は説明できる。また、金星領域で原始太陽系星雲ガスが比較的早い段階で消失したと仮定すれば、金星の逆行自転も説明できる可能性がある。これらについても、さらに詳しい検討が必要である。

  Competitive research funding


• Gas capture by distant protoplanets and the formation of Jovian planets.

  NAKAZAWA Kiyoshi, IDA Shigeru, OHTSUKI Keiji

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for General Scientific Research (C), Tokyo Institute of Technology, 1993 - 1994

  To clarigy the formation processes of Jovian planets and the origin of their characters, we investigated (i) the static structure of the gas envelope covering a protoplanet and (ii) the collapse process of the unstable gas envelope and developed the simulation code describing (iii) the capture of the nebular gas by a protoplanet. Our main results are summarized as follows. (i) Static structure of the gas envolope covering a protoplanet The structure of the gas envelope is mainly governed by the energy released in the envelope due to the accretion of planetesimals. Taking into account fragmention of incident planetesimals due to the dynamical pressure, we estimated the energy flux and obtained the static solution of the gas envelope. As a result, we showed that fragmentation of planetesimals fairly reduces the energy flux and the critical core mass and that the critical mass we obtained becomes 1/4 of the value obtained by the previous studies. (ii) The collapse process of the unstable gas envelope Next, we performed simulations of the collapse of the unstable gas envelope, taking into account the infall of the nebular gas. Futhermore, we analized the dynamical instability of the collapsing gas. Then we showed that the oscillational instability and the mass ejection suggested by Wuchterl (1993) do not occur. Our results support the formation process proposed in Kyoto model. (iii) Capture of the nebular gas by a protoplanet Using the results in (i) and (ii), we started the development of the new simulation code describing the capture of the nebular gas by a protoplanet. The previous study had a demerit that the way of the gas capture strongly depends on the algorism of the code. We are now developing the new code which can overcome the demerit.


• 太陽重力を考慮した惑星集積過程と原始太陽系星雲の進化

  大槻 圭史

  科学研究費補助金, 奨励研究(特別研究員), 奨励研究(特別研究員), 東京大学, Apr. 1990 - Mar. 1992, Principal investigator

  Competitive research funding