Research

研究室メンバーの書いた日本語解説記事はこちら

Planetesimals (微惑星) are kilometer-sized solid bodies that form planets. They form from dust (塵) in protoplanetary disks. 

Key questions:

• How do µm-sized dust grains stick together? 

• Do planetesimals form only in special locations in the disks? 

• Do rocky and icy planetesimal form in different ways?

Our recent work: 

• Understanding the isotopic dichotomy (同位体二分性) in the solar system using dust size evolution simulations (Homma et al. 2024)

• Disks around massive protostars (大質量原始星) as a laboratory for studying the growth of rocky grains (Yamamuro et al. 2023)   

• Local planetesimal formation at the border of the "dead zone" (Ueda et al. 2021)

• Sticking of grains coated by organics (有機物) (Homma et al. 2019)

関連する日本語解説:  荒川・深井・本間 (2022)  奥住 (2016)  

In protoplanetary disks, water ice is present outside the orbit where the temperature reaches about 160 K. This orbit is called the snow line (スノーライン). Its location is key to understanding how water is delivered to planets. 

Key questions: 

• Where is the snow line? 

• How did its location affect the origin of our Earth? 

• Can we observe the snow line using telescopes?

Our recent work: 

• Temperature evolution of protoplanetary disks with shadows (Okuzumi et al. 2022)

• Finding the snow line using near-future radio telescopes (Okuzumi et al. 2021)

• Snow line evolution predicted from magnetohydrodynamics (磁気流体力学)  (Mori et al. 2021; Kondo et al. 2023)

• Water delivery to planets in disks (Sato et al. 2016) 

関連する日本語解説:  森 (2021)  奥住 (2019)  

NHK コズミックフロント「海の起源をめぐるミステリー」 (奥住出演, 2021)

Understanding the structure, dynamics, and evolution of protoplanetary disks is essential for studying planet formation and for correctly interpreting disk observations. 

Key questions: 

• Are protoplanetary disks turbulent (乱流的)? 

• How do the disks interact with dust and planets? 

• What are the roles of magnetic fields (磁場) in disk evolution? 

Our recent work: 

• Disk heating by planets (Okamura et al., in prep.)

• Transport of magnetic fields in disks (Enomoto et al., in prep.)

• Coevolution of dust and turbulence (Fukuhara et al. 2021, 2023; Fukuhara & Okuzumi 2024)

• Disk heating in magnetohydrodynamic simulations (Mori et al. 2019)

関連する日本語解説:  森 (2021)  奥住(2016)

The composition of small exoplanets is poorly constrained. We do not know the mass and density of many exoplanets discovered by transit observations. Many small exoplanets are also covered by thick clouds (雲) and haze (もや), which prevent us from knowing what their atmospheres are made of. 

Key questions:

• Are Earth-sized exoplanets rocky? Or are they water worlds (海洋惑星) entirely covered by a thick ocean and high-pressure ice?

• Why are small exoplanets so cloudy? What does that tell us about the planets' composition?  

Our recent work: 

• Microphysical modeling of mineral clouds (鉱物雲) on small exoplanets (Ohno & Okuzumi 2017, 2018; Ohno et al. 2020)

• Knowing the composition of "disintegrating" exoplanets (解体惑星) with JWST and other future telescopes (Okuya et al. 2020)

関連する日本語解説:  大野 (2020)