Introduction of Space and Planetary Science Group
Our research fields are space physics, and planetary science for both solar-system bodies and exoplanets. We conduct research using various methods including precise analysis of extra-terrestrial materials such as meteorites, in situ measurements as well as remote-sensing observations from spacecraft, theoretical and numerical approaches, and laboratory experiments. In particular, we have close collaboration with JAXA for the development of scientific instruments, data analysis for spacecraft observations of the solar atmosphere, earth’s magnetosphere, and planetary exploration.
More than 99% of dilute, high-temperature gasses in space are in an ionized state called a plasma. Understanding of plasma physics is, therefore, critical in various aspects of astrophysical phenomena. We consider the solar system as “a plasma physics laboratory in space,” and conduct research on, e.g., shock waves producing high-energy particles, magnetic reconnection leading to explosive phenomena such as solar flares and aurora breakups. We apply the understanding of these elementary plasma physics obtained with the solar system plasma research to more general astrophysical phenomena. We also conduct fundamental physics research such as nonlinear physics and non-equilibrium physics which often become important in space and astrophysical plasmas.
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Solar-Planetary System Science
Planets in the solar system, including the Earth on which we live, are constantly influenced by the sun and the outer space surrounding the planets. From the sun, the solar radiation and plasma flows called as the solar wind are continuously emitted, and the latter significantly varies with the solar activity. In our research group, we investigate the sunspot variation, solar flares, and coronal heating problems, which are the energy sources of the solar-planetary system, by making full use of a large-scale simulation using supercomputers. We combine numerical simulations with satellite and ground-based observations in order to understand underlying physics in the space weather phenomena such as the aurora, radiation belt variations, and the geospace storms.
Planets have different characteristics in various aspects, such as distance from the sun, size, intrinsic magnetic field, and atmosphere. Although the solar-planetary system is a complex system in which these interact intricately, studies of other planets with different conditions give us important insights on understand the influence of specific elements. For example, by studying Mars and Venus which do not have a strong global intrinsic magnetic field like the Earth, we can clarify the influence of the intrinsic magnetic field of the planet on the variation of the solar-planetary system and evolution of the planetary surface environment. In our research group, we conduct our studies in close collaboration with related satellite missions such as Hinode (solar observation), Hisaki (planetary telescope), MAVEN (Mars), and BepiColombo (Mercury).
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Planetary Material Science
We have obtained various kinds of extraterrestrial materials. They include meteorites, lunar samples, cosmic dust, and returned samples such as Itokawa asteroidal dust and Wild 2 cometary particles. Their sizes span wide ranges, but we are applying micro-area analytical techniques for petrological, mineralogical and isotopic studies to understand when our solar system formed and how it has evolved into the present form.
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The ultimate goal of the “comparative planetology” is to answer the question of what the Earth is like today (full of water and life!), and why we are there. It is obvious that knowing the history of the earth’s evolution is very important for us human beings. However, if we are looking only at the Earth, it will not lead to a deep understanding of the Earth. You may know that the studying about foreign countries is very effective in order to understand your own country. Therefore, knowing how and why a nearby planet in the solar system is different from the earth is important to understand the Earth. For such purposes, we are conducting researches using various approaches such as Exploration, Observation, and Laboratory experiments” with the theme of Planets, Satellites, Comets, Small celestial bodies, and Meteorite impact”.
Space and Planetary Exploration
Space and planetary exploration projects typically take 10-20 years from the beginning of brainstorming on scientific targets to the start of observation. This is due to the need for long-term development and verification of huge systems of spacecraft. In contrast, we are opening a new door for innovative, agile explorations with compact but essential spacecraft by concise teams in the university. The short-term cycle enables that students are involved through a whole project, from the design of mission concepts to the launch and data analyses. The mission goal can be determined from the broad spectrum in our department, e.g., solar and planetary evolutions, and the formation of high-energy astrophysical objects. As a natural consequence for the implementation of these projects, we deeply collaborate with department of engineering, graduate school of frontier sciences, and Japan aerospace exploration agency.
Related website：UTokyo Organization for Planetary and Space Science (UTOPS)