The 1995 Laureates / Basic Sciences Category / Earth and Planetary Sciences, Astronomy and Astrophysics

Astrophysics and I - Motives, Methods, and the Outline of My Research - 

Theoretical research in astrophysics has been a major part of my life. On this occasion, I would like to recall my past days and talk about what made me choose astrophysics as my field of study, what research subjects I selected, what method I used in my researches, and what results I obtained.

My research method has been consistent: I applied fundamental physical laws to clarifying evolutionary processes of the universe and various heavenly bodies. There are two types of fundamental physical laws: "micro-laws", such as the laws of quantum mechanics and statistical mechanics; and "macro-laws", such as Newton's theory of gravity and the general theory of relativity. Evolutionary processes occurring within a heavenly body (microprocesses) and those in the entire body (macroprocesses) influence each other tremendously. To explore stellar evolutionary processes, I pursued changes over time in both macro and microprocesses.

My research themes can be roughly classified into the following three: the synthesis of elements in the early phase of the Big Bang universe; the internal structure of red giant stars, as well as stellar evolution induced by nuclear fusion; and the origin of the solar system, namely, how earth and other planets were born. Regarding these three themes, I will briefly explain researches conducted prior to my own, and then my own research results.

I will begin my presentation with this question: in element synthesis processes during the early phase of the universe, what quantity of protons and neutrons combined to form helium, and what quantity of protons remained in the form of hydrogen. (During the initial high-temperature period of the universe, there were protons and neutrons.) Next, I will describe the structure of red giant stars. Their temperature and density distributions differ greatly from those of the sun. Then, I would like to proceed to two topics of stellar evolution. One is the evolutionary stages at which heavy elements were synthesized sequentially in the cores of stars, and the other is the evolution of primordial stars prior to the commencement of nuclear fusion reactions. Finally, I would like to outline the formation of the solar system. This process comprises multiple stages. In the primordial solar nebula, the separation of dust from gas first occurred. The dust then accreted to form many planetesimals. Some of these planetesimals accreted further, growing into solid planets.