An astrophysicist who introduced the knowledge and methods of fundamental physics into analysis of astronomical phenomena, applying scientific principles from such fields as nuclear physics and fluid dynamics. Through studies of stellar evolution and the solar system, he developed theories explaining many astronomical phenomena and contributed immeasurably to the maturation of modern astrophysics.
Proton-Neutron Concentration Ratio in the Expanding Universe at the Stages Preceding the Formation of the Elements. Prog. Theor. Phys., 5.
Stellar Evolution in Early Phases of Gravitational Contraction. Publ. Astron. Soc. Japan, 13.
Evolution of the Stars (with R. Hoshi and D. Sugimoto). Prog. Theor. Phys. Suppl., 22.
Growth of Solid Particles in the Primordial Solar Nebula (with T. Kusaka and T. Nakano). Prog. Theor. Phys., 44.
Formation of the Planets (with I. Adachi and K. Nakazawa). Prog. Theor. Phys., 55.
Formation of the Solar System (with K. Nakazawa and Y. Nakagawa). Protostars and Planets II, (Univ. Arizona Press)
By introducing the knowledge and techniques of the broad area of basic physical sciences of atomic nuclei and hydrodynamics to the analysis of the universe, Dr. Chushiro Hayashi has opened a new phase in research into the evolution of stars and the origins of solar systems with his theoretical explanation of various phenomena of celestial bodies, and has ultimately made an enormous contribution to the development of modern astronomical physics.
Astronomical physics is the science of studying and analyzing those heavenly bodies, such as planets and stars, with which we are so familiar. The evolutionary time schedule of celestial phenomena, however, is extremely long, and observations that are made can be considered merely as snap shots of the various evolutionary stages of the universe and its components. Dr. Hayashi has taken these countless “snap shots” and theoretically analyzed them under the light of basic physics to determine their sequence and construct a consistent, theoretical model for the formation of the stars and their evolutionary processes. His achievements in the field have received the very highest acclaim from all over the world.
Dr. Hayashi has been involved in the general analysis of the evolutionary processes of the stars since the 1950’s, and is recognized for numerous innovative achievements related to theories of star formation. In the area of stellar evolution theory, Dr. Hayashi has, based on his theories concerning the internal structure of stars and atomic nuclear reactions, succeeded in explaining the composition and development of heavenly bodies such as main-sequence stars, giant stars and white dwarfs. In particular, his paper entitled “Evolution of the Stars,” which was published in 1962, has long been considered the leading authority and reference for astronomical researchers working on the evolution of fixed stars, and it would not be an exaggeration to say that the theories developed through his research have completely explained the main points of the field. In the area of stellar formation theory, he discovered a period of stellar development which occurs during the birth of star; a period of extreme activity when the brightness of the star reaches a luminosity-several tens of times brighter than even that of a main-sequence star. This phase, when a star is in the process of being born, has been termed the “Hayashi Phase,” the first and only time a concept in the science of astronomy has been crowned with a Japanese name.
In the field of solar system formation theory as well, Dr. Hayashi has theoretically analyzed how the planetary systems and fixed stars of solar systems such as our own are born. With his model for the origin of solar systems, known as the “Kyoto Model,” he has made important contributions in the area defined by astronomy and earth planet sciences. Recently, with the rapid progress of radio wave, optical and infrared telescopes and detection equipment, observations in the area of planetary system formation in solar systems other than our own have become possible, and among the resulting deluge of new data and information have been numerous finds which have further verified the model that Dr. Hayashi originally constructed.
The achievements that Dr. Hayashi has realized through his research and investigations have fundamentally brought about a new, standardized level of knowledge and understanding to astronomical physics. The consistent theories that he has successfully developed concerning the stars and planets have established him as a giant in the field of physical astronomy, and a representative of this century. Also widely acclaimed for his influence and guidance of numerous bright young researchers in the field, Dr. Chushiro Hayashi is truly worthy of the 1995 Kyoto Prize for Basic Sciences.
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.