Professor of High-Energy Astrophysics

Shuichi Gunji

▲Image of gamma-ray bursts (provided by Professor Daisuke Yonetoku of Kanazawa University).

Gamma ray bursts: The largest cosmic explosion

A variety of high-energy phenomena occur in outer space. Among these, gamma-ray bursts are said to be the largest cosmic explosions. Gamma-ray bursts are so strong that the total energy emitted by our Sun during its entire lifespan is emitted in a single explosion lasting only several dozen seconds. From the Earth, a large amount of gamma-rays have been observed to fall from a certain direction at intervals of several dozen seconds.

▲Instruments for measuring gamma rays are under development.

A mysterious emission mechanism

Two main types of gamma-ray bursts are thought to exist. The first type occurs simultaneously with the massive supernova explosion of a star which possesses a mass that is several tens of times greater than our Sun. The second type occurs during the merger of a binary star belonging to an ultra high-density celestial body such as a black hole or a neutron star. Although approximately 50 years have passed since gamma-ray bursts were discovered, mechanism in which a large volume of gamma-ray bursts are emitted is still a mystery. However, by measuring the polarization of gamma rays falling onto the Earth, scientists hope to clarify the emission mechanism of gamma rays.

▲We aim to mount detectors on the International Space Station.

Developing high-precision detectors to solve the mystery

Currently, there are no high-precision detectors capable of measuring gamma ray polarization. In response, Yamagata University is cooperating with NASA and the University of New Hampshire in order to develop such detectors. We are conducting development with the aim of mounting these detectors on the International Space Station in 2022. Our ultimate goal is to solve the mystery of gamma-ray bursts.