This book presents the discovery or explanation of three new classes of supernovae utilizing data from the Global Supernova Project which brings together new wide-field and high-cadence transient surveys that enable the astrophysics community to watch supernovae from the moment of explosion. Firstly, electron-capture supernovae are a class of supernovae theorized for 40 years, whose discovery detailed within bridges the gap between massive star explosions and the fate of stars with the mass of the Sun. This has implications for stellar astrophysics, gravitational-wave events, and cosmic nucleosynthesis. The second major insight concerns short-plateau supernovae, supernovae that remain at a nearly constant brightness for approximately 2 months, in contravention to nearly all other similar supernovae. The author’s light-curve model grid places them in a rare transitional class near high mass supergiant progenitors, where direct collapse to black holes may be expected. Thirdly, superlinear superluminous supernovae are much brighter than previously thought possible and show an unusual linear decline in brightness, only a few examples of which have been found. The author’s models suggest the supernova explosion is sweeping up material lost from the progenitor star and its stellar companion in the last few years of its life. The new discoveries and insights presented within have major implications for many areas of astrophysics and physics in general.

Daichi Hiramatsu is originally from Tokyo, Japan, and started his academic journey in the United States after high school. He earned his B.S. in physics and minor in astrophysics from the University of Hawaii at Manoa in 2016 and his M.A. and Ph.D. in physics with astrophysics emphasis from the University of California, Santa Barbara, in 2019 and 2021, respectively, where he worked with Prof. Andy Howell on supernovae and gravitational-wave events using the global telescope network of Las Cumbres Observatory. He was then a postdoctoral research fellow at the Center for Astrophysics | Harvard & Smithsonian before joining the University of Florida as an assistant professor in 2025. 

Hiramatsu is mainly interested in how massive stars die as explosive transients called supernovae. He uses both observations and simulations of supernovae to extract their progenitor and explosion properties from the time series of photometry and spectroscopy.