Among stellar objects in the universe, massive stars (more than roughly 8 solar masses) are thought to explode as supernovae at the endpoint of their lives. Supernova explosions primarily contain information on the properties of the explosion itself, as well as the characteristics of the evolution of the progenitor. Understanding those features allow us to reveal how massive stars have lived and how they have died.

Since massive stars release enormous energy (~10^44 Joule = 10^51 erg) in an instant through supernova explosions, a variety of electromagnetic signals can be observed. The most drastic features from supernovae are often seen in the optical wavelength (~400-800 nanometer), both through photometry and spectroscopy. These experiments enable us to answer the following questions; how massive the progenitor was, how energetic the explosion was, what kind of elements the progenitor consisted, and how rapidly the ejected gas is moving... etc. 

Sometimes, radio, X-rays, and even in some cases, gamma-rays can be detected from supernovae. These signals are considered to be originated from relativistically accelerated particles, contrary to the case of optical emission. One of the strengths of utilizing these wavelength is that we can robustly trace the nature of the circumstellar material around the supernova progenitor. Thus it becomes possible for us to speculate the final evolution of massive stars from the perspective of mass-loss activities of massive stars. Another point is that they can provide us with clues for understanding the nature of high-energy particle physics; these signals have potential to probe the nature of high-energy astrophysical phenomena related to particle acceleration and magnetic field amplification.

Long after the supernova explosion, the ejecta continues to expand into the circumstellar/interstellar space, and the system evolves into a spreaded system called a supernova remnant. Since most of the observed supernova remnants inhabit our galaxy, we can see beautiful pictures of supernova remnants taken by some instruments. While optical emissions from supernova remnants are inconspicuous, non-thermal emissions in the wavelength range of radio, X-ray, and gamma-ray become powerful. Therefore the processes of particle acceleration, diffusion, and non-thermal radiation can be intensively investigated through the study of supernova remnants. Furthermore, recently there are some attempts to connect the understanding between the evolution of massive stars and supernova remnants, leading to the construction of the sophisticated stellar evolution theory.