(CNN)Astronomers have discovered a new type of supernova, or star explosion, and it provides a new window into the violent life cycle of stars. The new research, focused on supernova 2018zd, confirms a prediction made by University of Tokyo astronomer Ken'ichi Nomoto more than 40 years ago.... ...Typically, supernovae occur in two flavors. During a core-collapse supernova, a massive star (more than 10 times the mass of our sun) exhausts its fuel and the star's core caves in to a black hole or a dense remnant called a neutron star. The other type is called a thermonuclear supernova, and it...