1. The Crab Nebula is the result of a that was witnessed on Earth in the year 1054. 2. Betelgeuse is a supergiant star that will eventually supernova, which means that by mass it is classified as a . 3. The debris from the death of a high-mass star forms a several light years across. 4. A has a density higher than the density of a white dwarf. 5. actually occurred about 150,000 years ago in the Large Magellanic Cloud. 6. The is the process by which hydrogen fusion proceeds in high-mass stars. 7. Carbon can be converted into oxygen in the cores of high-mass stars if carbon nuclei undergo a .