core-collapse supernova

The core collapse of sufficiently massive stars may not be halted. Degeneracy pressure and repulsive neutron-neutron interactions can only support a neutron star whose mass does not exceed the Tolman-Oppenheimer-Volkoff limit of very roughly 4 solar masses. Above this limit, the core collapses to directly form a black hole, perhaps producing a (still theoretical) hypernova explosion. In the proposed hypernova mechanism (known as a collapsar) two extremely energetic jets of plasma are emitted from the star's rotational poles at nearly light speed. These jets emit intense gamma rays, and are one of many candidate explanations for gamma ray bursts.

Crab Nebula

A significant problem in studies of the Crab Nebula is that the combined mass of the nebula and the pulsar add up to considerably less than the predicted mass of the progenitor star, and the question of where the 'missing mass' is remains unresolved.

Soyuz.

About five percent of the people that have been launched have died doing so (because astronauts often launch more than once). As of November 2004, 439 individuals have flown on spaceflights: Russia/Soviet Union (96), USA (277), others (66). Twenty-two have died while in a spacecraft: three on Apollo 1, one on Soyuz 1, one on X-15-3, three on Soyuz 11, seven on Challenger, and seven on Columbia. By space program, 18 NASA astronauts (4.1%) and four Russian cosmonauts (0.9% of all the people launched) died while in a spacecraft.