When the core of a massive star runs out of nuclear fuel, it collapses under its own gravity to form a neutron star or a black hole and sheds its outer layers in a supernova. (See, for example, the article by Hans Bethe, Physics Today, September 1990, page 24.) However, for smaller stars in the 7- to 11-solar-mass range, gravitational collapse may not be the only possible route to a supernova. Those stars are abundant in our galaxy, but the final phase of their evolution is unclear. Some may undergo gravitational collapse like massive stars. But if nuclear reactions in a star’s core generate sufficient energy to counter collapse, its life may also end in a thermonuclear explosion that ejects some material while leaving behind a white dwarf remnant.
To understand the fate of a star, astrophysicists must delineate the nuclear reactions that occur in its core after...
