Hydrogen-deficient star the outer layer of the star. The double degenerate scenario is a binary-star approach in which a smaller degenerate helium white dwarf and a larger carbon-oxygen white dwarf orbit each other so closely that they eventually inspiral due to gravitational wave losses. At the Roche limit, mass transfer takes place from the helium to the carbon-oxygen star. The latter undergoes helium shell burning to form a supergiant and evolve to a hydrogen-deficient star. The double degenerate scenario provides a better fit to the observational data. Hydrogen-deficient star A hydrogen-deficient star is a type of star that has little or no
Red giant stars develop into supergiants that follow an evolutionary track that takes them back and forth horizontally over the HR diagram, at the right end constituting red supergiants. These usually end their life as a type II supernova. The most massive stars can become Wolf–Rayet stars without becoming giants or supergiants at all. Red giants with known planets: the M-type HD 208527, HD 220074 and, as of February 2014, a few tens of known K-giants including Pollux, Gamma Cephei and Iota Draconis. Although traditionally it has been suggested the evolution of a star into a red giant will render its planetary