Origin and occurrence of fluorine supernovae, atoms of neon could be hit by neutrinos during the explosion and converted to fluorine. In Wolf-Rayet stars (blue stars over 40 times heavier than the Sun), a strong solar wind could blow the fluorine out of the star before hydrogen or helium could destroy it. Finally, in asymptotic giant branch (a type of red giant) stars, fusion reactions occur in pulses and convection could lift fluorine out of the inner star. Only the red giant hypothesis has supporting evidence from observations. In space, fluorine commonly combines with hydrogen to form hydrogen fluoride. (This compound has been suggested as
Red giant system, if present, uninhabitable, some research suggests that, during the evolution of a star along the red-giant branch, it could harbor a habitable zone for several times 10 years at 2 AU out to around 10 years at 9 AU out, giving perhaps enough time for life to develop on a suitable world. After the red-giant stage, there would for such a star be a habitable zone between 7 and 22 AU for an additional 10 years. Later studies have refined this scenario, showing how for a star the habitable zone lasts from 10 years for a planet with an