Final answer:
In low-mass stars, the helium flash indicates a transition from a red giant stage to a white dwarf. This process involves the fusion of helium into carbon, and after the helium is exhausted, the core stops fusion and the outer layers are ejected, becoming planetary nebulae.
Step-by-step explanation:
In low-mass stars, the helium flash leads to the transition from a red giant to a white dwarf. The helium flash is a stage in stellar evolution where the core of a red giant star becomes hot enough to start fusing helium into carbon, which is achieved through the triple-alpha process.
Once the helium in the core is exhausted, the star can no longer maintain fusion reactions in the core. Fusion continues in shells around the core, making the star expand and cool into a red giant state once again.
The planetary nebulae are ejected outer layers of the star, illuminated by the ultraviolet radiation from the central star. Eventually, the core stabilizes as a white dwarf, which is a small, dense, and typically hot celestial body that represents the final evolutionary state of stars like the Sun.
Stars with core masses less than 1.4 solar masses will end up as white dwarfs after they exhaust their fuel, while those with larger core masses may become neutron stars or, if the core mass exceeds about 3 solar masses, black holes.