During the mainstream phase of stellar evolution, the outer layers expand and the core shrinks as the stars become red giants. Externally expanding outer layers are separated from the star by various actions. This part of the planet is called the Planetary Nebula. Named the Planetary Nebula, it has nothing to do with the Planet. Some scientists argue that it should be called an ejection nebula. Scientists estimate that 95% of the stars will pass through such a phase. Scientists have discovered a number of planetary nebulae.
At the end of the life of a star with a mass of about 1-8 solar masses, all planetary nebulae form. At the end of the life cycle, the Sun is expected to form a planetary nebula. Compared to the long stages of stellar evolution, they are relatively short-lived phenomena, probably lasting tens of thousands of years. Once the red giant’s atmosphere is scattered, it emits intense ultraviolet radiation from an open hot core, called the planetary nebula nucleus (P.N.N.).
A typical planetary nebula is about one light-year long and contains very rare gases, usually 100 to 10,000 particles per cm3. (In the Earth’s atmosphere, comparisons contain 2.5 × 10 ^ 19 particles per cm3.) Young planetary nebulae have the highest density, sometimes up to 10 ^ 6 particles per cm3. As nebulae age, their expansion causes their density to decrease. The mass of planetary nebulae ranges from 0.1 to 1 solar mass.
Planetary nebulae play a crucial role in the chemical evolution of the Milky Way, which expels more massive elements from the created stars into the interstellar medium into the Milky Way.