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Still other nebulae form as planetary nebulae. This is the final stage of a low-mass star's life, like Earth's Sun. Stars with a mass up to 8–10 solar masses evolve into red giants and slowly lose their outer layers during pulsations in their atmospheres.
All planetary nebulae form at the end of the life of a star of intermediate mass, about 1-8 solar masses. It is expected that the Sun will form a planetary nebula at the end of its life cycle. [8] They are relatively short-lived phenomena, lasting perhaps a few tens of millennia, compared to considerably longer phases of stellar evolution. [9]
The table shows the lifetimes of stars as a function of their masses. [1] All stars are formed from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.
Planetary nebulae, represented here by the Ring Nebula, are examples of emission nebulae. An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star .
A planetary nebula is formed in the late stage of the evolution of a sun-like star. After having steadily produced energy for several billion years through the nuclear fusion of hydrogen into helium in its central region, or core, the star undergoes a series of energy crises related to the depletion of hydrogen and subsequent contraction of the core.
The W51 nebula in Aquila - one of the largest star factories in the Milky Way (August 25, 2020). Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars. [1]
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Nebulae become visible if the gas glows, or if the cloud reflects starlight or obscures light from more distant objects. The catalogues that it may refer to: Catalogue des nébuleuses et des amas d'étoiles (Messier "M" catalogue) first published 1771; Catalogue of Nebulae and Clusters of Stars (William Herschel 'CN'/"H" catalogue) first ...