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An OB association is a young stellar association containing 10 to 100 massive stars of spectral classes O and B, i.e., blue and very hot; they form together in giant molecular clouds, whose residual gas, once the stars are formed, is blown away by the strong stellar wind. [31]
Its form also resembles the wings of a butterfly. The nebula was imaged by the Hubble Space Telescope in the 1990s. The primary component of the central binary is the hot core of a star that reached the end of its main-sequence life cycle, ejected most of its outer layers and became a red giant, and is now contracting into a white dwarf. It is ...
Planetary nebulae are the remnants of the final stages of stellar evolution for mid-mass stars (varying in size between 0.5-~8 solar masses). Evolved asymptotic giant branch stars expel their outer layers outwards due to strong stellar winds, thus forming gaseous shells while leaving behind the star's core in the form of a white dwarf. [25]
There are other highly evolved hot stars not generally referred to as blue giants: Wolf–Rayet stars, highly luminous and distinguished by their extreme temperatures and prominent helium and nitrogen emission lines; post-AGB stars forming planetary nebulae, similar to Wolf–Rayet stars but smaller and less massive; blue stragglers, uncommon ...
Rigel and the IC 2118 nebula which it illuminates.. It was once believed that blue supergiants originated from a "feeding" with the interstellar medium when stars passed through interstellar dust clouds, [11] [8] although the current consensus is that blue supergiants are evolved high-mass stars, a natural consequence of stellar evolution, larger and more luminous than main-sequence stars.
Researchers have unveiled intricate details of the star-forming region known as the Tarantula Nebula which lies 170,000 light years from Earth. Scientists map violent nebula to discover how stars ...
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.
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]