Hourglass Nebula Comparison Table

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physical object > natural object > celestial body > nebula > H II region > compact H II region > Hourglass Nebula

Up: compact H II region, planetary nebula

Hourglass Nebula comparison table

Subject has expansion velocity is a kind of has catalog is an instance of has synonym has image has definition has distance has composition

compact H II region H II region nebula catalog A dense (n_e ≥ 10³ cm^-3) H II region of small linear dimensions (≤ 1 pc). ionized hydrogen

planetary nebula typically 10 km/s expanding emission nebula planetary nebula catalog emission nebula An expanding envelope of rarefied ionized gas surrounding a hot white dwarf. The envelope receives ultraviolet radiation from the central star and reemits it as visible light by the process of fluorescence. The planetary nebula stage lasts for less than 50,000 years. During the core contraction that terminates the red-giant stage, the helium-burning shell is ejected at a velocity so high that it becomes separated from the core. Under current theories, a star with a carbon core and a mass greater than 0.6 M_sun (but less than 4 M_sun) will become a planetary nebula and leave behind a white dwarf. Planetary nebulae are now known to occur in stars less than 4 M_sun whose envelope becomes unstable during the hydrogen shell burning stage. enhanced with heavy elements relative to the interstellar medium

Hourglass Nebula typically 10 km/s planetary nebula catalog planetary nebula MyCn18 A compact H II region in the center of Lagoon Nebula. 8000 light-years away ionized hydrogen

Subject	has expansion velocity	is a kind of	has catalog	is an instance of	has synonym	has image	has definition	has distance	has composition
compact H II region		H II region	nebula catalog				A dense (n_e ≥ 10³ cm^-3) H II region of small linear dimensions (≤ 1 pc).		ionized hydrogen
planetary nebula	typically 10 km/s	expanding emission nebula	planetary nebula catalog		emission nebula		An expanding envelope of rarefied ionized gas surrounding a hot white dwarf. The envelope receives ultraviolet radiation from the central star and reemits it as visible light by the process of fluorescence. The planetary nebula stage lasts for less than 50,000 years. During the core contraction that terminates the red-giant stage, the helium-burning shell is ejected at a velocity so high that it becomes separated from the core. Under current theories, a star with a carbon core and a mass greater than 0.6 M_sun (but less than 4 M_sun) will become a planetary nebula and leave behind a white dwarf. Planetary nebulae are now known to occur in stars less than 4 M_sun whose envelope becomes unstable during the hydrogen shell burning stage.		enhanced with heavy elements relative to the interstellar medium
Hourglass Nebula	typically 10 km/s		planetary nebula catalog	planetary nebula	MyCn18		A compact H II region in the center of Lagoon Nebula.	8000 light-years away	ionized hydrogen

Up: compact H II region, planetary nebula