220128 - IC2118 "Witch Head" nebula wRigel
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click image to enlarge
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ASTRO:
type=Supernova remnant const=Eridanus mag=13 dist=900 ly size= 50 ly other=bright star is "Rigel", blue supergiant 21 x solar masses dist=860 ly IMAGE: location=EB Driveway BrtlCls=4 moon=10% WnCr exposure=DSLR OSC: 70x120s (2.3h), ISO800, f/5.1 EQUIPMENT: camera=Nikon D90 (mod) optics=Nikkor70-300mm FX zoom @ 200mm filter=IRIX Edge LPS mount=Celestron AVX EQ guiding=Orion 60x240mm, ZWO ASi244MC SOFTWARE: acquisition=Stellarium, APT, PHD2, processing=PixInsight, RCAstro, PhotoshopCC, APF-R, LrC |
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Does this nebula look like the head of a witch? The nebula is known popularly as the "Witch Head" nebula (catalogued as IC 2118) because, it is said, the nebula's shape resembles a Halloween-style caricature of a witch's head. Exactly how, though, can be a topic of imaginative speculation. What is clear is that IC 2118 is about 50 light-years across and made of gas and dust that 'points' to -- because it has been partly eroded by -- the nearby star Rigel.
One of the brighter stars in the constellation Orion, Rigel is the bright star to the right of the featured image. The light color of the Witch Head Nebula is caused not only by Rigel's intense blue starlight but because the dust grains scatter light more efficiently than they emit red light. The same physical process causes Earth's daytime sky to appear light, although the scattering particles in planet Earth's atmosphere are molecules of nitrogen and oxygen which are the cause of our sky's blue color.
The Witch Head is an extremely faint reflection nebula believed to be an ancient supernova remnant. It lies about 900 light-years from Earth. Radio observations show a substantial presence of carbon monoxide throughout parts of IC 2118, an indicator of the presence of molecular clouds and star formation in the nebula. In fact, candidates for pre-main sequence stars and some classic T-Tauri stars have been found deep within the nebula.
The molecular clouds of IC 2118 are probably juxtaposed to the outer boundaries of the vast Orion-Eridanus bubble, a giant supershell of molecular hydrogen blown by the high mass stars of the Orion OB1 association. As the supershell expands into space, favorable circumstances for star formation occur. IC 2118 is located in one such area. The wind-blown appearance and cometary shape of the bright reflection nebula is highly suggestive of a strong association with the high mass luminous stars of Orion OB1. The fact that the heads of the cometary clouds of IC 2118 point northeast towards the association is strong support of that relationship.
One of the brighter stars in the constellation Orion, Rigel is the bright star to the right of the featured image. The light color of the Witch Head Nebula is caused not only by Rigel's intense blue starlight but because the dust grains scatter light more efficiently than they emit red light. The same physical process causes Earth's daytime sky to appear light, although the scattering particles in planet Earth's atmosphere are molecules of nitrogen and oxygen which are the cause of our sky's blue color.
The Witch Head is an extremely faint reflection nebula believed to be an ancient supernova remnant. It lies about 900 light-years from Earth. Radio observations show a substantial presence of carbon monoxide throughout parts of IC 2118, an indicator of the presence of molecular clouds and star formation in the nebula. In fact, candidates for pre-main sequence stars and some classic T-Tauri stars have been found deep within the nebula.
The molecular clouds of IC 2118 are probably juxtaposed to the outer boundaries of the vast Orion-Eridanus bubble, a giant supershell of molecular hydrogen blown by the high mass stars of the Orion OB1 association. As the supershell expands into space, favorable circumstances for star formation occur. IC 2118 is located in one such area. The wind-blown appearance and cometary shape of the bright reflection nebula is highly suggestive of a strong association with the high mass luminous stars of Orion OB1. The fact that the heads of the cometary clouds of IC 2118 point northeast towards the association is strong support of that relationship.