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Contains:  Witch Head nebula, IC 2118, The star λEri, The star ψEri
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Technical card

Resolution: 3035x2462

Frames: 15x900"

Integration: 3.8 hours job: 2517877

Locations: Gemini Observatory, LI JIANG, YUN NAN, China

Data source: Backyard


IC 2118 (also known as Witch Head Nebula due to its shape) is an extremely faint reflection nebula believed to be an ancient supernova remnant or gas cloud illuminated by nearby supergiant star Rigel in Orion. It lies in the Eridanus constellation, about 900 light-years from Earth. The nature of the dust particles, reflecting blue light better than red, is a factor in giving the Witch Head its blue color. Radio observations show substantial carbon monoxide emission 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.[1]

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 the interstellar medium, 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 IC2118 point northeast towards the association is strong support of that relationship.

The origin of IC 2118 is not precisely known, however it is believed to be an ancient supernova remnant; certainly most gases capable of ionization seem to have dissipated long ago - there is hardly any trace of Ha emission, though there may be residual OIII emission, suggested by some slightly greenish parts of the nebula.



Shenyan Zhang
License: None (All rights reserved)





15*3=45分钟的曝光。镜头光圈F2.8 没想到短时间内就能把周边暗云全部曝光出来。这个区域会进行2*2以上的马赛克。希望能够完成拍摄。




            Shenyan Zhang