APOD: The Ghoul of IC 2118 (2020 Oct 29)

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APOD Robot
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APOD: The Ghoul of IC 2118 (2020 Oct 29)

Post by APOD Robot » Thu Oct 29, 2020 4:05 am

Image The Ghoul of IC 2118

Explanation: Inspired by the halloween season, this telescopic portrait captures a cosmic cloud with a scary visage. The interstellar scene lies within the dusty expanse of reflection nebula IC 2118 in the constellation Orion. IC 2118 is about 800 light-years from your neighborhood, close to bright bluish star Rigel at the foot of Orion. Often identified as the Witch Head nebula for its appearance in a wider field of view it now rises before the witching hour though. With spiky stars for eyes, the ghoulish apparition identified here seems to extend an arm toward Orion's hot supergiant star. The source of illumination for IC 2118, Rigel is just beyond this frame at the upper left.

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neufer
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Al Ghoul

Post by neufer » Thu Oct 29, 2020 1:41 pm

Click to play embedded YouTube video.
https://en.wikipedia.org/wiki/Algol wrote:
<<Beta Persei is the star's Bayer designation. The name Algol derives from Arabic رأس الغول raʾs al-ghūl : head (raʾs) of the ogre (al-ghūl) (see "ghoul"). The English name Demon Star was taken from the Arabic name. In Hebrew folklore, Algol was called Rōsh ha Sāṭān or "Satan's Head", as stated by Edmund Chilmead, who called it "Divels head" or Rosch hassatan. A Latin name for Algol from the 16th century was Caput Larvae or "the Spectre's Head". Hipparchus and Pliny made this a separate, though connected, constellation.>>
Art Neuendorffer

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Re: APOD: The Ghoul of IC 2118 (2020 Oct 29)

Post by johnnydeep » Thu Oct 29, 2020 4:23 pm

APOD Robot wrote:
Thu Oct 29, 2020 4:05 am
Image The Ghoul of IC 2118

Explanation: Inspired by the halloween season, this telescopic portrait captures a cosmic cloud with a scary visage. The interstellar scene lies within the dusty expanse of reflection nebula IC 2118 in the constellation Orion. IC 2118 is about 800 light-years from your neighborhood, close to bright bluish star Rigel at the foot of Orion. Often identified as the Witch Head nebula for its appearance in a wider field of view it now rises before the witching hour though. With spiky stars for eyes, the ghoulish apparition identified here seems to extend an arm toward Orion's hot supergiant star. The source of illumination for IC 2118, Rigel is just beyond this frame at the upper left.
I couldn't figure out how this smaller field "Ghoul" pic fit into the larger Witch Head nebula pic from 2018, and neufer helped me figure it out (see end of discussion at http://asterisk.apod.com/viewtopic.php?t=37945).

So, for anyone else who was wondering, here's the result (with the super bright star Rigel on the lower left, toward which the "Ghoul's" hand is gesturing):
Where 'The Ghoul of IC 2118' fits in 'The Witch Head Nebula'.JPG
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Ann
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Re: APOD: The Ghoul of IC 2118 (2020 Oct 29)

Post by Ann » Fri Oct 30, 2020 5:54 am

To really see the Witch Head Nebula, we need this orientation:

































Can you see the Witch's protruding chin, her gaping mouth and her knobbly nose? And even perhaps her empty eye socket?

Wikipedia wrote:

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 the constellation of Orion.
...
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.

What I would like to know is how nearby Rigel really is to the Witch Head Nebula. Clearly we are talking about a distance of many light years. Rigel is a bright star.

Note that while the Witch Head Nebula is a blue reflection nebula, it is not strongly blue. The bluest part of it appears to be around the nose and forehead of the witch, the central or middle part of the nebula. Perhaps the light from Rigel is not illuminating the other parts as strongly, or perhaps there is dust between us and the nebula in front of parts of the Witch Head, diluting the nebula's blue color.

Take a look at Bob Franke's picture of the Witch Head. There are clearly patches of brown dust in the nebula's "chin".

Ann
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