Clear night and Caldwell 4, the Iris Nebula (Chris Hunt)

Celestial hemisphere: Northern · Constellation: Cepheus (Cep) · Contains: Iris Nebula · NGC 7023 · VdB139

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Clear night and Caldwell 4, the Iris Nebula

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Clear night and Caldwell 4, the Iris Nebula

Some good luck and a clear and cool night in Minnesota brought these photons to my camera from the Iris Nebula. This nebula is a reflection nebula that lies 1300 light years away and about six light years across. Reflection nebulas are a little different than their big bright red emission nebulas that ionize gas and send out light that way. A reflection nebula has a bright nearby star that doesn't heat the gas enough to ionize it but instead reflects its light off the gas and dust (the Witch Head nebula is another reflection nebula I have shared before). They require reasonably dark skies to image and for the moon to stay away.....

The dense interstellar dust that can be seen in this image is so dense it blocks out light from many stars deep to it. Significant evidence exist that much of this dust is actually made up of dense PAHs (polycyclic aromatic hydrocarbons). PAHs are complex rings of carbon and hydrogen and one of the fundamental building blocks to abiotically generate the starting materials for some of the earliest forms of life. While this is a distant source, PAHs have been found closer to planet in the upper atmosphere of one of Saturn's moon (Titan). They can also be easily found on our own planet due to combustion of organic materials (forest fires for example) but also in coal and other fossil fuels.

For those of you bored by talk of aromatic hydrocarbon rings, the nebula is named for its relatively close resemblance to the common garden flower. If botany is not your thing and hydrocarbons leave you feeling empty, the Iris nebula is also featured in the game Halo 3....enjoy!

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Status	Advanced success
Started	...
Astrometry.net job	4481229
PixInsight job	OJ4WI7FTYRVXV9QFBNNAOOFVH6X4LKZ3
PixInsight queue size	n/a
PixInsight stage	n/a

RA (center)	21h01m25s.390
RA (top/left)	21h00m44s.651
RA (top/right)	21h08m40s.941
RA (bottom/right)	21h02m08s.630
RA (bottom/left)	20h54m13s.783

Dec (center)	+68°08′54″.10
Dec (top/left)	+67°28′06″.53
Dec (top/right)	+68°15′24″.72
Dec (bottom/right)	+68°49′41″.39
Dec (bottom/left)	+68°01′12″.74

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Clear night and Caldwell 4, the Iris Nebula

Clear night and Caldwell 4, the Iris Nebula

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Clear night and Caldwell 4, the Iris Nebula

Clear night and Caldwell 4, the Iris Nebula

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