Iris Nebula (LBN 487 / VDB 139) with associated open cluster NGC 7023

Iris Nebula
All Images Copyright Steve Cannistra

Please click here for a medium sized view (40%)
Please click here for a larger sized view (50%)
Please click here for rollover showing an area imaged by Hubble in December 2009

Distance: 1,300 light years
RA: 21h 01m 31s
Dec: +68 degrees 10' 37"
PA: plus 237 degrees

The Iris Nebula is an interesting and beautiful reflection nebula in the constellation Cepheus.  Discovered by Herschel in 1794, this object is often mistakenly labeled for its associated open star cluster NGC 7023, which is present in the triangular "top hat" just above center in the image.  The Iris Nebula (LBN 487 / VDB 139) is illuminated by a central hot star named SAO 19158 (aka HD 200775), which is 10 times the mass of our sun.  Although not officially designated as an emission nebula, closer examination of the above image will reveal a linear ridge on either side of SAO 19158 that represents HII emission.  In addition to this small emission region, there is a much more extensive reflection component comprised of microscopic dust particles that preferentially scatter blue light from the central star.  The peripheral regions are comprised of reddish dust that obscures light from background stars.

In the center of the nebula, there are several ruddy-colored wisps and filaments of dust that emit broad band red light, instead of reflecting the more typical blue light of a reflection nebula.  These red regions represent extended red emission (ERE), which is a type of phospholuminescence associated with dust particles that are bombared by high energy UV radiation from SAO 19158.  Recent investigation of this region has revealed radiation in the near infrared range of the spectrum, thought to be related to the presence of polycyclic aromatic hydrocarbons in this region of space.  The Hubble Space Telescope imaged the central portion of the Iris Nebula in December of 2009, which I superimposed upon my image in this rollover, along with a link to the original Hubble report.

More information regarding the Iris Nebula may be found on Rob Gendler's website.

Photographic Details:
Date:  July 2 and 3, 2010 (Luminance); August 6 and 7 (RGB)
Scope:  Vixen VC200L at f6.4 on the Takahashi NJP Mount
Autoguider:  SBIG ST-402
Camera:  ST8300 -15C

Baader L, R, G, B filters
Exposures:  Lum- 70 x 5' = 350'; R- 15 x 8' = 120'; G- 10 x 10' = 100'; B- 12 x 15' = 180'. Total exposure 12.5 hours
Post-processing:  Calibrated in Maxim, aligned and stacked using DeepSkyStacker, followed by DDP in ImagesPlus (IP).  Further processing in Photoshop CS5. 

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