Iris Nebula (LBN 487, VDB 139) with surrounding dust

Iris Nebula
All Images Copyright Steve Cannistra

Please click here for a larger version (50%)

RA: 21h 02m 12s (J2000)
Dec: +68 degrees 03' 58" (J2000)

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, upside down  "hat" just below 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 older image of this region 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:
Dates:  August 25, 26, 2017
Scope:  Takahashi FSQ106 at f5 on the Takahashi NJP Mount
Autoguider:  SBIG ST-402 with 60mm guidescope, focal length 227mm
Camera:  Starlight XPress SX814 CCD camera at -20C, resulting in an image scale of 1.44 arcsec/pixel with the FSQ106
Filters:  Baader LRGB
Exposures:  Total exposure 14 hours
Post-processing:  Calibrated, aligned and stacked in Maxim, followed by DDP in ImagesPlus (IP).  Further processing in Photoshop CS (16 bit format)

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