Sh 2-178
Coordinates: (121.4°, 25.35°)
[ Catalog | Explorer | SIMBAD ]
There is very little in the scientific literature about this huge faint nebula located in a direction that is well above the galactic plane.
Sh 2-178 is associated with the giant molecular cloud known as the Polaris Flare. The region's overall nebulosity does not derive from hydrogen-alpha emission in the region itself but instead from dusty cirrus clouds that reflect the light of the Milky Way.
The nebula is visible at both radio and infrared frequencies. It is perhaps best seen in context as the brightest portion of a huge atomic hydrogen (HI) loop (GIRL G134+34) seen in this image. The loop is also visible in infrared in this IRAS image. In both cases, Sh 2-178 is the large emission region at the right.
The star in the image is the K2 III giant HD 5848, which has a Hipparcos distance of only 96 parsecs, so presumably it is a foreground star unrelated to the nebula.
Sh 2-178 is associated with the giant molecular cloud known as the Polaris Flare. The region's overall nebulosity does not derive from hydrogen-alpha emission in the region itself but instead from dusty cirrus clouds that reflect the light of the Milky Way.
The nebula is visible at both radio and infrared frequencies. It is perhaps best seen in context as the brightest portion of a huge atomic hydrogen (HI) loop (GIRL G134+34) seen in this image. The loop is also visible in infrared in this IRAS image. In both cases, Sh 2-178 is the large emission region at the right.
The star in the image is the K2 III giant HD 5848, which has a Hipparcos distance of only 96 parsecs, so presumably it is a foreground star unrelated to the nebula.
The star in the image is the K2 IIII giant HD 5848, which has a Hipparcos parallax of 10.43 mas = 96 parsecs. [SIMBAD]
Catalogue of far-infrared loops in the Galaxy. [1]
The loop which Sh 2-178 is part of is also called the North Celestial Pole Loop. [2]
Sh 2-178 is associated with the Polaris Flare and the region's overall nebulosity does not derive from hydrogen-alpha emission but instead from the reflected light of the Milky Way. [3] Allan Sandage first pointed out this class of high latitude reflection nebulae in 1976 [4] and they are now sometimes called integrated flux nebulae.
These reflection nebulae were recently examined in a 2010 paper which concludes that "both a substantial fraction of the diffuse high-latitude Hα intensity in regions dominated by Galactic cirrus dust and much of the variance in the high-latitude Hα background are the result of scattering by interstellar dust of Hα photons originating elsewhere in the Galaxy". [5]
Catalogue of far-infrared loops in the Galaxy. [1]
The loop which Sh 2-178 is part of is also called the North Celestial Pole Loop. [2]
Sh 2-178 is associated with the Polaris Flare and the region's overall nebulosity does not derive from hydrogen-alpha emission but instead from the reflected light of the Milky Way. [3] Allan Sandage first pointed out this class of high latitude reflection nebulae in 1976 [4] and they are now sometimes called integrated flux nebulae.
These reflection nebulae were recently examined in a 2010 paper which concludes that "both a substantial fraction of the diffuse high-latitude Hα intensity in regions dominated by Galactic cirrus dust and much of the variance in the high-latitude Hα background are the result of scattering by interstellar dust of Hα photons originating elsewhere in the Galaxy". [5]
Notes
1. ^ Könyves, V., Kiss, Cs., Moór, A., et al. (2007). "Catalogue of far-infrared loops in the Galaxy", Astronomy and Astrophysics, Vol. 463, 1227-1234. [2007A&A...463.1227K]
2. ^ Meyerdierks, H., Heithausen, A., & Reif, K. (1991). "The North Celestial Pole Loop", Astronomy and Astrophysics, Vol. 245, 247-256. [1991A&A...245..247M]
3. ^ Heithausen, Andreas & Thaddeus, Patrick (1990). "The Polaris Flare - Extensive molecular gas near the north celestial pole", The Astrophysical Journal, Vol. 353, L49-L52. [1990ApJ...353L..49H]
4. ^ Sandage, Allen (1976). "High-latitude reflection nebulosities illuminated by the galactic plane", The Astronomical Journal, Vol. 81, 954. [1976AJ.....81..954S]
5. ^ Witt, Adolf N., Gold, Benjamin, Barnes, Frank S., III, et al. (2010). "On the Origins of the High-latitude Hα Background", The Astrophysical Journal, Vol. 724, 1551-1560. [2010ApJ...724.1551W]
Distance estimates
200 pc [1984ApJ...279..125F]Links
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Most of the sources used to create these nebula descriptions are listed in the
notes section for each description. In some cases,
for example the Avedisova, Humphreys and Reed catalogs, the source is used extensively and is not listed in the
individual nebula descriptions. See this catalog overview
for more information on the catalogs and the general sources used
to create these descriptions and this introduction to HII regions
on the general history of this area of astronomy.
This image was created using the POSS-II/UKSTU data of the Digitized Sky Survey and SuperCOSMOS using the process described here.
According to my correspondence with the Royal Observatory Edinburgh and the Space Telescope Science Institute, I am allowed to use the POSS-II/UKSTU data to create and display images for non-commercial purposes so long as I include this fine print for the SuperCOSMOS data:
Use of these images is courtesy of the UK Schmidt Telescope (copyright in which is owned by the Particle Physics and Astronomy Research Council of the UK and the Anglo-Australian Telescope Board) and the Southern Sky Survey as created by the SuperCOSMOS measuring machine and are reproduced here with permission from the Royal Observatory Edinburgh.
and this acknowledgement taken from the DSS site:
The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions.
The Second Palomar Observatory Sky Survey (POSS-II) was made by the California Institute of Technology with funds from the National Science Foundation, the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation, and the Eastman Kodak Corporation.
The UK Schmidt Telescope was operated by the Royal Observatory Edinburgh, with funding from the UK Science and Engineering Research Council (later the UK Particle Physics and Astronomy Research Council), until 1988 June, and thereafter by the Anglo-Australian Observatory. The blue plates of the southern Sky Atlas and its Equatorial Extension (together known as the SERC-J), as well as the Equatorial Red (ER), and the Second Epoch [red] Survey (SES) were all taken with the UK Schmidt.
The "Second Epoch Survey" of the southern sky was made by the Anglo-Australian Observatory (AAO) with the UK Schmidt Telescope. Plates from this survey have been digitized and compressed by the ST ScI. The digitized images are copyright ? 1993-5 by the Anglo-Australian Observatory Board, and are distributed herein by agreement.
The "Equatorial Red Atlas" of the southern sky was made with the UK Schmidt Telescope. Plates from this survey have been digitized and compressed by the ST ScI. The digitized images are copyright ? 1992-5, jointly by the UK SERC/PPARC (Particle Physics and Astronomy Research Council, formerly Science and Engineering Research Council) and the Anglo-Australian Telescope Board, and are distributed herein by agreement.
The compressed files of the "Palomar Observatory - Space Telescope Science Institute Digital Sky Survey" of the northern sky, based on scans of the Second Palomar Sky Survey are copyright ? 1993-1995 by the California Institute of Technology and are distributed herein by agreement. The compressed files of the "Palomar Observatory - Space Telescope Science Institute Digital Sky Survey" of the northern sky, based on scans of the Second Palomar Sky Survey are copyright ? 1993-1995 by the California Institute of Technology and are distributed herein by agreement.