The Sharpless Catalog

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Sh 2-171

Coordinates: (118.41°, 4.68°)
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This expanding shell of gas and dust was created by the original star cluster at the heart of the Cep OB4 association, which has now dispersed. It is now lit and ionized by the young star cluster Berkeley 59 (forming the bright nebula called Cederblad 214) and it is expanding into the fainter diffuse nebula NGC 7822. Berkeley 59 is surrounded by another dark region of disturbed gas and dust containing the radio source W1.

Avedisova lists 4 O-stars that ionise this nebula. The hottest of these is the O7 V BD +66 1675. She places Sh 2-171 in star formation region SFR 118.41+4.68 with 46 components, including 3 masers, 14 infrared sources and the dark nebula LDN 1271.

A 2008 study adds a fifth ionising O-star to Berkeley 59, hotter than than any of the ones Avedisova identified. Spectographic analysis reveals that BD +66 1673 has a class of O5 V((f))n. The same study concludes that Berkeley 59 is 2 million years old. A second 2008 study agrees on the age and comments that Berkeley 59 has nine ionising stars in total (classes O-B3).

There are more details on this nebula in the Cep OB4 section of the description of the Brain and Bubble (120° - 110°) sector of the Commentary on the Galactic Plane. You can also see the location of Cep OB4 and Sh 2-171 within the relatively nearby Cepheus molecular clouds on this face-on map.

You can see a spectacular image of this region here and view the large shell surrounding the nebula in visual light and in this IRAS infrared image.

Sh 2-172

Coordinates: (118.62°, -1.33°)
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Sh 2-172 contains the loose infrared cluster [BDS2003] 48.

Russeil combines Sh 2-172, Sh 2-173 and Sh 2-177 into one star formation region and comments that no stellar distance is known for Sh 2-172. All three nebulae lie in the direction of the expanding shell of gas and dust surrounding the Cas OB5 association.

Sh 2-173

Coordinates: (119.43°, -0.94°)
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Russeil combines Sh 2-172, Sh 2-173 and Sh 2-177 into one star formation region. All three nebulae lie in the direction of the expanding shell of gas and dust surrounding the Cas OB5 association.

Russeil identifies 7 possible ionising stars for Sh 2-173, the hottest of which is the O9 V star ALS 6151 (BD +60 39).

Avedisova associates Sh 2-173 with the star cluster NGC 103, the radio source KR 98, and the dark nebula LDN 1282.

Sh 2-173 appears to be on the edge of the HI shell GSH 117.8+1.5-35 associated with Cas OB5.

You can view detailed IPHAS hydrogen-alpha images of this nebula here.

Sh 2-174

Coordinates: (120.28°, 18.39°)
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The former central star of this old planetary nebula, the white dwarf GD 561, has drifted to the outside of the nebula.

A good image of this nebula can be found here.

Sh 2-175

Coordinates: (120.36°, 1.94°)
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Sh 2-175 appears in the direction of a supershell of molecular and atomic hydrogen clouds surrounding the Cas OB5 association, which is part of the Perseus arm. A widely varying range of distances to this nebula and its potential ionising star has been published in the scientific literature.

Avedisova gives the ionising star of Sh 2-175 as LS I +64 26 (O9.5 V), which Humphreys lists as a field star outside of any OB association.

Russeil concludes that LS I +64 26 is actually a B1.5 V star at 1090 +/- 210 parsecs and locates Sh 2-175 at this much closer distance.

You can read more about this region (with full references) in this galactic plane commentary.

Sh 2-176

Coordinates: (120.25°, -5.49°)
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This is a planetary nebula. The central star is a blue subdwarf.

You can find a good image of this nebula here.

Sh 2-177

Coordinates: (120.68°, -0.09°)
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Sharpless and Avedisova both conclude that Sh 2-177 is ionised by the O9 V star BD +61 105.

Russeil combines Sh 2-172, Sh 2-173 and Sh 2-177 into one star formation region. All three nebulae lie in the direction of the expanding shell of gas and dust surrounding the Cas OB5 association.

You can view a good image of this irregular diffuse nebula here.

Sh 2-178

Coordinates: (121.4°, 25.35°)
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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 2-179

Coordinates: (121.68°, 0.01°)
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This is the planetary nebula PN BV 5-2 (sometimes designated PN BV-2).

Sh 2-180

Coordinates: (122.63°, 0.05°)
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Sh 2-180 is visible in the direction of the Perseus arm Cas OB7 association, but a distance estimate based on CO velocity places it much further away in the Norma/Outer arm.

Avedisova also locates it at a large distance and concludes that it is ionised by the O7.5V star LS I +62 139.

The filaments visible in this image, more characteristic of a close supernova remnant than a distant HII region, suggests that this region may deserve deeper investigation.

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Stewart Sharpless published the second and final version of his famous nebula catalog in 1959. Although astronomers publish articles referring to the Sharpless nebulae almost every month, there seems to be few places on the Internet that bring together information on these nebulae as a whole - unlike, for example, the Messier catalog. This is most likely because the Messier objects are visible to anyone with a pair of binoculars or a small telescope. Most of the Sharpless objects are clearly visible only in CCD images or in photographic plates taken by large telescopes. Fortunately some of these plates have now been digitally scanned and made publicly available.

Many of the brightest and most beautiful Milky Way star formation regions visible from the northern hemisphere are in the Sharpless catalog so the 313 objects it contains are well worth examining carefully. (In fact there are more than 313 objects as subsequent research has shown that some of the Sharpless nebulae consist of more than one object.) Although the Sharpless catalog is only intended to be complete for objects visible north of declination -27 degrees, a similar catalog covering the southern hemisphere was published by Alex Rodgers, Colin Campbell, and John Whiteoak in 1960, which is largely an expansion of Colin Gum's earlier catalog. You can visit a gallery of these RCW nebulae here. At least 50 objects in the Sharpless catalog are also in the RCW catalog and I have noted this in the descriptions of these objects.

Most of the images used to illustrate the Sharpless catalog were created using the POSS-II/UKSTU data of the Digitized Sky Survey, or, where available, the more detailed SuperCOSMOS Sky Survey. In both cases, green = UKST Infrared. Because green represents infrared, the images are not quite the same as would be seen at purely visual frequencies. Green in these images usually reveals warm dust or red giant stars.

These images were 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.