The Sharpless Catalog

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Sh 2-161

Coordinates: (111.87°, 1.06°)
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Sh 2-161 is a large diffuse nebula surrounding the much smaller (and better studied) Sh 2-158, which is visible in the bottom right of this image.

The BFS catalog argues that Sh 2-161 is actually two distinct nebulae in the same line of sight, which they designate Sh 2-161a and Sh 2-161b. (Sharpless himself made no such distinction.)

Curiously, however, the distance estimates given in the scientific literature for the two nebulae are almost identical despite the quite different velocities quoted for the gas in this direction.

Sh 2-162

Coordinates: (112.2°, 0.2°)
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This is the Bubble nebula, NGC 7635, a circular shell around the O6.5 IIIf star BD +60°2522. The nebula also contains the infrared cluster [BDS2003] 44.

You can see the faint nebulosity around the Bubble in this Astronomy Picture of the Day.

The Bubble nebula is also bright at radio frequencies.

Sh 2-163

Coordinates: (113.6°, -0.7°)
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According to Avedisova, this nebula is ionised by the O 9.5 V class star LSI +60 8. It contains the infrared cluster [BDS2003] 45.

Russeil combines Sh 2-163, Sh-164 and Sh 2-166 into a single star formation region.

The nebula can be seen as a faint ring in this MSX infrared image.

Sh 2-164

Coordinates: (113.9°, -1.62°)
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According to Avedisova, this nebula is ionised by the B1 Ib supergiant LS I +59 10 which agrees with the class given by SIMBAD. Russeil also identifies it as the ionising star but gives a B0.2 II giant class.

Russeil combines Sh 2-163, Sh-164 and Sh 2-166 into a single star formation region.

Sh 2-165

Coordinates: (114.61°, 0.22°)
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Ionised by the B0 V star BD +61 +2494 and contains the infrared cluster [BDS2003] 46.

This nebula has a prominent ring structure in infrared as can be seen in this MSX image.

Sh 2-166

Coordinates: (114.63°, -0.79°)
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This faint nebula, ionised by the O9.5 V star BD +60 2607, forms part of the Cas OB5 supershell. Avedisova places it in the star formation region SFR 114.63-0.79 along with a water maser, the radio source KR 82 and the young stellar object Mol 160.

Russeil combines Sh 2-163, Sh-164 and Sh 2-166 into a single star formation region.

A recent Spitzer study concluded that Mol 160 is 3000 times more luminous than the sun, is accreting matter from a 220 solar mass dust cocoon and has not yet undergone hydrogen fusion.

Sh 2-167

Coordinates: (114.98°, 3.18°)
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There is very little information in the scientific literature on this faint nebula.

Sh 2-167 was previously listed as a planetary nebula but is now believed to be an HII region. It appears in the direction of a large expanding shell around Cas OB5, but the available distance estimates suggest that it may lie much further away in the Outer/Norma arm.

The nebula can be seen in infrared in this MSX image.

Sh 2-168

Coordinates: (115.8°, -1.6°)
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Avedisova concludes that the HII region Sh 2-168 is ionised by the O9 V star LS I +60 50. SIMBAD gives a slightly cooler B0 V spectral class. This is in the direction of an expanding shell surrounding Cas OB5.

Avedisova places Sh 2-168 in the star formation region SFR 115.80-1.60 along with the radio source KR 84. The nebula includes the loose infrared cluster [BDS2003] 47 and the Herbig-Haro object GM 2-44.

You can find a more detailed colour image here and a black and white hydrogen-alpha image created from IPHAS data using the process described here.

This nebula is quite bright in infrared as this MSX 8μm image reveals.

Sh 2-169

Coordinates: (115.88°, -1.72°)
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A faint nebulosity near the direction of the much brighter Sh 2-168. Avedisova finds that it is ionised by the B0 III giant BD +59 2786.

Sh 2-170

Coordinates: (117.63°, 2.25°)
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Sh 2-170 lies in the direction of the Cas OB5 supershell.

There is some confusion about the designation of the ionising star.

A 1995 paper concludes that the sole exciting star of Sh 2-170 is DM +63 2093, an O8 V star of 31 solar masses. Avedisova agrees on the star but gives a slightly cooler O9 V class. Curiously, SIMBAD gives a G5 spectral class for this star.

Reed gives the name for the star in this location as LS I +64 11, which SIMBAD lists as the O9.5 multiple star BD +63 2093p. A 2004 paper agrees on the BD +63 2093p designation and agrees with Avedisova on the O9 V class. This paper also says that BD +63 2093p is a member of the small open cluster Stock 18 and estimates 910 +/- 90 solar masses for the hydrogen gas in the nebula.

A wider view of this object can be found here.

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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.