The Sharpless Catalog

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Sh 2-11

Coordinates: (353.19°, 0.84°)
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The HII region NGC 6357, also called W 22 or the War and Peace Nebula, is ionised by the Pismis 24 and AH03 J1725−34.4 star clusters. Pismis 24 includes the multiple O4 and O4-5 star system [N78] 35 according to a 1984 paper. (SIMBAD gives a cooler O7 III class for this star.)

Near by is the Wolf-Rayet star WR 93, which is also a multiple star system with a class O7-9 companion.

The Cat's Paw nebula NGC 6334 lies at approximately the same distance and is separated from it by a dark cloud. You can see both nebulae together in this image.

An amazing closeup of part of this nebula can be seen in this Hubble image.

Sh 2-12

Coordinates: (355.4°, 0.2°)
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This diffuse nebula is ionised by the binary O-star (O7V + O7V) HD 159176 in the star cluster NGC 6383.

Sh 2-13

Coordinates: (355.9°, 1.5°)
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This nebula surrounds the O9.5V binary HD 158186, which lies in the direction of the small cluster Antalova 1.

Sh 2-14

Coordinates: (357.1°, 2.1°)
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This nebula appears as a faint blue haze in the direction of the constellation Scorpius.

There are no significant references in the scientific literature for this object and indeed the BFS catalog removes Sh 2-14 from its revised Sharpless catalog because Blitz, Fich and Stark could not detect it.

Sh 2-15

Coordinates: (358.34°, -1.85°)
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This HII region is ionised by the O8 V star HD 161853 and is part of the Sh 2-15 to Sh 2-20 complex of HII regions located in the Sgr OB5 association in the Sagittarius arm. It is the location of the radio source W25.

Sh 2-16

Coordinates: (0.0°, -0.6°)
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Sh 2-16 is part of the Sh 2-15 to Sh 2-20 complex of HII regions located in the Sgr OB5 association in the Sagittarius arm. It appears to be ionised by the O9.5 V star LSS 4381.

Sh 2-17

Coordinates: (0.02°, 0.13°)
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Sh 2-17 is part of the Sh 2-15 to Sh 2-20 complex of HII regions located in the Sgr OB5 association in the Sagittarius arm.

There are no papers suggesting ionising stars for Sh 2-17 and there are no OB stars in this direction in the Reed OB star catalog either. However, the infrared cluster [DB2000] 58 appears to be embedded in the nebula and may contain the ionising stars.

Sh 2-18

Coordinates: (0.1°, -0.8°)
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This small nebula is part of the Sh 2-15 to Sh 2-20 complex of HII regions located in the Sgr OB5 association in the Sagittarius arm. It lies next to RCW 140 (Sh 2-19).

No ionising stars are cited in the scientific literature but the nebula is believed to contain the infrared cluster [DB2000] 1 which may perhaps contain ionising stars.

Sh 2-19

Coordinates: (0.11°, -0.56°)
[ See details ]

This nebula is part of the Sh 2-15 to Sh 2-20 complex of HII regions located in the Sgr OB5 association in the Sagittarius arm.

Sh 2-20

Coordinates: (0.33°, -0.19°)
[ See details ]

This nebula is part of the Sh 2-15 to Sh 2-20 complex of HII regions located in the Sgr OB5 association in the Sagittarius arm. It contains the infrared star clusters [DB2000] 5 and [DB2000] 6.

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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.