The Sharpless Catalog

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Sh 2-1

Coordinates: (347.22°, 20.24°)
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This combination HII region and reflection nebula is ionised by the B1V class star Pi Scorpii, a member of the nearby Upper Scorpius subgroup of the Sco OB2 association, which forms part of the Gould belt and the inner edge of the Orion spur.

Sh 2-2

Coordinates: (347.7°, 1.9°)
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This HII region surrounds the O6.5 Ia supergiant and X-ray eclipsing binary HD 153919. It is seen behind the closer star cluster NGC 6281.

HD 153919 is a runaway star ejected from the Sco OB1 star association in a supernova explosion about 2 million years ago.

Sh 2-3

Coordinates: (348.25°, 0.49°)
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This bubble, most commonly called RCW 120, is ionised by the O8 V star CGO 439. Distance estimates consistently place it relatively close by (about 1340 pc) in the Sagittarius arm.

Sh 2-4

Coordinates: (348.2°, -1.0°)
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Infrared imagery reveals that RCW 121 (Sh 2-4) and RCW 122 lie at the edge of an enormous bubble ionised by the star cluster Havlen-Moffat 1. This cluster is 2-4 million years old and contains the Wolf-Rayet stars WR 87 and WR 89 as well as several O-stars.

Sh 2-5

Coordinates: (348.97°, -0.54°)
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This large diffuse nebula lies in the same direction as the Wolf-Rayet star WR 89.

Infrared imagery reveals that RCW 123 (Sh 2-5) lies within an enormous bubble ionised by the star cluster Havlen-Moffat 1. This cluster is 2-4 million years old and contains the Wolf-Rayet stars WR 87 and WR 89 as well as several O-stars. Distance estimates place it in the Centaurus arm.

Sh 2-6

Coordinates: (349.7°, 0.8°)
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This is NGC 6302, the Bug nebula, the remains of a dying G V class star. You can see an amazing Hubble image of this planetary nebula.

Sh 2-7

Coordinates: (349.86°, 22.26°)
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Sh 2-7 is the core of a huge diffuse nebula and is ionised by the B0.2IVe subgiant binary Delta Scorpii, a member of the nearby Sco OB2 association.

Sh 2-8

Coordinates: (351.23°, 0.77°)
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This is NGC 6334, the Cat's Paw nebula. This complex of HII regions contains one larger bubble (Gum 63) adjacent to three smaller bubbles (Gum 61, Gum 62 and Gum 64b) in addition to several other partially obscured nebulae and at least eleven major infrared sources that are probably mostly cooler B stars.

It lies at the same distance as NGC 6357, the War and Peace nebula, and is separated from it by a dark cloud. Both are near the Sco OB4 association in the Sagittarius arm.

Sh 2-9

Coordinates: (351.31°, 17.01°)
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This combination reflection nebula and HII region is ionised by the B1 III variable giant Sigma Scorpii in the nearby Upper Scorpius subgroup of the Sco OB2 association.

Sh 2-10

Coordinates: (352.44°, 2.26°)
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This mysterious nebula, catalogued as RCW 130 and Sh 2-10, lies in the direction of the Sco OB4 association. Two Wolf-Rayet stars, WR 86 and WR 88, are visible towards its edge.

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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.