The Sharpless Catalog

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Sh 2-121

Coordinates: (90.23°, 1.72°)
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The HII region Sh 2-121 is surrounded by an expanding shell containing about 39 solar masses of gas. The shell is at least 650 thousand year old and is likely driven by stellar winds from an O8.5 class star.

According to a 1978 study, Sh 2-120, Sh 2-121, Sh 2-127 and Sh 2-128 are all at about the same distance of 7500 parsecs and are "probably distant HII regions associated with a spiral feature more distant than the Perseus arm".

A 2003 paper reduces the distance to Sh 2-121 to 4500 ± 1000 parsecs, which could make it part of the Perseus arm.

Sh 2-122

Coordinates: (89.19°, -41.13°)
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Sh 2-122 is likely a reflection nebula illuminated by an embedded but unseen star and associated with the molecular cloud MBM 55, at a distance of 150 pc.

A good image of this nearby object can be found here.

Sh 2-123

Coordinates: (91.13°, -6.36°)
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Examining this region in hydrogen-alpha suggests that Sh 2-123 is joined to the equally mysterious Sh 2-113, Sh 2-114 and Sh 2-118 in a long ridge of nebulosity south and south-east of Sh 2-117, the North American nebula. Sh 2-114, Sh 2-118 and Sh 2-123 have distance estimates of about 4000 parsecs. If this ridge is also at 4000 parsecs, it must be enormous.

Sh 2-124

Coordinates: (94.48°, -1.55°)
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Although very little appears in the scientific literature on the mysterious HII region Sh 2-124, located some distance to the west of the Cep OB1 association, recent detailed hydrogen-alpha imaging done for the IPHAS project reveals the structure of this violin-shaped nebula in spectacular detail.

Infrared imaging from MSX reveals a bubble in this direction.

Felli and Harten give a list of 5 ionising stars, including the O7.5 class LS III +50 28, and support the BFS distance estimate of 2600 parsecs. However, other sources argue that this star may be too cool to be the ionising star.

Chini and Wink identify two uncatalogued ionising stars, with classes O7V and B2V, and give a distance estimate of 3600 parsecs.

Crampton, Georgelin and Georgelin give a kinematic distance (based on gas velocity) of 4400 parsecs.

Sh 2-125

Coordinates: (94.4°, -5.51°)
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The Cocoon nebula is associated with the star cluster IC 5146 and is ionised by the B0 V class star BD +46 3474 according to Avedisova.

This Astronomy Picture of the Day page contains a good large image and links for more information.

Sh 2-126

Coordinates: (95.38°, -16.8°)
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This relatively close HII region is also called the 10 Lacertae complex after its ionising star, the O9 V multiple star 10 Lacertae, which forms the core of the Lac OB1 association. The nebula also contains the young Orion type variable emission star LkHA 233.

Sh 2-127

Coordinates: (96.29°, 2.6°)
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Radio analysis reveals that Sh 2-127 consists of two distinct components - a larger weaker and more diffuse source (WB89 85A) to the northeast, consistent with ionisation by an O7 class star, and a stronger but smaller source to the southwest (WB89 85B), consistent with ionisation by an O8.5 class star. (However, it is also possible that both components are ionised by a single star.) Both components are located near the northwestern edge of a molecular cloud and are embedded in the molecular gas.

According to a 1978 study, Sh 2-120, Sh 2-121, Sh 2-127 and Sh 2-128 are all at about the same distance of 7500 parsecs and are "probably distant HII regions associated with a spiral feature more distant than the Perseus arm".

Sh 2-128

Coordinates: (97.5°, 3.16°)
[ See details ]

This one million year old HII region is ionised by an O7 star.

According to a 1978 study, Sh 2-120, Sh 2-121, Sh 2-127 and Sh 2-128 are all at about the same distance of 7500 parsecs and are "probably distant HII regions associated with a spiral feature more distant than the Perseus arm".

Sh 2-129

Coordinates: (98.5°, 7.97°)
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Sharpless notes that this large faint nebula is part of the Cep OB2 association and the Cepheus bubble.

Avedisova lists 5 B-class ionising stars.

Sometimes called the Flying Bat nebula. This image only shows part of this nebula.

Sh 2-130

Coordinates: (98.86°, 12.64°)
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This appears to be a reflection nebula.

Faint nebulosity surrounds the B5 star HD 197911, the A0 star HD 197809 and the G5 star SAO 18999. HD 197911 is a runaway star blasted from the heart of the Cep OB2 association by a supernova explosion 2-3 million years ago.

Navigate to nebula [ Previous | Next ]

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.