The Sharpless Catalog

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Sh 2-181

Coordinates: (122.7°, 2.33°)
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Radio observations and modelling suggest that Sh 2-181 is an HII region ionised by a B0 to B0.5 class star. A 1978 paper identifies the ionising star as the B1 V class LS I +64 47. The nebula is connected to the Cas OB7 association in the Perseus arm.

Sh 2-182

Coordinates: (122.81°, 1.87°)
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Avedisova suggests that Sh 2-182 is ionised by the B3 Ia supergiant HD 4694.

More recent studies, however, conclude that Sh 2-182 appears to be a reflection nebula (not an HII region) and may be associated with the infrared source and protoplanetary nebula IRAS 00470+6429.

Sh 2-183

Coordinates: (123.2°, 2.83°)
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This is an apparently large and distant HII region that is obscured by foreground dust. It consists of 44 thousand solar masses of ionised gas and is at least 3.9 million years old. The stars ionising the gas are unknown and are probably obscured by the foreground dust.

Avedisova locates Sh 2-183 in star formation region SFR 123.20+2.83, with 16 components, including a water maser and 8 infrared sources. One of these infrared sources is the young stellar object IRAS 00468+6527.

This object shows an extended irregular structure at radio frequencies as this 2.7 GHz image taken with the Effelsberg 100m radio telescope reveals.

I've used IPHAS hydrogen-alpha data to create a black and white image of this highly obscured nebula here.

Sh 2-183 is visible as a diffuse nebula bordered by more compact emission sources in this IRAS infrared image.

If this object is really located at 7000 parsecs, then the size in the radio image suggests that it may be one of the largest star formation regions in the outer galaxy. Note, however, that streaming motions in the Perseus arm can result in exaggerated distance estimates if velocity data is used alone to determine an object's distance (and the current distance estimate is, indeed, based on gas velocity).

Sh 2-184

Coordinates: (123.1°, -6.3°)
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Often called NGC 281, this bright nebula located far below the galactic plane is also nicknamed the Pac Man nebula by amateur astronomers after a 1980s-era video game character.

IC 1590, the star cluster at the heart of the nebula, is about 3.5 million years old. The core of the star cluster IC 1590 is the trapezium system HD 5005, which ionises NGC 281 and contains an O5.5 class star.

The distance to NGC 281 has been accurately measured via radio parallax as 2820 +/- 240 pc.

It is highly unusual to find such a prominent nebula so far below the galactic plane and there is some evidence that it is on the edge of a superbubble that has blown out of the galactic plane, perhaps because of multiple supernova explosions.

This nebula is often the subject of astrophotographers and there are many beautiful images of it on the Internet. One interesting false-colour version was Astronomy Picture of the Day.

You can see a view of this nebula in infrared taken by the WISE satellite here.

Sh 2-185

Coordinates: (123.97°, -1.87°)
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Sh 2-185 consists of a pair of nebulae, IC 59 and IC 63, that according to Sharpless and other authorities is ionised and illuminated by the B0 IVpe subgiant Gamma Cassiopeiae. It is a combination of a reflection nebula and HII region.

Sh 2-185 lies in front of the Perseus arm Cas OB1 association as can be seen in this image but is much closer.

A much better image of Sh 2-185 can be found here.

Sh 2-186

Coordinates: (124.89°, 0.33°)
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Avedisova says that Sh 2-186 is ionised by the B0 III giant Hiltner 102 and is part of the Cas OB7 association. It contains the infrared cluster [BDS2003] 51.

Sh 2-187

Coordinates: (126.66°, -0.8°)
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This young (100-200 thousand years) star formation region is most likely ionised by a B0 class star and is surrounded by a 4600 solar mass molecular cloud. It is partially obscured by the Lynds dark nebula LDN 1317 and contains the infrared star cluster [BDS2003] 52.

Russeil lists three potential ionising stars, one with a B2.5V class.

You can view a good visual image here of this rarely photographed object and a fuzzy hydrogen-alpha image created from IPHAS data here.

This nebula is prominent in infrared as can be seen in this MSX image.

Sh 2-188

Coordinates: (128.07°, -4.12°)
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This is a planetary nebula with an expansion age of 7500 years.

You can view a more detailed image of this nebula here.

Phil Plait calls this the "Firefox Nebula".

Sh 2-189

Coordinates: (131.58°, 2.66°)
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This faint and distant purple ball is a planetary nebula also called Abell 3.

Sh 2-190

Coordinates: (134.81°, 0.94°)
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The Heart nebula is ionised by the IC 1805 star cluster, which is part of the Cas OB6 association, and is the location of the W3 / W4 radio sources.

Avedisova places this nebula in star formation region SFR 133.69+0.99 with 86 components including 11 masers. IC 1805 contains at least 10 O-class stars including 3 extremely rare ultra-hot O4 and O5 class stars.

The correct distance to the W3 (OH) star formation region within Sh 2-190 has been measured with incredible accuracy using radio parallax as 2070 +10 / -20 pc.

For more information see the Heart and Soul (140° - 130°) sector description in the Commentary on the Galactic Plane.

You can view a stunning image of the larger Heart and Soul region here.

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.