The Sharpless Catalog

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Sh 2-241

Coordinates: (180.9°, 4.13°)
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This nebula is ionised by the O9V star LS V +30 31. The nebula is a blister on the side of a molecular cloud. This field also contains the reflection nebula vdB 65, which is a completely unrelated object at 1100 parsecs.

Avedisova places this nebula in star formation region 180.90+4.13 with two water masers and the emission star MWC 790.

You can view a more detailed image here.

Sh 2-242

Coordinates: (182.36°, 0.18°)
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According to Avedisova, this HII region is ionised by the B0 V class star BD +26 980. The distance estimates place it in the Perseus arm.

Sh 2-243

Coordinates: (184.08°, -4.17°)
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There is no visible nebulosity on this image, no known ionising stars in this direction, nor has anything been detected at radio frequencies. It is not clear whether this object actually exists.

Sh 2-244

Coordinates: (184.6°, -5.8°)
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This is the Crab nebula supernova remnant (M1), the remains of a star known to have exploded in the year 1054.

Sh 2-245

Coordinates: (186.35°, -34.32°)
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Sometimes called the Fishhook nebula, Sh 2-245 is one of the largest nebulae in apparent extent in the Sharpless catalog. It appears as a bright hydrogen-alpha ridge towards the southern end of the Orion-Eridanus superbubble. The Orion-Eridanus superbubble is ionised by the total ultraviolet radiation from the Ori OB1 association.

You can see a false colour image of the Fishhook nebula here.

Sh 2-246

Coordinates: (186.96°, -16.58°)
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Sh 2-246 is visible in the direction of Lynds dark cloud LDN 1562, which together with Lynds dark cloud LDN 1563 forms a local dust ridge located well below the galactic plane at a distance of 180 pc, and is part of the Taurus dark cloud complex, which is inside the Gould belt, our local galactic neighbourhood.

BFS provide no distance estimate for this nebula but note "Bright dark cloud".

Avedisova concludes that Sh 2-246 and LDN 1562 are part of the same star formation region, SFR 186.96-16.58. If Sh 2-246 is actually embedded in this dust ridge, it must be much closer than the distance estimate given here.

Sh 2-247

Coordinates: (188.93°, 0.79°)
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According to a 1989 study, Sh 2-247 is part of the Gem OB1 association, contains 37 thousand solar masses of gas and dust at a distance of 2200 pc, and appears to be physically connected through CO filaments with Sh 2-252. It is ionised by the B0 III giant LS V +21 27.

Avedisova places Sh 2-247 in the complex star formation region SFR 188.93+0.79 with 51 components, including 9 masers, several infrared star clusters, at least 4 molecular clouds, and the young stellar object IRAS 06058+2138. In 1984 she gave a 3500 pc distance estimate but corrected this to 2000 pc in 1989.

The available distance estimates suggests a location on the near side of the Perseus arm.

Sh 2-248

Coordinates: (189.1°, 2.9°)
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This is the Jellyfish nebula, a 3000-year-old supernova remnant (SNR 189.1+03.0, Gem A, IC 443).

You can see a beautiful image of IC 443 and the HII region Sh 2-249 here.

Sh 2-249

Coordinates: (189.01°, 4.02°)
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This HII region is ionised by members of the Gem OB1 association. Avedisova lists 3 B-class ionising stars (HD 43753, HD 43818 and HD 255091). Humphreys places all three of these stars in Gem OB1.

Avedisova places Sh 2-249 in star formation region SFR 189.01+4.02 along with the smaller HII region BFS 51, three reflection nebulae, and the dark nebulae LDN 1564, LDN 1567, and LDN 1568.

The relationship between Sh 2-249 and the adjacent supernova remnant Sh 2-248 (IC 443) is unclear. A 1984 paper concluded that Sh 2-249 is not a foreground source for IC 443 implying that it may be further away than the supernova remnant.

You can see a beautiful image of the supernova remnant Sh 2-248 (IC 443) and Sh 2-249 here.

Sh 2-250

Coordinates: (189.62°, -24.82°)
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Sh 2-250 is the brightest portion of an extremely faint ring surrounding the B2.5Vne class emission star HD 29441. It is located in the direction of the Orion-Eridanus superbubble surrounding the Ori OB1 association.

You can see the ring and the nebula position here and the star position here.

You can see an interesting image of the faint nebulosity in this direction 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.