The Sharpless Catalog

Click on the small images to see larger ones.

Navigate to nebula [ Previous | Next ]

Sh 2-251

Coordinates: (189.86°, -27.18°)
[ See details ]

Sh 2-250 and Sh 2-251 appear to be areas of nebulosity within the Orion-Eridanus superbubble, like Sh 2-245. The superbubble is ionised by ultraviolet radiation from the hot stars of the Ori OB1 association.

Sh 2-252

Coordinates: (190.04°, 0.49°)
[ See details ]

The Monkey nebula (NGC 2174, also called the Monkey's Head nebula) contains five star clusters, including two which form the stellar group NGC 2175. It lies in the Perseus arm within the Gemini giant molecular clouds. By far the most important source of ionising radiation is the O6.5 V class star HD 42088.

Sh 2-252 may be connected to Sh 2-247 by CO clouds.

For more information on this complex region, see the Gem OB1 section of the description of the Jellyfish (190° - 180°) sector in the Commentary on the Galactic Plane.

Sh 2-253

Coordinates: (192.24°, 3.59°)
[ See details ]

Sh 2-253 is ionised by stars in the Bochum 1 star cluster, including the B 1.5 V class LS V +20 40.

For more information including detailed references, see the Orion (200° - 190°) sector description in the Commentary on the Galactic Plane.

Sh 2-254

Coordinates: (192.49°, -0.15°)
[ See details ]

The Sh 2-254 to Sh 2-258 HII regions are embedded in a molecular cloud with 27 thousand solar masses of gas and dust. The dense central core of the cloud, which includes the young massive cluster S255-2, is located between the two bright nebulae Sh 2-255 and Sh 2-257. This star formation complex, catalogued by Avedisova as 192.60-0.05, contains 6 ionising stars, a massive proto stellar cluster (Sh 2-255N), three infrared clusters and 11 masers.

Sh 2-254 is the large faint nebula at the right of this image.

This labelled image identifies the position of each nebula.

For more information on this star formation region and detailed references, see the Gem OB1 section of the description of the Orion (200° - 190°) sector of the Commentary on the Galactic Plane.

Sh 2-255

Coordinates: (192.64°, -0.01°)
[ See details ]

Also called IC 2162. Part of the Sh 2-254 to Sh 2-258 star formation region.

Sh 2-255 is the bright nebula at the left of this image.

Sh 2-256

Coordinates: (192.62°, -0.13°)
[ See details ]

Part of the Sh 2-254 to Sh 2-258 star formation region.

Sh 2-256 is the small dim nebula to the lower right of the two bright nebulae in this image.

Sh 2-257

Coordinates: (192.61°, -0.07°)
[ See details ]

Part of the Sh 2-254 to Sh 2-258 star formation region.

Sh 2-257 is the bright nebula at the middle of this image.

Sh 2-258

Coordinates: (192.73°, 0.05°)
[ See details ]

Part of the Sh 2-254 to Sh 2-258 star formation region.

Sh 2-258 is the dim nebula barely visible at the far left of this image. It can be seen more clearly in this labeled image.

Sh 2-259

Coordinates: (192.94°, -0.58°)
[ See details ]

This HII region lies in the direction of the Gem OB1 molecular clouds but its distance seems to make it a background object in the outer Cygnus arm. It is centred around the B1 V star ALS 18669.

Sh 2-260

Coordinates: (193.42°, -22.66°)
[ See details ]

This filamentary nebulosity is seen in the direction of the Orion-Eridanus superbubble. It is most likely associated with the Lambda Orionis ring (Sh 2-264) according to one source.

This Milky Way Explorer image shows that the nebula is in a similar direction as the B2 III giant HD 30836.

You can see a more detailed image of this little-studied nebula 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.