The Sharpless Catalog

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Sh 2-231

Coordinates: (173.37°, 2.55°)
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According to Avedisova, this visually faint nebula is ionised by the O9.5V class star LS V +35 24. Avedisova combines Sh 2-231 and Sh 2-233 into a single star formation region, 173.37+2.55, that contains 7 masers and numerous young stellar objects.

Sh 2-231 to Sh 2-235 form a complex of HII regions located together in the Perseus arm in the outer galaxy. This complex may be associated with an old (330 thousand years) supernova remnant, FVW 172.8+1.5.

There is a giant molecular cloud, G174+2.5, containing Sh 2-231, Sh 2-232, Sh 2-233, and Sh 2-235 that is at a distance of about 1800 pc.

Sh 2-232

Coordinates: (173.47°, 3.23°)
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This peculiar belted nebula is ionised by two giant stars: the O9.5 III HD 37737 and an anonymous B0 II class star according to Avedisova.

HD 37737 may be a runaway star and is a close binary with a period of 7.84 days.

Sh 2-231 to Sh 2-235 form a complex of HII regions located together in the Perseus arm in the outer galaxy. This complex may be associated with an old (330 thousand years) supernova remnant, FVW 172.8+1.5.

There is a giant molecular cloud, G174+2.5, containing Sh 2-231, Sh 2-232, Sh 2-233, and Sh 2-235 that is at a distance of about 1800 pc.

Sh 2-233

Coordinates: (173.36°, 2.44°)
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The visually obscured Sh 2-233 contains the high-mass proto star cluster IRAS 05358+3543 (Sh 2-233 IR).

Avedisova combines Sh 2-231 and Sh 2-233 into a single star formation region, 173.37+2.55, that contains 7 masers and numerous young stellar objects.

Sh 2-231 to Sh 2-235 form a complex of HII regions located together in the Perseus arm in the outer galaxy. This complex may be associated with an old (330 thousand years) supernova remnant, FVW 172.8+1.5.

(Sh 2-235 is the bright nebula dominating the left side of this image.)

There is a giant molecular cloud, G174+2.5, containing Sh 2-231, Sh 2-232, Sh 2-233, and Sh 2-235 that is at a distance of about 1800 pc.

Sh 2-234

Coordinates: (173.37°, -0.19°)
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This is IC 417, sometimes called the Spider nebula. Sharpless 2-234 and 2-237 are together sometimes called the Spider and the Fly.

IC 417 surrounds the star cluster Stock 8. Avedisova gives two ionising stars: HD 35619 (O7V) and BD +34 1054 (B0 IV). SIMBAD gives O9.5V for this second star.

Sh 2-231 to Sh 2-235 form a complex of HII regions located together in the Perseus arm in the outer galaxy. This complex may be associated with an old (330 thousand years) supernova remnant, FVW 172.8+1.5.

Sh 2-235

Coordinates: (173.61°, 2.8°)
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This kidney-shaped HII region is the intersection point of two massive giant molecular clouds (100 thousand and 300 thousand solar masses respectively) with intense star formation. Infrared analysis using the Spitzer space telescope has found 86 young stellar objects within Sh 2-235.

One of these molecular clouds, G174+2.5, contains Sh 2-231, Sh 2-232, Sh 2-233, and Sh 2-235 and lies at a distance of about 1800 pc.

Sh 2-235 is ionised by the O9.5 V star BD +35 1201. Avedisova places this nebula in star formation region SFR 173.61+2.80 with 54 components, including 7 masers, the smaller HI region BFS 46 and several Herbig-Haro objects.

Sh 2-231 to Sh 2-235 form a complex of HII regions located together in the Perseus arm in the outer galaxy. This complex may be associated with an old (330 thousand years) supernova remnant, FVW 172.8+1.5.

You can view a larger visual frequency image of Sh 2-235 here and an infrared image here.

Sh 2-236

Coordinates: (173.61°, -1.73°)
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Lying at the core of the Aur OB2 association, the great HII region IC 410 (associated with the radio source W8) surrounds the star cluster NGC 1893 and is sometimes called the Tadpole nebula because of tadpole like structures (the nebulae Sim 129 and Sim 130) visible in detailed images.

Avedisova lists 5 ionising stars (including 4 O-class stars). The hottest of these is the O5 V star HD 242908. She places Sh 2-136 in the star formation region SFR 173.63-1.70 along with the young stellar object IRAS 05198+3325.

A 2002 study states that NGC 1893 contains "at least five O-type stars".

There is an enormous range of distance estimates for NGC 1893. The most recent estimates appear to be converging around 3500 pc, consistent with a location in the Perseus arm.

Sh 2-237

Coordinates: (173.92°, 0.32°)
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Sometimes called the Fly nebula, this nebula surrounds the open cluster NGC 1931. Sharpless 2-234 and 2-237 are together sometimes called the Spider and the Fly.

Avedisova lists two B0 V class ionising stars: LS V +34 46 and LS V +34 47.

A more detailed image of Sh 2-237 is here.

Sh 2-238

Coordinates: (176.24°, -20.88°)
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Hind's nebula (NGC 1555, HH 155) is a Herbig-Haro nebula surrounding the young G5V class T Tauri triple variable star system within the Taurus dark cloud complex, which is inside the Gould belt, our local galactic neighbourhood.

Sh 2-239

Coordinates: (178.91°, -20.12°)
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Sh 2-239 is not a HII region but a reflection nebula and a collection of Herbig-Haro objects embedded in the dark cloud LDN 1551. The brightest part of Sh 2-239 is catalogued as the Herbig-Haro object HH 102. It is located near the star T Tauri within the Taurus dark cloud complex, which is inside the Gould belt, our local galactic neighbourhood.

Sh 2-240

Coordinates: (180.2°, -1.3°)
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This is the supernova remnant Sim 147 (SNR 180.0-01.7). Visit this site or this site for better and more comprehensive images of Sim 147.

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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.