The Sharpless Catalog

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Sh 2-301

Coordinates: (231.44°, -4.41°)
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According to Avedisova, Sh 2-301 is ionised by the O6 V star LSS 207 and the B1 V star LSS 212 and places it in star formation region SFR 231.44-4.41 along with several reflection nebulae including Bran 6 and Bran 7 A-D.

This HII region may be associated with the GS234-02 supershell.

You can see another image of this region here.

Sh 2-302

Coordinates: (232.56°, 0.89°)
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This HII region lies within the molecular cloud [JKK96] A and is located well in front of the GS234-02 supershell. It contains the infrared star cluster [DBS2003] 4. Avedisova concludes that it is ionised by stars associated with the Bochum 5 cluster, including the O9.5 V star HD 59986, and places it in star formation region SFR 232.56+0.89, along with several other HII regions and reflection nebulae including VDB 97.

The class for HD 59986 is supported by a 1995 paper by Russeil, the Georgelins and colleagues. SIMBAD, however, gives the class for HD 59986 as B5, which would make it too cool to be an ionising star.

Here's another image of this object from an astrophotographer who imaginatively calls it the Snowman nebula.

Sh 2-303

Coordinates: (233.35°, -9.47°)
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According to a 1982 study, this nebula is ionised by the Wolf-Rayet star WR 6 (EZ CMa) along with Sh 2-304 and Sh 2-308. However, a look at this region in hydrogen-alpha suggests that Sh 2-303 is the brightest part of a ring that appears to surround several B class giants, including LS 92 (B2/3 III) and HD 51200 (B2 III/IV). So it seems as though WR 6 may not be the only ionising star for this nebula.

Avedisova includes Sh 2-303 = Bran 3 in the star formation region SFR 233.40-9.42 along with the smaller nebula Bran 1.

Sh 2-304

Coordinates: (233.88°, -12.39°)
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According to a 1982 study, this nebula is ionised by the Wolf-Rayet star WR 6 (EZ CMa) along with Sh 2-304 and Sh 2-308. However, a look at this region in hydrogen-alpha suggests that Sh 2-304 lies at some distance from WR 6 and forms the brightest portion of a long ridge that lies below the large Gum 8 / Sh 2-310 HII region. The ridge may be ionised by the combined radiation from the many hot stars in this region.

Sh 2-305

Coordinates: (233.8°, -0.2°)
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Sh 2-305 is ionised by at least two O-class stars ([VM75] Sh 2-305 4 (O8.5 V) and [VM75] Sh 2-305 2 (O9.5 V)), and possibly two B0 class stars as well. It contains the loose infrared cluster [DBS2003] 5.

Avedisova places this nebula in star formation region SFR 233.75-0.18 along with 5 infrared sources, a water maser and the star cluster Mayer 3.

A 1995 paper places Sh 2-299, Sh 2-300, Sh 2-305, Sh 2-306, Sh 2-307 and Sh 2-309 into the same giant molecular cloud complex. A 1996 paper places Sh 2-305 to Sh 2-309 into molecular cloud [JKK96] D within the enormous infrared ring called the GS234-02 supershell, in the Perseus arm.

You can view the enormous dust ring around the supershell in this WISE infrared image. Sh 2-299 and Sh 2-300 also appear in this direction.

Sh 2-306

Coordinates: (234.31°, -0.36°)
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Avedisova lists three ionising O-stars for this nebula, including the hot O5 V star LSS 458. The others are the O9 III giant LSS 499 and the O9.5 III giant LSS 467.

A 1995 paper places Sh 2-299, Sh 2-300, Sh 2-305, Sh 2-306, Sh 2-307 and Sh 2-309 into the same giant molecular cloud complex. A 1996 paper places Sh 2-305 to Sh 2-309 into molecular cloud [JKK96] D within the enormous infrared ring called the GS234-02 supershell, in the Perseus arm.

You can view the enormous dust ring around the supershell in this WISE infrared image. Sh 2-299 and Sh 2-300 also appear in this direction.

A part of the much brighter Sh 2-309 (RCW 13) is visible in the bottom left of this image.

Sh 2-307

Coordinates: (234.56°, 0.83°)
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Avedisova lists the ionising stars as the O9 V BD -18 1920 and the B3 III giant LSS 566. Other sources also include the B0V star MFJ Sh 2-307 3. The nebula contains the infrared cluster candidate [DBS2003] 8.

A 1995 paper places Sh 2-299, Sh 2-300, Sh 2-305, Sh 2-306, Sh 2-307 and Sh 2-309 into the same giant molecular cloud complex. A 1996 paper places Sh 2-305 to Sh 2-309 into molecular cloud [JKK96] D within the enormous infrared ring called the GS234-02 supershell, in the Perseus arm.

You can view the enormous dust ring around the supershell in this WISE infrared image. Sh 2-299 and Sh 2-300 also appear in this direction.

Both Avedisova and a 2007 paper, however, give much closer distance estimates and thus appear to exclude this nebula from the supershell.

You can view a good Dean Salman image of this nebula here.

Sh 2-308

Coordinates: (234.76°, -10.09°)
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This ring nebula surrounds the Wolf-Rayet star WR 6 (EZ CMa), which is one of the closest Wolf-Rayet stars to our solar system and may also partially ionise Sh 2-303 and Sh 2-304.

This distance to WR 6 is a matter of some controversy. The Hipparcos astrometric satellite results were used in 1997 to determine a parallax suggesting a distance of about 575 parsecs. However, other researchers strongly disagreed with this estimate and proposed distances of up to three times this amount.

A revised Hipparcos analysis published in 2007 using the same data determined a very different parallax and a distance of about 1400 pc, much closer to other estimates.

A striking narrow-band image here shows the strong ionised oxygen emission from Sh 2-308, which the photographer calls the Gourd nebula.

Sh 2-309

Coordinates: (234.76°, -0.2°)
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Avedisova concludes that Sh 2-309 is ionised by the star cluster Bochum 6, including the O9 III giant LSS 499. She places it in star formation region SFR 234.76-0.20 along with the HII region Bran 42 and the emission star SS73 6.

The nebula contains the loose infrared cluster [DBS2003] 9.

A 1995 paper places Sh 2-299, Sh 2-300, Sh 2-305, Sh 2-306, Sh 2-307 and Sh 2-309 into the same giant molecular cloud complex. A 1996 paper places Sh 2-305 to Sh 2-309 into molecular cloud [JKK96] D within the enormous infrared ring called the GS234-02 supershell, in the Perseus arm.

You can view the enormous dust ring around the supershell in this WISE infrared image. Sh 2-299 and Sh 2-300 also appear in this direction.

Sh 2-310

Coordinates: (237.25°, -6.5°)
[ See details ]

This vast nebula, one of the largest single HII regions known in the Milky Way, is ionised by two multiple star systems (Tau Canis Majoris and UW Canis Majoris) each made up of several O-class stars. This image shows only the brightest part of the enormous Sh 2-310 complex.

The intense radiation from the Tau Canis Majoris and UW Canis Majoris star systems has created a cavity in the molecular clouds at the centre of Sh 2-310, which is located beyond the upper right of the image.

Avedisova places Sh 2-310 in the star formation region SFR 237.25-6.50 with 62 components, including 4 masers, 14 infrared sources and the dark nebulae LDN 1660 and LDN 1664.

At least one scientific paper notes the "arrow-shaped bright rim" shown in this image. Perhaps Sh 2-310 should be known as the Arrowhead nebula?

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.