The Sharpless Catalog

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Sh 2-51

Coordinates: (16.97°, -5.18°)
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There is an extremely faint diagonal band of nebulosity at this location, which is far below the galactic plane. SIMBAD says that this nebula is also LBN 65.

This region is more easily visible in hydrogen-alpha. Sh 2-51 appears to be connected to the lower edge of the blowout ejected from a huge structure of 620 thousand solar masses of gas and dust in the inner galaxy called the Scutum Supershell.

Sh 2-52

Coordinates: (17.5°, -22.2°)
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The faint blue glow comes from the planetary nebula also known as Abell 65. It is highly unusual for a planetary nebula because it contains an eclipsing binary central star. See Sh 2-313 for another example of such a blue planetary nebula with a binary central star.

Sh 2-53

Coordinates: (18.2°, -0.3°)
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Sharpless notes that Sh 2-53 consists of "About six detached portions". The area is prominent at both radio and infrared frequencies.

Avedisova places the nebula in the complex star formation region SFR 18.18-0.30, which includes 4 molecular clouds, a methanol maser and at least 4 additional HII regions visible at radio and infrared frequencies.

You can view a good black and white hydrogen-alpha image here.

Sh 2-54

Coordinates: (18.7°, 2.0°)
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This HII region is ionised by the young NGC 6604 star cluster, which includes the O5-8V+O5-8V+O8I supergiant multiple HD 167971 and the radio source W 35. It lies, unusually, about 70 parsecs above the galactic plane within the Ser OB2 association.

Ser OB2 contains over 100 OB stars with a common age of about 5 million years.

A good image of this nebula, which looks like a nest (Gum 84) carrying a tiny egg (Gum 85), can be seen here.

Sh 2-55

Coordinates: (20.29°, -1.14°)
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This tiny HII region, also called LBN 73, may be part of the Scutum supershell. Sharpless concludes that it is ionised by BD -11 4665. Neither Sharpless nor SIMBAD give a class for this star. The dark nebula immediately below Sh 2-55 is LDN 412.

Sh 2-55 is near a large nebular region in hydrogen-alpha that appears to mark the main boundary of the Scutum Supershell.

Sh 2-56

Coordinates: (21.97°, 0.06°)
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This HII region is visible in infrared as the luminous water maser GAL 021.88+00.02.

Sh 2-57

Coordinates: (22.89°, 0.68°)
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The tiny nebula Sh 2-57 is ionised by the B0.5 III giant BD -8 4623 within the Sct OB2 association in the Sagittarius arm.

Sh 2-58

Coordinates: (23.1°, 0.6°)
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No ionising star has been identified in the scientific literature for Sh 2-58, which is prominent in infrared as the bubble [CPA2006] N30 as well as in radio.

Avedisova includes Sh 2-58 in the star formation region SFR 23.13+0.55, along with the molecular cloud SYCSW 317 and the compact radio HII region [L89b] 23.115+0.556.

Sh 2-57 and Sh 2-58 are visible together in the sky (as shown by this hydrogen-alpha image), divided by the dark nebula LDN 446 and just east of the Scutum Supershell. However, they seem to be located at quite different distances, with Sh 2-58 at about the same distance as the Supershell and Sh 2-57 in front of this region.

Sh 2-59

Coordinates: (24.5°, -0.2°)
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No significant references appear in the scientific literature for this nebula, which lies in the approximate direction of the star cluster NGC 6664 and can be seen in hydrogen-alpha as the brightest portion of a much larger nebula at the edge of the Sct OB2 association. The hottest star in the direction of this diffuse nebula is the O6 class HD 172275.

Sh 2-60

Coordinates: (25.3°, 0.21°)
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This large nebula is most often named GAL 025.4-00.2 or GAL 025.38-00.18 in the scientific literature. It has a bewildering number of different names in SIMBAD (not all cross-referenced).

It may be associated with the radio source W 42.

It is visible in infrared as the prominent bubble [CPA2006] N37 and appears to be ionised by an obscured O7 II giant.

The radio source W 42 has wildly varying distance estimates (from 13400 parsecs to 2200 parsecs). If the near estimate of 2200 parsecs (which is from a recent paper published in 2000) is accepted, then W 42 is likely part of the Sh 2-60 nebula. Infrared imagery in the same paper shows that W 42 is energised by a massive, dense and young OB star cluster embedded in an obscuring dust cloud in the bottom left part of this image.

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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.