The Sharpless Catalog

Click on the small images to see larger ones.

Navigate to nebula [ Previous | Next ]

Sh 2-101

Coordinates: (71.6°, 2.8°)
[ See details ]

Avedisova lists 6 ionising stars for the Tulip nebula, including the ultrahot O4 I multiple supergiant HD 190429, the O6.5 III giant HD 227018, and the O9.7 I multiple supergiant HD 226868.

Humphreys places HD 227018 in the Cyg OB3 association. As you can see from this false colour hydrogen-alpha image, the Tulip nebula is located at the edge of the Cyg OB3 association.

The HD 226868 star system is best known because it includes the powerful X-ray source and suspected black hole Cyg X-1.

Available distance estimates place the Tulip nebula and Cyg OB3 in the Orion spur, some distance behind the Cygnus X star formation region.

You can see the setting for the Tulip nebula in this amazing wide angle image.

This MSX image reveals that the Tulip nebula is just a small portion of a much larger nebula visible in infrared.

Sh 2-102

Coordinates: (71.4°, -5.31°)
[ See details ]

The faint red arc of nebulosity is almost lost in the glare of the F5Iab supergiant 41 Cygni.

Avedisova associates Sh 2-102 with the Lynds dark nebula LDN 844 and places them both in the star formation region SFR 71.40-5.31.

Sh 2-103

Coordinates: (74.1°, -8.3°)
[ See details ]

This is the Cygnus Loop supernova remnant, also known as the radio source W78. A small part of this huge 10 thousand year old object is displayed in the image.

You can see an image of the entire object in hydrogen-alpha here and in x-rays here.

Sh 2-104

Coordinates: (74.74°, 0.61°)
[ See details ]

Lahulla identifies two potential ionising stars: the O5 V [L85] S104 4 = [CGG78] S104 Anon 3 and the B0 V [L85] S104 3.

Avedisova gives a slightly cooler O6V class for the main ionising star. She places Sh 2-104 in the star forming region SFR 74.74+0.61 with the star cluster Dolidze 4 and the HII region DWB 14.

You can see a good image of this nebula here. Sh 2-104 is prominent in infrared as can be seen in this MSX 8μm image.

Sh 2-105

Coordinates: (75.45°, 2.43°)
[ See details ]

NGC 6888, the Crescent nebula, is a wind blown bubble originating from the Wolf-Rayet star WR 136.

The Hubble Space Telescope has taken an interesting closeup image of this nebula.

A good image of this nebula is here, and amazing wide field images of the whole region in Cygnus are here and here.

Sh 2-106

Coordinates: (76.39°, -0.63°)
[ See details ]

Despite its appearance, this is not a planetary nebula, but a bipolar nebula embedded in a giant molecular cloud and star formation region ionised by an O8 star, Sh 2-106 IR. Avedisova catalogs this region as SFR 76.38-0.61, with 49 distinct components, including 4 masers.

You can see a radio image of Sh 2-106 here, and a spectacular optical/infrared composite image here.

This MSX infrared image shows that Sh 2-106 is embedded in the tip of a much larger pillar of gas and dust.

Sh 2-107

Coordinates: (77.37°, -3.7°)
[ See details ]

Very little about this tiny and very faint nebula located well below the galactic plane appears in the scientific literature.

Sharpless suggests that Sh 2-107 may be ionised by the B2 class HD 197460. SIMBAD says that this star is actually a B0.5 Ib supergiant and according to this catalog entry, the star has 9.5 +/- 0.2 solar masses and an age of 22.6 +/- 2.7 million years.

Humphreys gives a distance estimate of 2000 parsecs for HD 197460 (and a slightly different class of B1 II(N)). This is at the lower limit of the distance estimate for Sh 2-107 so it is indeed conceivable that this star ionises the nebula.

Sh 2-108

Coordinates: (78.18°, 1.8°)
[ See details ]

Sh 2-108 is sometimes called the Gamma Cygni nebula because of the foreground appearance of the F8Iab supergiant (also called Sadr). In fact this nebula lies far beyond Gamma Cygni in the depths of the Cygnus X complex of star formation regions.

This nebula is also called DWB 63 and is the location of the radio source W66. According to Avedisova, DWB 63 is ionised by Gamma Cygni, the O8 V class HD 229202 and the B2 Ib supergiant HD 193946. Gamma Cygni is now known to be located in the foreground. SIMBAD agrees with the classes for the other two ionising stars.

Avedisova includes Sh 2-108 in star formation region SFR 78.18+1.82 along with the supernova remnant DR4, the infrared star cluster [BDB2003] G077.46+01.76 and numerous other nearby HII regions.

Sh 2-109

Coordinates: (79.48°, 0.15°)
[ See details ]

Sharpless notes "The great size and gross filamentary structure of this nebula set it apart from any known HII region ... Evidently this nebula cannot be considered to be a normal HII region".

When we look in the direction of Sh 2-109 we are looking straight down the Orion spur, the major Milky Way structure that also includes our own solar system.

Sh 2-109 is not a single HII region but rather a complex of many HII regions visible in our line of sight, many of which are ionized by stars in several Cygnus OB associations connected to the Cygnus X complex of star formation regions.

Some of the many nebulae that are part of this region can be seen here.

Sh 2-110

Coordinates: (79.59°, -12.18°)
[ See details ]

This nebula, located far below the galactic plane, lies in the same direction as the high latitude HI shell Hu 8, which consists of about 1300 solar masses of gas, is about 900 thousand years old and lies at a distance of between 350-440 pc.

This IRAS infrared image appears to show a faint bubble in this direction. Sh 2-110 appears as a bright spot at the edge of the bubble.

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.