The Sharpless Catalog

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Sh 2-21

Also: RCW 142
Coordinates: ( 0.59°, -0.86°)
Distance: 8000 pc, Size: 11.6 pc
Source: 2003A&A...397..133R

[ Find on map | See details ] 		Sh 2-21

This HII region is located near the galactic nucleus and is associated with a giant molecular cloud and two star clusters.

Sh 2-22

Also: RCW 144, Gum 71
Coordinates: ( 4.28°, 0.55°)
Distance: 1200 pc, Size: 20.9 pc
Source: 1982ApJS...49..183B

[ Find on map | See details ] 		Sh 2-22

This is a ring nebula surrounding the O-star HD 162978.

Sh 2-23

Coordinates: ( 4.32°, 29.60°)
Distance: 200 pc, Size: 2.9 pc
Source: 2003A&A...397..133R

[ Find on map | See details ] 		Sh 2-23

Close to the A4V star 16 Sco

Sh 2-24

Coordinates: ( 5.10°, 30.85°)
Distance: 145 pc, Size: 1.3 pc
Source: 1993ApJS...88..433P

[ Find on map | See details ] 		Sh 2-24

The eerie blue glow of MBM 57 is at a distance stretching between 50 and 240 pc, making it one of the closest known molecular clouds.

Sh 2-25

Also: RCW 146, Gum 72
Coordinates: ( 6.09°, -1.29°)
Distance: 1250 pc, Size: 32.7 pc
Source: 2005A&A...430..941P

[ Find on map | See details ] 		Sh 2-25

The Lagoon nebula (M8 = NGC 6523-NGC 6530) is a large HII region mainly ionized by two O-class stars, 9 Sagitarii [O4V((f))] and HD 165052 (O6.5V + O7.5V). It is embedded within a molecular cloud which extends to the star cluster NGC 6530. Within M8’s core lies a distinctive bipolar nebula called the Hourglass, a blister-type HII region which has been produced by the O7.5V star Herschel 36 (Her 36).

Note that RCW 146 also includes Gum 75 (Sh 2-29, Sh 2-31, and Sh 2-32), the nebula complex next to the Lagoon nebula. See this web page for more details about this region.

Sh 2-26

Coordinates: ( 6.19°, 0.35°)
Distance: 2500 pc, Size: 14.5 pc
Source: 2003A&A...397..133R

[ Find on map | See details ] 		Sh 2-26

This is part of the large region of nebulosity west of the Trifid nebula that includes RCW 145.

Sh 2-27

Also: Gum 73
Coordinates: ( 6.28°, 23.59°)
Distance: 170 pc, Size: 23.8 pc
Source: 1982ApJS...49..183B

[ Find on map | See details ] 		Sh 2-27

This is an extended HII region around the O-class star Zeta Ophiuchi.

Sh 2-28

Coordinates: ( 6.60°, -0.60°)
Distance: 2500 pc, Size: 29.1 pc
Source: 2003A&A...397..133R

[ Find on map | See details ] 		Sh 2-28

This is the optical equivalent of W28 and includes a supernova remnant. It appears to be associated with M20, the Trifid nebula.

Sh 2-29

Also: RCW 146, Gum 75
Coordinates: ( 7.00°, -2.16°)
Distance: 1300 pc, Size: 15.1 pc
Source: 1982ApJS...49..183B

[ Find on map | See details ] 		Sh 2-29

In 2003, an infrared cluster was reported in NGC 6559, which is part of Sh 2-29. Sh 2-29, Sh 2-31, and Sh 2-32 all appear to be part of the same nebula complex although the associated CO velocities suggest that these objects may have quite different distances.

Sh 2-30

Also: RCW 147, Gum 76
Coordinates: ( 7.00°, -0.20°)
Distance: 3010 pc, Size: 4.9 pc
Source: 2003A&A...397..213P

[ Find on map | See details ] 		Sh 2-30

The Trifid nebula, M20, is an HII region ionised by the O7.5 star HD 164492A and is divided into three parts by dust lanes. A blue reflection nebula surrounds the HII region and also appears just to the north. It is only 300 thousand years old.

A Chandra X-ray study found 304 X-ray sources.


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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 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.

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.