Gum 74a
Also called
RCW 145, Sh 2-28Coordinates: (6.6°, 0.1°)
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This large faint HII region next to the Trifid nebula is ionised by the O9Ib supergiant LS 4551 and the O-class LS 4538, It lies in the direction of the supernova remnant SNR G006.4-00.1 (W 28).
You can view a SuperCOSMOS hydrogen-alpha image.
You can view a SuperCOSMOS hydrogen-alpha image.
Sh 2-28 and RCW 145 are the same object. This becomes clear by comparing the direction and size of RCW 145 with the corrected BFS coordinates for Sh 2-28. For more information on errors in the original Sharpless catalog, see this article.
Unfortunately SIMBAD uses the incorrect original Sharpless coordinates for Sh 2-28 rather than the corrected BFS coordinates.
Perhaps because of the errors in the original Sharpless coordinates for Sh 2-28, the RCW catalog identifies RCW 145 and Sh 2-26. Sh 2-26 is a smaller even fainter nebula further from the galactic plane (although part of it does appear to intersect the top of the boundaries the RCW catalog gives for RCW 145.).
The W 28 supernova remnant appears to be further away at a distance of 1800 to 3300 pc [1] but, on the other hand, a 1978 paper by Crampton and Georgelins concludes that the nebula is the optical equivalent of W 28 and includes the supernova remnant. It appears to be associated with M 20, the Trifid nebula. Crampton and Georgelins conclude that Sh 2-28 is ionised by LSS 4551 and LSS 4538. [2]
A 1993 paper finds a distance of 1500 pc for LS 4551. [3]
Unfortunately SIMBAD uses the incorrect original Sharpless coordinates for Sh 2-28 rather than the corrected BFS coordinates.
Perhaps because of the errors in the original Sharpless coordinates for Sh 2-28, the RCW catalog identifies RCW 145 and Sh 2-26. Sh 2-26 is a smaller even fainter nebula further from the galactic plane (although part of it does appear to intersect the top of the boundaries the RCW catalog gives for RCW 145.).
The W 28 supernova remnant appears to be further away at a distance of 1800 to 3300 pc [1] but, on the other hand, a 1978 paper by Crampton and Georgelins concludes that the nebula is the optical equivalent of W 28 and includes the supernova remnant. It appears to be associated with M 20, the Trifid nebula. Crampton and Georgelins conclude that Sh 2-28 is ionised by LSS 4551 and LSS 4538. [2]
A 1993 paper finds a distance of 1500 pc for LS 4551. [3]
Notes
1. ^ Giuliani, A., Tavani, M., Bulgarelli, A., et al. (2010). "AGILE detection of GeV γ-ray emission from the SNR W28", Astronomy and Astrophysics, Vol. 516, L11. [2010A&A...516L..11G]
2. ^ Crampton, D., Georgelin, Y. M., & Georgelin, Y. P. (1978). "First optical detection of W51 and observations of new H II regions and exciting stars", Astronomy and Astrophysics, Vol. 66, 1-11. [1978A&A....66....1C]
3. ^ Kilkenny, D. (1993). "A study of reddened luminous stars in the Southern Milky Way. II. Hβ photometry, reddening and distances.", South African Astronomical Observatory Circular, Vol. 15, 53-64. [1993SAAOC..15...53K]
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Most of the sources used to create these nebula descriptions are listed in the
notes section for each description. In some cases,
for example the Avedisova, Humphreys and Reed catalogs, the source is used extensively and is not listed in the
individual nebula descriptions. See this catalog overview
for more information on the catalogs and the general sources used
to create these descriptions and this introduction to HII regions
on the general history of this area of astronomy.
This image was 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.