Gum 55
Also called
RCW 113Coordinates: (343.04°, 1.12°)
[ Catalog | Explorer | SIMBAD ]
RCW 113, also called Gum 55, is a huge region of diffuse nebulosity surrounding the Sco OB1 association and its core ionising cluster, NGC 6231.
Gum notes that this region is "A large roughly semicircular loop, whose ragged appearance is due in part to overlying obscuration. At its centre is the galactic cluster NGC 6231, which is the nucleus of an O-Association".
Humphreys lists 3 O-stars and 27 ionising B-class stars in Sco OB1 and gives a distance of 1910 parsecs.
Kharchenko lists 15 ionising stars for NGC 6231 including 9 O-stars, 5 B-stars and the Wolf-Rayet binary star WR 79. The hottest O-star listed by Kharchenko is the O6 III:(f)p binary giant HD 152233. She gives an age of 6.4 million years and a distance of 1250 parsecs for the cluster. A 2008 study gives a distance of 1640 parsecs and finds 15 O-stars in the direction of the cluster core.
You can find a better view of the bat-like edge of this nebula here and a stunning view of the full RCW 113 nebula and the larger Sco OB1 region here.
You can see the full extent of the vast nebular clouds in the Sco OB1 region in this SuperCOSMOS explorer image and some photographs of SFO 82, the prominent bright-rimmed cometary globule visible inside RCW 113, here. SFO 82 is often called "the Dark Tower of Scorpius" by amateur astronomers and is described in detail in this 1976 paper.
Gum notes that this region is "A large roughly semicircular loop, whose ragged appearance is due in part to overlying obscuration. At its centre is the galactic cluster NGC 6231, which is the nucleus of an O-Association".
Humphreys lists 3 O-stars and 27 ionising B-class stars in Sco OB1 and gives a distance of 1910 parsecs.
Kharchenko lists 15 ionising stars for NGC 6231 including 9 O-stars, 5 B-stars and the Wolf-Rayet binary star WR 79. The hottest O-star listed by Kharchenko is the O6 III:(f)p binary giant HD 152233. She gives an age of 6.4 million years and a distance of 1250 parsecs for the cluster. A 2008 study gives a distance of 1640 parsecs and finds 15 O-stars in the direction of the cluster core.
You can find a better view of the bat-like edge of this nebula here and a stunning view of the full RCW 113 nebula and the larger Sco OB1 region here.
You can see the full extent of the vast nebular clouds in the Sco OB1 region in this SuperCOSMOS explorer image and some photographs of SFO 82, the prominent bright-rimmed cometary globule visible inside RCW 113, here. SFO 82 is often called "the Dark Tower of Scorpius" by amateur astronomers and is described in detail in this 1976 paper.
15 O-stars in the direction of the cluster core a distance of 1640 parsecs. [1]
Notes
1. ^ Sana, H., Gosset, E., Nazé, Y., et al. (2008). "The massive star binary fraction in young open clusters - I. NGC 6231 revisited", Monthly Notices of the Royal Astronomical Society, Vol. 386, 447-460. [2008MNRAS.386..447S]
Distance estimates
2000 pc [1996A&AS..120...41G]1640 pc [2008MNRAS.386..447S]
1900 pc +/- 300 [1989BAICz..40...42A]
Links
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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.