RCW 161
Coordinates: (16.1°, -0.3°)
[ Catalog | Explorer | SIMBAD ]
RCW 161 is a large faint region of diffuse nebulosity located between the Eagle and Omega nebulae. It appears to form a connecting link between these much brighter HII regions. RCW 161, like the Eagle and Omega nebulae, appears to be ionised by members of the Ser OB1 association.
It is not clear that RCW 161 is a single object as the ionising stars in this direction appear to be spread across several hundred parsecs.
It is not clear that RCW 161 is a single object as the ionising stars in this direction appear to be spread across several hundred parsecs.
The RCW catalog lists this as a large 80x40 arcminute medium bright nebula and associates it with the HII region [GS55] 143.
Winkler associates RCW 161 with the variable B5I supergiant HD 167838 at a distance of 1620 parsecs. [1] SIMBAD gives a warmer B3I class for this star.
Reed lists four ionising stars in this direction: LS 4936 (B2.5 Ib), LS 4929 (O9.5/B0 IAB), LS 4930 (O6) and LS 4923 (O9.5 III). According to Humphreys, LS 4930 = BD-15 4930 is a member of the Ser OB1 association. She gives a distance estimate of 1910 parsecs for Ser OB1. A 2000 paper gives a distance estimate of 2200 parsecs for the star itself. [2]
Avedisova divides this nebulosity into three separate star formation regions. These can be seen in this SuperCOSMOS hydrogen-alpha image. The easternmost of these regions (in galactic coordinates), SFR 16.35-0.16, contains the Lockman compact radio HII region [L89b] 16.313-0.162 and is visible in infrared as can be seen in this MSX infrared image. The more detailed Spitzer image suggests that this region may consist of several objects. A 2009 paper gives a distance estimate of 4100 parsecs for [L89b] 16.313-0.162 suggesting that this region likely lies far behind RCW 161.
The Ser OB1 association can be seen in this labelled false-colour hydrogen-alpha image.
Winkler associates RCW 161 with the variable B5I supergiant HD 167838 at a distance of 1620 parsecs. [1] SIMBAD gives a warmer B3I class for this star.
Reed lists four ionising stars in this direction: LS 4936 (B2.5 Ib), LS 4929 (O9.5/B0 IAB), LS 4930 (O6) and LS 4923 (O9.5 III). According to Humphreys, LS 4930 = BD-15 4930 is a member of the Ser OB1 association. She gives a distance estimate of 1910 parsecs for Ser OB1. A 2000 paper gives a distance estimate of 2200 parsecs for the star itself. [2]
Avedisova divides this nebulosity into three separate star formation regions. These can be seen in this SuperCOSMOS hydrogen-alpha image. The easternmost of these regions (in galactic coordinates), SFR 16.35-0.16, contains the Lockman compact radio HII region [L89b] 16.313-0.162 and is visible in infrared as can be seen in this MSX infrared image. The more detailed Spitzer image suggests that this region may consist of several objects. A 2009 paper gives a distance estimate of 4100 parsecs for [L89b] 16.313-0.162 suggesting that this region likely lies far behind RCW 161.
The Ser OB1 association can be seen in this labelled false-colour hydrogen-alpha image.
Notes
1. ^ Winkler, H. (1997). "Red and infrared colours of B stars and the reddening law in the Galaxy", Monthly Notices of the Royal Astronomical Society, Vol. 287, 481-494. [1997MNRAS.287..481W]
2. ^ Callaway, Matthew B., Savage, Blair D., Benjamin, Robert A., et al. (2000). "Observational Evidence of Supershell Blowout in GS 018-04+44: The Scutum Supershell", The Astrophysical Journal, Vol. 532, 943-969. [2000ApJ...532..943C]
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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.