RCW 147
Also called
Sh 2-30, Gum 76Coordinates: (7.0°, -0.2°)
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The Trifid nebula is usually assumed to be part of the Sgr OB1 association in the Sagittarius arm, along with the Lagoon nebula. However, the surprisingly large range of distance estimates for the nebula leaves open the possibility that it lies much further away in the Centaurus arm.
A Chandra X-ray study finds 304 X-ray sources and gives an age estimate of only 300 thousand years. [1]
SIMBAD gives a class of O6 for HD 164492 but a 2011 paper gives a O7.5 class for this star. [2]
There is a surprising range of distance estimates for the Trifid nebula.
Analysis based on the velocity of gas measured in the Trifid direction using radio telescopes suggests that the Trifid nebula lies at a distance of 3010 parsecs. [3]
A visual examination of the A component of HD 164492 suggests a distance of 1680 parsecs. [4]
Including the other B-F components of HD 164492 suggests a distance of between 2500 to 2800 parsecs according to a 1999 paper [5] and this uncertainty range is extended by a 2011 paper examining the dust extinction observed towards the nebula and concluding a distance range of 2700 +/- 500 parsecs. [6]
But a study of NGC 6514, the star cluster that includes HD 164492, concludes that the Trifid nebula is much closer than any of these other estimates - only 816 parsecs away. [7]
Notes
1. ^ Rho, Jeonghee, Ramírez, Solange V., Corcoran, Michael F., et al. (2004). "Chandra Observation of the Trifid Nebula: X-Ray Emission from the O Star Complex and Actively Forming Pre-Main-Sequence Stars", The Astrophysical Journal, Vol. 607, 904-912. [2004ApJ...607..904R]
2. ^ Torii, K., Enokiya, R., Sano, H., et al. (2011). "Molecular Clouds in the Trifid Nebula M20: Possible Evidence for a Cloud-Cloud Collision in Triggering the Formation of the First Generation Stars", The Astrophysical Journal, Vol. 738, 46. [2011ApJ...738...46T]
3. ^ Paladini, R., Burigana, C., Davies, R. D., et al. (2003). "A radio catalog of Galactic HII regions for applications from decimeter to millimeter wavelengths", Astronomy and Astrophysics, Vol. 397, 213-226. [2003A&A...397..213P]
4. ^ Lynds, B. T., Canzian, B. J., & Oneil, E. J., Jr. (1985). "Optical measurements of the Trifid dust", The Astrophysical Journal, Vol. 288, 164-169. [1985ApJ...288..164L]
5. ^ Kohoutek, L., Mayer, P., & Lorenz, R. (1999). "Photometry and spectroscopy of the central star of the Trifid nebula", Astronomy and Astrophysics Supplement Series, Vol. 134, 129-133. [1999A&AS..134..129K]
6. ^ Cambrésy, L., Rho, J., Marshall, D. J., et al. (2011). "Variation of the extinction law in the Trifid nebula", Astronomy and Astrophysics, Vol. 527, A141. [2011A&A...527A.141C]
7. ^ Kharchenko, N. V., Piskunov, A. E., Röser, S., et al. (2005). "Astrophysical parameters of Galactic open clusters", Astronomy and Astrophysics, Vol. 438, 1163-1173. [2005A&A...438.1163K]
Distance estimates
3010 pc [2003A&A...397..213P]1680 pc [1985ApJ...288..164L]
816 pc [2005A&A...438.1163K]
2700 pc +/- 500 [2011A&A...527A.141C]
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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.