NGC 6357

NGC 6357 is a diffuse nebula near NGC 6334 in the constellation Scorpius. The nebula contains many proto-stars shielded by dark disks of gas, and young stars wrapped in expanding "cocoons" or expanding gases surrounding these small stars. It is also known as the Lobster Nebula[4][5] and the Madokami Nebula[6] by some fans of the anime Madoka Magica due to its resemblance to the main character from the anime and a popular fan petition to rename it.

NGC 6357
Emission nebula
H II region
NGC 6357 composite image
Credit: X-ray: NASA/CXC/PSU/L.Townsley et al.; Optical: UKIRT; Infrared: NASA/JPL-Caltech
Observation data: J2000 epoch
Right ascension 17h 24m[1]
Declination−34° 20′[1]
Distance~5900±450[2] ly   (1800±140 pc)
ConstellationScorpius[3]
DesignationsWar and Peace Nebula,[1] Lobster Nebula [4] Sharpless 11, RCW 131, Gum 66

This nebula was also given the name War and Peace Nebula by the Midcourse Space Experiment scientists because of its appearance, which, in infrared images the bright, western part resembles a dove, while the eastern part looks like a skull.[7]

It is located about 5500 light years away from Earth.[8]

Associated Open Clusters

Pismis 24
A Hubble Space Telescope (HST) image of Pismis 24-1, the "core" of NGC 6357.

This nebula includes the open cluster Pismis 24, which is home to several massive stars. One of the brightest stars in the cluster, Pismis 24-1, was thought possibly to be the most massive on record, approaching 300 solar masses, until it was discovered to be a multiple system of at least three stars; component stars would still remain near 100 solar masses each, making them among the more massive stars on record.[9][10]

G353.2+0.7

The young stellar cluster G353.2+0.7 lies east of Pismis 24 and was revealed by a Chandra X-ray image showing approximately 800 stars.[11]

G353.1+0.6

The young stellar cluster G353.1+0.6 lies southeast of Pismis 24 and also contains approximately 800 stars detected by X-ray.[11] The region includes several O-type stars, including [BDSB2003] 10.[12]

Massive stars

NGC 6357 is one of the most prominent sites of massive-star formation our neighborhood of the Milky Way. A variety of early O-type stars reside in this nebula, blowing the bubbles around the stars clusters that can be seen in the molecular cloud.

Prominent stars in Pismis 24[13]
Star
(Pismis 24-#)		 Spectral type Magnitude
(Mbol)		 Temperature[14]
(K)		 Radius
(R☉)		 Mass
(M☉)
1NEO3.5 If*−10.042,0001774
1SWO4 III−9.841,5001666
2O5.5 V(f)−8.940,0001243
3O8 V−7.733,400925
10O9 V−7.231,500820
12B1 V−5.330,000411
13O6.5 III((f))−8.635,6001235
15O8 V−7.833,4001025
16O7.5 V−9.034,0001638
17O3.5 III−10.142,7001778
18B0.5 V−6.430,000615
19B0.5 V−5.430,000411

References
  1. "NGC 6357". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2007-05-03.
  2. Kuhn, Michael A.; Hillenbrand, Lynne A.; Sills, Alison; Feigelson, Eric D.; Getman, Konstantin V. (2018). "Kinematics in Young Star Clusters and Associations with Gaia DR2". The Astrophysical Journal. 870 (1): 32. arXiv:1807.02115. Bibcode:2019ApJ...870...32K. doi:10.3847/1538-4357/aaef8c.
  3. R. W. Sinnott, ed. (1988). The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J. L. E. Dreyer. Sky Publishing Corporation and Cambridge University Press. ISBN 978-0-933346-51-2.
  4. Sample, Ian (20 February 2013). "Lobster Nebula – birthplace of stars – revealed in infrared". the Guardian.
  5. "Lobster Nebula Seen with ESO's VISTA Telescope Space Wallpaper".
  6. "Star Observatory Spots Ultimate Madoka in Space".
  7. "2MASS Picture of the Week Archive Captions".
  8. "Winter Wonderland' Glows in Space as Nebula Is Wreathed in Wintry Colors". Space.com.
  9. "ESA Science & Technology: Star on a Hubble diet NGC 6357". Archived from the original on 2007-04-04. Retrieved 2007-04-11.
  10. Nemiroff, R.; Bonnell, J., eds. (19 December 2006). "NASA: Massive Stars in Open Cluster Pismis 24". Astronomy Picture of the Day. NASA.
  11. Townsley, L. K.; et al. (2014). "The Massive Star-Forming Regions Omnibus X-Ray Catalog". Astrophysical Journal Supplement. 213 (1): 1. arXiv:1403.2576. Bibcode:2014ApJS..213....1T. doi:10.1088/0067-0049/213/1/1.
  12. Damke, G.; et al. (2006). "The open cluster G353.1+0.7 in NGC6357". Revista Mexicana de Astronomía y Astrofísica. 26: 180. Bibcode:2006RMxAC..26..180D.
  13. Fang, M.; Van Boekel, R.; King, R. R.; Henning, T.; Bouwman, J.; Doi, Y.; Okamoto, Y. K.; Roccatagliata, V.; Sicilia-Aguilar, A. (2012). "Star formation and disk properties in Pismis 24". Astronomy & Astrophysics. 539: A119. arXiv:1201.0833. Bibcode:2012A&A...539A.119F. doi:10.1051/0004-6361/201015914.
  14. Martins, F.; Schaerer, D.; Hillier, D. J. (2005). "A new calibration of stellar parameters of Galactic O stars". Astronomy and Astrophysics. 436 (3): 1049–1065. arXiv:astro-ph/0503346. Bibcode:2005A&A...436.1049M. doi:10.1051/0004-6361:20042386.
  1. Star Forming Region NGC 6357 showing complex interactions between interstellar winds, radiation pressures and magnetic fields.
  2. A Massive Star in NGC 6357 with a close-up of Pismis 24.
  3. NGC 6357: Cathedral to Massive Stars
  4. A Massive Star in NGC 6357
  5. NGC 6357: Cathedral to Massive Stars
  6. NGC 6357: The Lobster Nebula
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