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| NGC 6357 | |
|---|---|
| Name | NGC 6357 |
| Type | Emission nebula |
| Constellation | Scorpius |
| Epoch | J2000 |
| Distance | ~5,500 ly |
| Other names | War and Peace Nebula, Lobster Nebula |
NGC 6357 is a large emission nebula complex in Scorpius associated with massive star formation, rich ionized gas, and young stellar clusters. It lies in the southern Milky Way near the Galactic plane and is notable for containing several compact clusters, bright H II regions, and multiple O-type stars that influence surrounding molecular clouds. The complex has been studied across wavelengths by observatories and surveys dedicated to Galactic structure and star formation.
The complex occupies a field surveyed by instruments from Palomar Observatory and European Southern Observatory programs to Chandra X-ray Observatory campaigns and Hubble Space Telescope imaging, linking multiwavelength datasets from radio arrays such as the Very Large Array to infrared surveys like Spitzer Space Telescope observations and Two Micron All Sky Survey. Astronomers compare the region to other massive-star nurseries such as Orion Nebula, Carina Nebula, and Westerlund 2 to probe feedback processes, and it appears in catalogs compiled by the New General Catalogue and targeted by surveys led by institutions like the Max Planck Society and Harvard–Smithsonian Center for Astrophysics.
The complex contains multiple subregions mapped by instruments operated by agencies including NASA, European Space Agency, and national observatories in Chile and South Africa. Key structural elements include extended H II regions, dark molecular lanes mapped by facilities like the Atacama Large Millimeter/submillimeter Array, and bubble-like shells resembling structures seen in Rosette Nebula studies and models from the Royal Astronomical Society. Embedded clusters are cataloged through programs at European Southern Observatory campuses and university groups at University of Cambridge, Massachusetts Institute of Technology, and University of California, Berkeley.
Star formation in the complex is driven by massive stars comparable to those in Trumpler 14 and NGC 3603, with populations characterized through spectroscopy at Keck Observatory and photometry from Hubble Space Telescope programs. Surveys by teams at Space Telescope Science Institute and the Max Planck Institute for Astronomy identified numerous O-type and B-type stars, pre-main-sequence objects, and candidate protostars similar to objects in Rho Ophiuchi and NGC 2244. Stellar feedback, photoionization, and triggered star formation mechanisms are analyzed using theoretical frameworks developed at institutions such as Princeton University and California Institute of Technology.
The nebula exhibits emission-line spectra dominated by recombination and forbidden lines studied with spectrographs on Very Large Telescope and Subaru Telescope, with diagnostics developed by research groups at University of Chicago and Columbia University. Emission from hydrogen, helium, oxygen, nitrogen, and sulfur yields physical conditions constrained by methods from the Royal Society-affiliated literature and comparative analyses with the chemical enrichment patterns observed in NGC 346 and 30 Doradus. Infrared emission tracing dust and polycyclic aromatic hydrocarbons has been mapped by Spitzer Space Telescope teams collaborating with researchers at Jet Propulsion Laboratory.
Distance estimates employ techniques refined by consortia at European Southern Observatory and Gaia mission teams, placing the complex at several thousand light-years from the Sun, with physical size and mass inferred through radio and submillimeter mapping by Atacama Large Millimeter/submillimeter Array and James Clerk Maxwell Telescope surveys. The region's ionizing photon budget ties to O-star content measured in programs run by National Radio Astronomy Observatory and stellar evolutionary models from Geneva Observatory groups. Thermal and nonthermal emission components are compared to results from studies of Cygnus X and Scutum–Centaurus Arm star-forming complexes.
The complex appears in early photographic sky surveys compiled by astronomers associated with the Royal Observatory, Greenwich and the compilers of the New General Catalogue. Later detailed investigations were carried out by teams at Palomar Observatory and through radio surveys by the National Radio Astronomy Observatory. Modern X-ray and infrared exploration was driven by projects at Chandra X-ray Observatory, Spitzer Space Telescope, and the European Southern Observatory, while subsequent spectroscopic follow-up used facilities at Keck Observatory and Very Large Telescope.
Prominent embedded clusters and massive stars within the complex are targets of study by researchers at institutions including Harvard University, University of Cambridge, and Max Planck Institute for Radio Astronomy. Compact H II regions and candidate young stellar objects are cataloged in surveys coordinated with Space Telescope Science Institute and the Sloan Digital Sky Survey. The region hosts high-mass protostars analogous to sources in Mon R2 and compact objects investigated in comparisons to Eta Carinae studies, making it a focus for teams at California Institute of Technology and University of Colorado Boulder.
Category:Emission nebulae