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Post Info TOPIC: NGC 6357


L

Posts: 131433
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Gum 66
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Celestial Cat Meets Cosmic Lobster

Astronomers have for a long time studied the glowing, cosmic clouds of gas and dust catalogued as NGC 6334 and NGC 6357, this gigantic new image from ESO's Very Large Telescope Survey Telescope being only the most recent one. With around two billion pixels this is one of the largest images ever released by ESO. The evocative shapes of the clouds have led to their memorable names: the Cat's Paw Nebula and the Lobster Nebula, respectively.
NGC 6334 is located about 5500 light-years away from Earth, while NGC 6357 is more remote, at a distance of 8000 light-years. Both are in the constellation of Scorpius (The Scorpion), near the tip of its stinging tail.

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RE: NGC 6357
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Title: Young open clusters in the galactic star forming region NGC 6357
Author: Fabrizio Massi (1), Andrea Giannetti (2 and 5), Elisa di Carlo (3), Jan Brand (2 and 5), Maria Teresa Beltrán (1), Gianni Marconi (4) ((1) INAF - OA Arcetri, (2) INAF - IRA Bologna, (3) INAF - OA Teramo, (4) ESO - Chile, (5) Italian ALMA Regional Centre)

NGC6357 is an active star forming region with very young massive open clusters (OC). These clusters contain some of the most massive stars in the Galaxy and strongly interact with nearby giant molecular clouds (GMC). We study the young stellar populations of the region and of the OC Pismis24, focusing on their relationship with the nearby GMCs. We seek evidence of triggered star formation propagating from the clusters. We used new deep JHKs photometry, along with unpublished deep IRAC/Spitzer MIR photometry, complemented with optical HST/WFPC2 high spatial resolution photometry and X-ray Chandra observations, to constrain age, initial mass function, and star formation modes in progress. We carefully examine and discuss all sources of bias (saturation, confusion, different sensitivities, extinction). NGC6357 hosts three large young stellar clusters, of which Pismis24 is the most prominent. We found that Pismis24 is a very young (~1-3 Myr) OC with a Salpeter-like IMF and a few thousand members. A comparison between optical and IR photometry indicates that the fraction of members with a NIR excess (i. e., with a circumstellar disk) is in the range 0.3-0.6, consistent with its photometrically derived age. We also find that Pismis24 is likely subdivided into a few different sub-clusters, one of which contains almost all the massive members. There are indications of current star formation triggered by these massive stars, but clear age trends could not be derived (although the fraction of stars with a NIR excess does increase towards the HII region associated with the cluster). The gas out of which Pismis24 formed must have been distributed in dense clumps within a cloud of less dense gas ~1 pc in radius. Our findings provide some new insight into how young stellar populations and massive stars emerge, and evolve in the first few Myr after birth, from a giant molecular cloud complex.

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Panning across the stellar nursery NGC 6357



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NGC 6357 (also War and Peace Nebula, Lobster Nebula, Sharpless 11, RCW 131, Gum 66 and ESO 392-SC10) is a magnitude +8.2 emission nebula located 8000 light-years away in the constellation Scorpius.
The nebula includes the open cluster Pismis 24, which is home to some of the most massive stars known.

The nebula was discovered by British astronomer John Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflecting telescope at the Cape of Good Hope on the 8th June 1837. 

Right Ascension 17h 24m 43.5s, Declination -34° 12' 05"



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