Located in our galaxy about 5,500 light years from Earth, NGC 6357 is actually a "cluster of clusters," containing at least three clusters of young stars, including many hot, massive, luminous stars. The X-rays from Chandra and ROSAT reveal hundreds of point sources, which are the young stars in NGC 6357, as well as diffuse X-ray emission from hot gas. There are bubbles, or cavities, that have been created by radiation and material blowing away from the surfaces of massive stars, plus supernova explosions.
Fast Facts for NGC 6357:
Scale: Image is about 44 arcmin across (70 light years)
Category: Normal Stars & Star Clusters
Coordinates (J2000): RA 17h 25m 34.2s | Dec -34° 23' 12"
Observation Date: 7 pointings between July 2004 and July 2016
Observation Time: 72 hours 13 min. (3 days 13 min)
Obs. ID: 4477, 10987, 10988, 13267, 13622, 18453
References: Townsley, L. et al, 2014, ApJS, 213, 1; arXiv:1403.2576
Color Code: X-ray (Purple); Optical (Blue); Infrared (Orange)
Distance Estimate: About 5,500 light years