A fascinating part of NGC 6357 is the open star cluster at it's core - Pismis 24 (above the bright area below centre frame). It was once thought to contain a star (Pismis 24-1) with 200 to 300 times the mass of our Sun, making it one of the most massive stars known. It turns out that it's actually 2 stars separated by only 500AU (less than 3 light days) with a combined mass of a mere 140 suns (Pismis 24-1 NE and SW). These stars appear as the single brightest star in the cluster located just above the bright gas front below centre in the frame. For a list of massive stars making up the Pismis 24 cluster see https://pbase.com/gailmarc/image/170843222/original.