... Massive Stars in Open Cluster Pismis 24 . ... Estimates made from distance, brightness and standard solar models had given one star in the open cluster Pismis 24 over 200 times the mass of our Sun, making it a record holder. ... Toward the bottom of the image, stars are still forming in the associated emission nebula NGC 6357 , including several that appear to be breaking out and illuminating a spectacular cocoon . ... Publications with keywords: massive stars - star formation . ...