Star cluster Pismis 24 (upper centre) above the nebula NGC 6357, Hubble Space Telescope image. The nebula is glowing under the impact of radiation from hot, young stars, such as those in the cluster. The largest and brightest member of the cluster, at upper centre, is Pismis 241. It was thought to be over 150 solar masses, beyond the theoretical limit for star formation, but a Hubble image has revealed it to be two massive stars, not one. See image R670210. This region of the sky is 8000 light years from Earth, in the constellation Scorpius. This image was obtained with Hubbles Wide Field Planetary Camera 2 instrument. The results were published in December 2006.