Star Crossed Postcard

How massive can a star be? Estimates made from distance, brightness and standard solar models have accorded one star in the open cluster Pismis 24 over 200 times the mass of our sun. This star is the brightest object located just to the right of the gas front in the above image. Close inspection of images taken recently with the Hubble Space Telescope, however, have shown that Pismis 24-1 derives its brilliant luminosity not from a single star but from three at least. Component stars would still remain near 100 solar masses, making them among the more massive stars currently on record. Towards the image left, stars are still forming in the associated emission nebula NGC 6357, including several that appear to be breaking out and illuminating a spectacular cocoon. Image credit: NASA, ESA and J. M. Apellániz (IAA, Spain)