High Circular Polarisation in the Star Forming RegionNGC 6334 :

The amino-acids which form the building blocks of biological proteins are all left-handed molecules. By contrast, when these molecules are made in the laboratory equal numbers of the right and left-handed versions are made. This homochirality found in biological material may well be a prerequisite for the origin of life and a number of processes have been proposed to produce the required enantiomeric excess in prebiotic organic molecules. We report here on the detection of high degrees of circular polarisation in the star forming complex NGC 6334, in the constellation Scorpius. This important nding suggests the widespread nature of a potentially eecient process to produce biomolecules with large chiral excess, namely selective (asymmetric) photolysis by circularly polarised light. The mechanism, well known in the laboratory, was rst suggested to take place in a star forming region by Bailey et al. (1998) following the discovery of high degrees of near-infrared circular polarisation in the Orion molecular cloud, OMC-1. NGC 6334 is a giant HII region and molecular cloud similar to Orion. These two detections of large circular polarisation, among the small number of sources surveyed so far, lead us to suggest that the conditions needed for selective photolysis by circular polarisation to take place may be quite widespread in massive star formation regions.