High Circular Polarization in the Star Forming Region NGC 6334: Implications

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 homochiraility 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 moelcules. We report here on the detection of high degrees of circular polarization in the star forming complex NGC 6334, in the constellation Scorpius. This important finding suggests the widespread nature of a potentially efficient process to produce biomolecules with large chiral excess, namely selective (asymmetric) photolysis by circularly polarized light. The mechanism, well known in the laboratory, was first suggested to take place in a star forming region by Bailey et al. (1998) following the discovery of high degrees of near-infrared circular polarization 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 polarization, among the small number of sources surveyed so far, lead us to suggest that the conditions needed for selective photolysis by circular polarization to take place may be quite widespread in massive star formation regions.