Astronomical sources of circularly polarized light and the origin of homochirality.

Possible astronomical sources of ultraviolet circularly polarized light (UVCPL) which might be responsible for enantiomeric selection in interstellar organic molecules are considered, Synchrotron radiation from magnetic neutron stars has been suggested as a possible source of UVCPL. However, synchrotron radiation in these situations is not predicted to be strongly circularly polarized. Very few such sources show optical synchrotron radiation and in the few that do circular polarization has not been observed. Magnetic white dwarfs and white dwarf binaries (Polars) can be highly circularly polarized but any effect on molecular clouds and star formation regions must rely on rare chance encounters. Recent observations show that substantial levels of circular polarization are present in reflection nebulae in star formation regions. This mechanism produces polarized light exactly when and where it is needed in regions where star formation is occurring and organic molecules are known to be present.