A POINT IN FAVOR OF THE SUPERPARAMAGNETIC GRAIN HYPOTHESIS

If the GEMS (glass with embedded metal and sulfides) particles recentl y identified by meteoriticists are indeed examples of interstellar sil icate grains, then the spacing of the embedded ''superparamagnetic'' ( SPM) inclusions in GEMS particles appears consistent with the theory o f superparamagnetic grain alignment first proposed by Jones & Spitzer. Using an SPM hypothesis, Mathis has shown that the observed wavelengt h dependence of the polarization of background starlight is readily ex plained if grains smaller than about 0.09 mu m in size have no SPM inc lusions. Martin has already noted that the bulk properties of GEMS par ticles are consistent with the SPM hypothesis, as well as with the not ion that GEMS particles are interstellar grains. In this Letter we mak e the single point that the spatial frequency (similar to 0.1 mu m) of the SPM inclusions implied by the GEMS particles for interstellar gra ins is tantalizingly close to the Mathis value needed to explain the o bserved wavelength dependence of polarization.