Dust-Scattered Ultraviolet Halos around Bright Stars

Abstract: We have discovered ultraviolet halos extending as far as 5{\deg} around four (of six) bright UV stars using data from the GALEX satellite. These halos are due to the scattering of the starlight from nearby thin, foreground dust clouds. We have placed limits of 0.58 $\pm$ 0.12 and 0.72 $\pm$ 0.06 on the phase function asymmetry factor (g) and limits on the albedo of 0.10 $\pm$ 0.05 and 0.26 $\pm$ 0.10 in the FUV (1521 {\AA}) and NUV (2320 {\AA}) bands, respectively. We suggest that these halos are a common feature around bright stars and may be used to explore the scattering function of interstellar grains at small angles.