Dust-scattered ultraviolet halos around bright stars

Abstract

We have discovered ultraviolet (UV) halos extending as far as 5° around four (of six) bright UV stars using data from the Galaxy Evolution Explorer satellite. These halos are due to scattering of the starlight from nearby thin, foreground dust clouds. We have placed limits of 0.58 ± 0.12 and 0.72 ± 0.06 on the phase function asymmetry factor (g) in the FUV (1521 Å) and NUV (2320 Å) 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. © 2011. The American Astronomical Society. All rights reserved.