Detection of radiation pressure acting on 2009 BD
  We report the direct detection of radiation pressure on the asteroid 2009 BD, one of the smallest multi-opposition near-Earth objects currently known, with H ~ 28.4. Under the purely gravitational model of NEODyS the object is currently considered a possible future impactor, with impact solutions starting in 2071. The detection of a radiation-related acceleration allows us to estimate an Area to Mass Ratio (AMR) for the object, that can be converted (under some assumptions) into a range of possible values for its average density. Our result AMR = (2.97 \pm 0.33) x 10^(-4) m^2 kg^(-1) is compatible with the object being of natural origin, and it is narrow enough to exclude a man-made nature. The possible origin of this object, its future observability, and the importance of radiation pressure in the impact monitoring process, are also discussed. 
Marco Micheli, David J. Tholen, Garrett T. Elliott
astro-ph.EP