Yarkovsky effect
Astrometric observations between 1999 and 2013 have demonstrated that 101955 Bennu is influenced by the Yarkovsky effect, causing the semimajor axis of its orbit to drift on average by  meters/year. Analysis of the gravitational and thermal effects has given a bulk density of ρ =  kg/m3, which is only slightly denser than water. Therefore, the predicted macroporosity is %, suggesting the interior has a rubble pile structure or even hollow. The estimated mass is .