You wouldn’t think the Yarkovsky effect would have any real significance on a half-kilometer wide pile of rubble like the asteroid 101955 Bennu. With a currently estimated mass somewhere between 60 and 80 billion kilograms, Bennu seems unlikely to receive much of a nudge from differences in heat on the object’s surface. But the people who specialize in these things say otherwise. Sunlight warms one side of the asteroid while the other experiences the cold of space. Rotation keeps the dark side radiating heat, accounting for a tiny thrust.