Asteroids get spun so fast by the force of sunlight they fall apart

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Science Picture Co / Alamy

Most small asteroids are just piles of rubble in space, held together by gravity and weak molecular forces. Even the slight touch of sunlight can cause them to break up. Now we know exactly how different-shaped asteroids crumble, which might help us if one ever heads straight for Earth.

Photons  carry a tiny amount of momentum, so when sunlight hits an asteroid it can send the space rock spinning, in what is known as the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect.

“The magnitude of forces acting on these asteroids is like the …