NASA / GODDARD SPACE FLIGHT CENTER / SCIENCE PHOTO LIBRARY NASA / GODDARD SPACE FLIGHT CENTER / SCIENCE PHOTO LIBRARY
Animation depicting the Yarkovsky effect, the effect of solar heating on a rotating asteroid. This effect causes a change in the orbit of a body over time, due to emission of heat by the warmer face of the asteroid. As shown, the point facing the Sun receives the most heat, and warms up. However, there is a time lag between it being at its warmest, and re-emitting this heat into space. By the time its emission of heat energy is at its greatest, the rotation of the asteroid has moved the hot face away from the Sun. As thermal photons carry momentum, this emission acts as a push in the opposite direction, which in this case is against the direction of motion. The effect of this is seen at the end of the clip: over time, the orbital radius of this asteroid decreases. If the asteroid were rotating in the same direction as its orbit, the push would be the other way, and its orbit would increase in size.
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