The Yarkovsky Effect
When we observe the heavens in astronomically-meager time scales, the universe seems to be in a state of perfect order. Heavenly bodies seem to have designated elliptical orbits and rarely ever tread away from them. But this is not the case in relatively longer timeframes, especially for smaller objects such as asteroids.
When scientists give accurate predictions for whether an asteroid poses a threat to Earth or not, they utilize a myriad of different tools to study every possible feature of the asteroid’s path. On short timeframes, it is possible to use basic laws to predict their future trajectory, but this data will prove to be misleading. The falsely-ordered nature of these asteroids tends to break into chaos as their orbits are dependent on multiple factors, and one of the most major factors is the Yarkovsky effect.
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Like everything in the universe, asteroids rotate about their axis. During its day, the side of the asteroid facing the Sun heats up, and eventually cools down when the side rotates away from the Sun. While cooling, the radiant heat previously received by the asteroid is emitted as radiation in the opposite direction. This emission exerts a force on the asteroid, deviating it from its original path by a small fraction. Over time, this force accumulates its effect on the asteroid, and we notice that the asteroid has significantly shifted from its original trajectory.
The Yarkovsky effect is of noticeable value only in smaller asteroids and is largely insignificant in bigger ones. It is also important to note that the direction of the asteroid’s rotation plays a key role in orbital deviation, as the Yarkovsky effect is dependent on the day/night cycle of the asteroid. Some other factors that can affect the magnitude of the Yarkovsky effect may include asteroid composition, shape, and the asteroid’s surface features.
We have already begun to understand the Yarkovsky effect at a greater depth with NASA’s OSIRIS-REx spacecraft (launched in 2016), which is currently studying the popular asteroid ‘Bennu’ with the aim of better asteroid-trajectory predictions, to safely estimate whether an asteroid poses any danger to Earth in the near or far future.
By Ayush Shivkumar (Batch 21) of IISER Thiruvananthapuram
