The orbits of the inner planets of the Solar System – Mercury, Venus, Earth, and Mars – are highly chaotic, and previous models suggested that these planets should have collided.
However, that hasn’t happened over billions of years. A new study published on May 3 in the journal Physical Review X finally sheds light on why we have remained safe amidst a turbulent Solar System.
Through an in-depth study of the planetary motion models, a research team led by Jacques Laskar, an astronomer and research director at the National Center for Scientific Research and Paris Observatory, discovered that the motion of the inner planets within the Solar System is constrained by certain parameters.
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Scientists have discovered how planets in the Solar System “dodge” each other. Image: NASA
Unpredictable orbits
The planets continuously exert gravitational forces on each other, and these small pulls constantly make minor adjustments to the planets’ orbits.
The outer planets, being much larger than the planets closer to the Sun, are better able to resist smaller gravitational pulls and thus maintain relatively stable orbits. However, the orbits of the inner planets are still too complex to completely avoid collisions.
Astronomer Jacques Laskar simulated the orbits of the Solar System’s planets for the next 5 billion years and assessed them at various time points. Strangely enough, regardless of how chaotic the orbits of the planets in the Solar System were, he only found a 1% chance of collisions between the planets.
Using a similar approach, Jacques Laskar calculated that on average, it would take about 30 billion years for any two planets to collide.
Chaos with boundaries
Next, through mathematical research, Laskar and his colleagues identified for the first time the “symmetries” or “conserved quantities” in gravitational interactions. These factors created “real barriers that prevent the chaos of the planets,” said Laskar.
These quantities are nearly constant and prevent certain highly chaotic motions. The stability of the planets within the Solar System is the result of the influence of these quantities. They act as a tether, preventing the system from descending into chaos.
Besides providing a mathematically theoretical explanation for the apparent harmony in the Solar System, this new research may help scientists understand the orbits of exoplanets around other stars.