The chaotic orbit of Pluto intrigues

Since its discovery, the ninth planet of the Solar system has been widely studied, and has been subject to naming controversy (Pluto has since been classified as a dwarf planet). During its overview by the probe new horizons85 years after its detection, scientists have discovered a remote world that is completely frozen, but still grappling with geological activity.

An orbit strangely different from its neighbors

But it’s probably its orbit who intrigues the most astronomers and planetary scientists: with its 248 Earth years of revolution, Pluto is located at a distance of about 40 AU from the Sun — nearly 6 billion kilometers. But its orbit being strongly eccentricthis distance varies along its path around the Sun, moving Pluto away from our Star up to nearly 50 AU at its aphelion (point of the orbit furthest from the center), and bringing it closer to our Sun up to nearly 30 AU at its perihelion — for each orbital periodPluto thus spends about twenty years orbiting closer to the Sun than Neptune !

Another astonishing characteristic: unlike the other planets of our Solar System, which generally have orbits that are very slightly inclined with respect to the ecliptic plane (plan that defines, from a point of view heliocentricthe plane of the Earth’s orbit), Pluto has an inclined orbit of 17° compared to the orbits of its neighbors.

In an attempt to understand the different processes that led Pluto’s orbit to differentiate itself from its neighbours, scientists have developed various models to simulate the past and future of Pluto’s orbit. dwarf planetputting in passing light an astonishing property protecting Pluto from a possible collision with Neptune: this condition of orbital resonance — known as the resonance of medium movement — allows the two planets to be located at nearly 90° from longitude celestial from each other when they are at the same heliocentric distance.

Moreover, the point that Pluto reaches at its perihelion is well above the orbital plane of Neptune, giving rise here to a new type of orbital resonance known as the vZLK oscillation, in reference to the three scientists who studied the phenomenon by trying to solve the “three-body problem”, aiming to determine the relative movements of three bodies with respect to each other from the laws of motion of Newton.

New studies carried out at the end of the XX^and century would indicate that Pluto’s orbit would be chaotic — minute variations in initial orbital conditions could cause exponential orbital divergences within tens of millions of years. But this chaos would seem limited: the numerical simulations of Pluto’s orbit tend to show that the two previously mentioned orbital properties of Pluto (the mid-motion resonance, and the vZLK oscillation) would persist on timescales up to billions of years, making Pluto’s orbit a stable orbit over large time scales.

Consider the whole Solar System to solve the orbit of Pluto?

But scientists still can’t figure out the origins of Pluto’s surprising orbital features (as well as those of the Plutinos, trans-Neptunian objects sharing orbital characteristics similar to those of Pluto). However, several hypotheses have emerged, such as the theory of planetary migration, now commonly accepted, according to which Pluto would have been dragged into its current mid-motion resonance by Neptune, during migration at the beginning of the history of the Solar System to its outer regions. If this theory is valid, other trans-Neptunian objects would be likely to share this same resonance condition, which has since been verified thanks to the discovery of a large number of Plutinos. But still no answers to explain the strong inclination of Pluto’s orbit!

A team of American-Japanese researchers then chose to integrate the effects of other giant planets of our solar system (Jupiter, Saturn and Uranus) in new study, in order to identify their possible impacts on the orbit of Pluto. Thanks to a digital model simulating the future orbit of the dwarf planet over five billion years and including eight different combinations of disturbances from the giant planets, the scientists were able to determine that the combined disturbances generated by the three giant planets — Jupiter , Saturn and Uranus — were needed to recreate Pluto’s vZLK wobble, the arrangement of masses and orbits of the giant planets defining a narrow range in which such an oscillation would be possible.

According to the scientists, such results would indicate that the orbital conditions of the trans-Neptunian objects would have been largely disturbed during the period of planetary migrations at the beginning of the history of the Solar System, allowing a good part of them – including Pluto — to be brought to this state of oscillation vZLK. Thus, the orbital inclination of Pluto would have originated during this migratory dynamics, but scientists are unable to establish precisely the mechanisms at the origin of such orbital particularities.

This discovery, showing the impact of the orbits of giant planets on the orbital conditions of trans-Neptunian objects, could motivate further studies on the migratory history of giant planets, and could lead in the near future to the discovery of a new mechanism. dynamics that could explain the origins of the orbital inclination of certain trans-Neptunian objects.