Astrophysicist Susanne Pfalzner of Forschungszentrum Jülich has shed new light on the edge of our solar system, suggesting that a stellar flyby may have pushed its boundaries further out. According to Pfalzner, thousands of celestial bodies move beyond Neptune’s orbit, with many exhibiting eccentric orbits inclined relative to the planets’ common orbital plane.
Researchers Pfalzner, Amith Govind, and Simon Portegies Zwart found that some force must have lifted these trans-Neptunian objects (TNOs) from their formation disk and altered their orbits. One popular hypothesis is that the planets were once in a more compact configuration, with TNOs forming between them and being scattered outward as the planets moved to their current locations.
However, the trio’s computer simulations suggest a different explanation: a close flyby of another star could have caused the peculiar orbits. This hypothetical star, about 0.8 solar masses, passed our Sun at a distance of around 16.5 billion kilometers, or four times Neptune’s distance.
The findings not only explain the motion of TNOs but also open avenues for future research on solar system formation and dynamics. Additionally, the study prompts questions about whether other stellar encounters have shaped the orbits of celestial bodies within our solar system and beyond.
In a surprising twist, the team discovered that the star’s flyby could also explain additional mysteries within our solar system. Some TNOs got flung toward the inner solar system, potentially becoming captured by the giant planets as moons.
The study provides the first possible explanation for why outer planets have two types of moons: regular moons orbiting close to planets on circular orbits and irregular moons orbiting at greater distances on inclined, elongated orbits. The research is published in Nature Astronomy.
Source: https://www.earth.com/news/rogue-star-zoomed-by-our-solar-system-disrupted-planetary-orbits-stretched-edges/