A massive interstellar object, potentially eight times the mass of Jupiter, may have dramatically altered the orbits of the solar system’s outer planets billions of years ago, according to a new study published on the arXiv preprint database.
Using advanced simulations, researchers suggested that the object passed within 1.69 astronomical units (AU) of the Sun—just beyond Mars’ current orbit—about four billion years ago. This close encounter could have influenced the paths of Jupiter, Saturn, Uranus, and Neptune, reshaping their orbits to the configurations observed today.
The study ran 50,000 scenarios, each spanning 20 million years, adjusting parameters like the object’s mass, speed, and trajectory. The simulations showed that in about 1% of cases, such a flyby could recreate the solar system’s current orbital architecture.
“We estimate that there is about a 1-in-100 chance that such a flyby produces a dynamical architecture similar to that of the solar system,” the researchers wrote.
The interstellar object’s gravitational influence could explain the planets’ moderate eccentricities and inclinations, which differ from the idealized circular orbits often modeled in simulations.
- “The scenario of a close encounter with a substellar object offers a plausible explanation for the origin of the moderate eccentricities and inclinations and the secular architecture of the planets,” the study stated.
Previous models attributed the irregular orbits to gravitational interactions among the planets themselves. The new research challenges this, suggesting a one-off event—a close encounter with a massive interstellar visitor—could better account for these anomalies.
The authors emphasized the need for further exploration into the effects of such flybys on minor planetary bodies, including the asteroid belt and trans-Neptunian objects.
If confirmed, the findings could reshape our understanding of the solar system’s early history and the potential influence of interstellar objects on planetary systems.
