A recent study suggests that a planet-sized object may have influenced the orbits of the four outer planets in our solar system, potentially clarifying the unusual paths they follow today.
Jupiter, Saturn, Uranus, and Neptune do not have perfectly circular orbits, and their trajectories do not lie precisely on the same plane, which has puzzled scientists for decades.
A team of researchers, led by planetary scientist Renu Malhotra at the University of Arizona, proposed a theory that a star-sized object, which passed through the solar system approximately 4 billion years ago, could have nudged these giant planets into their current orbits.
The researchers conducted 50,000 computer simulations over 20 million years, varying the size, speed, and proximity of the visiting object. Their findings indicated that in about 1% of cases, the object's passage caused the orbits of the outer planets to shift into the patterns observed today.
The simulations showed that the object, potentially 50 times the mass of Jupiter, approached very close to the outer planets, even grazing Mercury's orbit. One simulation that closely matched the present solar system featured an object about eight times the mass of Jupiter, which passed as close as 1.69 astronomical units to the sun, just beyond Mars' orbit.
This research suggests that encounters with such objects may not be rare, as brown dwarfs and similar entities are relatively common in the universe. Further exploration is needed to understand how these flybys could have affected not only the gas giants but also terrestrial planets like Earth and Mars.