A newly published study indicates that a planet-sized object, potentially eight times the mass of Jupiter, may have significantly influenced the orbits of the outer planets in our solar system. This finding sheds light on the unusual orbital characteristics observed among these planets.
For years, the formation of the solar system's planets has been a topic of debate among astronomers. While many theories propose that planets should orbit the sun in concentric circles on a single plane, none of the eight planets, including Earth, exhibit perfectly circular orbits. Additionally, their orbits do not align neatly with one another.
Renu Malhotra, a planetary scientist at the University of Arizona and co-author of the study, noted that the orbits of the four outer giant planets—Jupiter, Saturn, Uranus, and Neptune—show minor deviations from ideal conditions. Previous research has struggled to explain these discrepancies, as interactions between the planets alone do not account for the observed orbital features.
To investigate this issue, Malhotra and her team considered the possibility that a star-sized object may have passed through the solar system around four billion years ago, altering the orbits of the giant planets. They conducted 50,000 simulations over 20 million years, varying parameters such as the mass and speed of the hypothetical object.
While most simulations did not replicate current conditions, approximately 1% of them resulted in orbital configurations similar to those observed today. The simulations revealed that a passing object, ranging from two to 50 times the mass of Jupiter, could have influenced the orbits of the outer planets significantly.
The most successful simulation involved an object with a mass eight times that of Jupiter, which approached within 1.69 astronomical units (AU) of the sun. This distance is slightly beyond Mars' orbit, which is currently at 1.5 AU.
The results suggest that a single close encounter with a substellar object could have been sufficient to reshape the trajectories of the giant planets. Given the prevalence of such substellar bodies in the universe, encounters with them may occur more frequently than previously thought.