In 2017, the first confirmed interstellar visitor, Oumuamua, zipped through our Solar System, followed by Comet 2I/Borisov in 2019. These fleeting guests sparked curiosity about interstellar objects (ISOs) and rogue planets uncharted wanderers that could traverse space and potentially interact with our Sun. New research explores the tantalizing idea that the Solar System could permanently capture one of these cosmic drifters, and what such an event might mean.
The study, published in Celestial Mechanics and Dynamical Astronomy by Edward Belbruno and James Green, delves into the dynamics of phase space an intricate mathematical framework used to describe the possible states of a system like our Solar System. Phase space reveals pathways where an interstellar object could become gravitationally bound to the Sun.
How the Solar System Could Capture a Rogue Planet
Phase space encompasses two types of capture points for ISOs: weak capture points, where an object temporarily settles into an orbit, and permanent capture points, where it becomes a stable, enduring member of the system. According to the researchers, subtle gravitational forces, including the Sun’s tidal interactions with the galaxy, could bring an interstellar object into a state of permanent weak capture.
Objects in this state would never escape the Sun’s gravitational pull but would also never settle into a fully stable orbit, instead meandering chaotically for eons. “Permanent weak capture is possible through openings in the Solar System’s phase space,” the study notes.
While smaller ISOs like Oumuamua or Borisov might slip by unnoticed after brief visits, the arrival of a massive rogue planet would be a different story. Such a planet could generate significant orbital disturbances among the Solar System’s planets, potentially destabilizing their orbits and causing chaotic changes.
These rogue planets are no rarity. Stars frequently eject planets during their formative years due to gravitational interactions, leaving them to drift through the galaxy. Some estimates suggest rogue planets may outnumber stars, a controversial claim but one supported by simulations of planetary system evolution.
Close Stellar Encounters and Their Effects
The Solar System doesn’t exist in isolation. Nearby stars occasionally pass close enough to perturb the Oort Cloud, the vast shell of icy objects surrounding the Solar System. Every million years, two stars come within a few light years of the Sun, and six such encounters are predicted in the next 50,000 years. These gravitational nudges can send comets or even ISOs toward the Sun, potentially leading to weak or permanent capture.
The forthcoming Vera Rubin Observatory is poised to revolutionize our understanding of ISOs and rogue planets. By systematically scanning the sky, it could uncover numerous interstellar visitors, shedding light on how they behave, cluster, and interact with star systems.
The discovery of a captured rogue planet or ISO would open a new chapter in planetary science. As the study concludes, “A rogue planet could perturb the orbits of the planets in ways that may be detectable.” The question remains: will the Sun someday adopt a new planetary member, reshaping the Solar System’s delicate balance?
