Identifying Interstellar Objects Trapped in the Solar System through Their Orbital Parameters

Abstract: The first interstellar object, Oumuamua, was discovered in the Solar System by Pan-STARRS in 2017, allowing for a calibration of the abundance of interstellar objects of its size and an estimation of the subset of objects trapped by the Jupiter-Sun system. Photographing or visiting these trapped objects would allow for learning about the conditions in other planetary systems, saving the need to send interstellar probes. Here, we explore the orbital properties of captured interstellar objects in the Solar System using dynamical simulations of the Jupiter-Sun system and initial conditions drawn from the distribution of relative velocities of stars in the Solar neighborhood. We compare the resulting distributions of orbital elements to those of the most similar population of known asteroids, namely Centaurs, to search for a parameter space in which interstellar objects should dominate and therefore be identifiable solely by their orbits. We find that there should be thousands ofOumuamua-size interstellar objects identifiable by Centaur-like orbits at high inclinations, assuming a number density of `Oumuamua-size interstellar objects of $\sim 10^{15} \; \mathrm{pc^{-3}}$. We note eight known objects that may be of interstellar origin. Finally, we estimate that LSST will be able to detect several hundreds of these objects.

• The paper uses dynamical simulations to show that about 3% of interstellar objects are gravitationally captured by the Jupiter-Sun system.
• It employs the REBOUND N-body integration tool with realistic stellar velocity distributions to model trajectories and distinguish these objects from typical Solar System bodies.
• The study reveals that captured ISOs exhibit high orbital inclinations, providing a key criterion for future identification with surveys like the LSST.

Identifying Interstellar Objects Trapped in the Solar System through Orbital Dynamics

The study entitled "Identifying Interstellar Objects Trapped in the Solar System through Their Orbital Parameters" by Siraj and Loeb provides a comprehensive investigation into the possibility of identifying interstellar objects (ISOs) captured within our Solar System. The paper particularly focuses on objects analogous in size to `Oumuamua, the first detected ISO, and assesses the outcomes of their interactions with the Jupiter-Sun system. The research leverages dynamical simulations to explore the potential orbits of these captured ISOs and suggests criteria for their identification based on their orbital parameters.

Methodology and Simulations

The authors employed computational simulations to model the trajectories of `Oumuamua-sized ISOs interacting gravitationally with the Jupiter-Sun system. The simulation focused on the largest planet, Jupiter, due to its significant gravitational field. The initial conditions for these simulations involved drawing from the velocity distribution typical for stars in the Solar neighborhood, allowing for a realistic representation of interstellar velocities. The study used the REBOUND N-body integration tool, simulating particles at their closest approach to Jupiter, and integrated their trajectories backward and forward in time to identify those that were initially unbound but became bound due to gravitational interactions.

Results and Orbital Parameter Analysis

The results demonstrated that approximately 3% of the simulated ISOs were captured into bound orbits. The orbital element distributions, particularly of semi-major axis, eccentricity, and inclination, were analyzed and compared to known populations of Solar System objects, specifically the Centaurs. The analysis identified a key differentiator: ISOs captured within the Solar System tend to have higher orbital inclinations. The study concluded that a significant number of ISOs, potentially thousands, should be identifiable through Centaur-like orbits with inclinations exceeding 48 degrees, making them distinct from typical Solar System objects.

Implications and Future Directions

The paper posits that the observational identification of trapped ISOs could lend insight into the conditions and materials of other planetary systems without necessitating interstellar travel. Furthermore, such objects represent a novel scientific opportunity to study material and potentially even life signatures from outside our Solar System. The authors also note the potential for technological advancements, such as the use of high-resolution spectroscopy to differentiate interstellar from Solar System-origin objects.

Additionally, the research anticipates the potential of future astronomical surveys, like the Large Synoptic Survey Telescope (LSST), in identifying these objects due to its expansive coverage and sensitivity. The LSST could detect several hundred ISOs, thus providing a rich dataset for further investigation.

Conclusion

This paper contributes significantly to the understanding of ISOs potentially trapped within our Solar System, offering a methodological framework to distinguish and study them based on orbital dynamics. While the paper cautions about the challenges in differentiation due to similar velocities potentially shared by other celestial objects, it sets the groundwork for future empirical verification and study utilizing advanced observational technologies. In the broader context of space sciences, the study opens pathways to interstellar material analysis right within our celestial neighborhood, potentially enriching our comprehension of other star systems and the universality of celestial objects' formation and evolution mechanisms.