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 of 'Oumuamua-size interstellar objects identifiable by Centaur-like orbits at high inclinations, assuming a number density of 'Oumuamua-size interstellar objects of ∼ 10 15 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.

Capture of interstellar objects: a source of long-period comets

“…This may indicate that some of them are captives, but it may also, as for short-period comets, reflect an origin in a prograde disc of planetesimals. Note that these results contrast with those of Siraj & Loeb (2019), whose captives are of shorter P, lower e and higher i. Cut-ting our results at their 75th percentile for semi-major axis (a < 16 au) shows that these Centaur-like objects form only 0.2% of the overall captive population, though we do not see the same proclivity for high i in this regime as they do. Figure 2 shows the hyperbolic excess speeds v ∞ of all objects that were consequently captured, which are much lower than the 26 km s −1 of 'Oumuamua or 32 km s −1 of Borisov.…”

“…Namouni & Morais (2018) suggest that Jupiter's retrograde, co-orbital asteroid has an interstellar origin and was captured 4.5 Gyr ago. Integrating trajectories undergoing a close encounter with Jupiter, Siraj & Loeb (2019) found that objects captured in this way may have orbits similar to those of the 'Centaurs' with inclination i > 48 • and concluded that those may be captured ISOs. Grishin et al (2019) demonstrated that interstellar objects may be captured as a result of interactions with a primordial protoplanetary gas disc.…”

Detecting Interstellar Objects through Stellar Occultations

“…In addition to 'Oumuamua, CNEOS 2014-01-08 (Siraj & Loeb 2019a) was tentatively the first interstellar meteor discovered larger than dust, and 2I/Borisov (Guzik et al 2019) was the first confirmed interstellar comet.…”

Galactic tide and local stellar perturbations on the Oort cloud: creation of interstellar comets

“…The existence of an interstellar comet cloud could partly explain the slightly hyperbolic comets and potential interstellar objects that might have been detected in the solar system but not yet classified as such (see e.g. Ashton et al 2018;Siraj & Loeb 2019). A future detailed study of the evolution of the TICs created by the tides and stellar encounters is needed to draw more solid conclusions.…”