The Population of Interstellar Objects Detectable with the LSST and Accessible for In Situ Rendezvous with Various Mission Designs

Abstract

The recently discovered population of interstellar objects presents us with the opportunity to characterize material from extrasolar planetary and stellar systems up close. The forthcoming Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will provide an unprecedented increase in sensitivity to these objects compared to the capabilities of currently operational observational facilities. We generate a synthetic population of ‘Oumuamua-like objects drawn from their galactic kinematics and identify the distribution of impact parameters, eccentricities, hyperbolic velocities, and sky locations of objects detectable with the LSST, assuming no cometary activity. This population is characterized by a clustering of trajectories in the direction of the solar apex and antiapex, centered at orbital inclinations of ∼90°. We identify the ecliptic or solar apex as the optimal sky location to search for future interstellar objects as a function of survey limiting magnitude. Moreover, we identify the trajectories of detectable objects that will be reachable for in situ rendezvous with a dedicated mission with the capabilities of the forthcoming Comet Interceptor or proposed Bridge concept. By scaling our fractional population statistics with the inferred spatial number density, we estimate that the LSST will detect of order ∼15 interstellar objects over the course of its ∼10 yr observational campaign. Furthermore, we find that there should be ∼1–3 and ∼0.0007–0.001 reachable targets for missions with propulsion capabilities comparable to Bridge and Comet Interceptor, respectively. These numbers are lower limits and will be readily updateable when the number density and size–frequency distribution of interstellar objects are better constrained.

The Volatile Carbon-to-oxygen Ratio as a Tracer for the Formation Locations of Interstellar Comets

“…Previously, Kim et al (2020) estimated that Borisov only lost ∼0.4 m of surface material in the solar system and similarly concluded that compositional observations were not representative of the primordial material. Hoover et al (2022) presented the orbital Figure 10. Schematic diagram showing two distinct stages of an interstellar comet's lifetime.…”

“…distribution of interstellar objects detected by LSST, assuming that all of the objects had an absolute magnitude similar to that of 'Oumuamua. We show the cumulative distribution functions for b and v ∞ in Figure 12, from Figures 12 and 15 of Hoover et al (2022). The LSST will detect objects out to b ∼ 3 au with 20 km s −1 < v ∞ < 60 km s −1 .…”

“…If the measured C/O ratio is 0.2, then the object definitively formed interior to the CO snow line. Hoover et al (2022). These are calculated using a detailed population synthesis assuming that the interstellar objects were as bright as 'Oumuamua.…”

“…The LSST will detect interstellar comets at or close to its limiting magnitude (Hoover et al 2022). For these cases, some or all of the techniques outlined in the previous subsection cannot be applied.…”

“…Future detections and compositional measurements will demonstrate whether or not these objects are representative of the population. The LSST should detect one interstellar object every year (Hoover et al 2022), and a space-based in situ rendezvous may be performed in the upcoming decade (Seligman & Laughlin 2018;Hein et al 2017;Meech et al 2019;Castillo-Rogez et al 2019;Hibberd et al 2020;Donitz et al 2021;Meech et al 2021;Hibberd et al 2022;Moore et al 2021a). The ESA's Comet Interceptor (Jones & ESA Comet Interceptor Team 2019;Pau Sánchez et al 2022) mission or the NASA concept study BRIDGE (Moore et al 2021b) may provide these observations.…”