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.

Based on the occurrence rates implied by the discoveries of 1I/‘Oumuamua and 2I/Borisov, the forthcoming Rubin Observatory Legacy Survey of Space and Time (LSST) should detect ≥one interstellar object every year. We advocate for future measurements of the production rates of H2O, CO2, and CO in these objects to estimate their carbon-to-oxygen ratios, which trace formation locations within their original protoplanetary disks. We review similar measurements for solar system comets, which indicate formation interior to the CO snow line. By quantifying the relative processing in the interstellar medium and solar system, we estimate that production rates will not be representative of primordial compositions for the majority of interstellar comets. Preferential desorption of CO and CO2 relative to H2O in the interstellar medium implies that measured C/O ratios represent lower limits on the primordial ratios. Specifically, production rate ratios of Q(CO)/Q(H2O) < 0.2 and Q(CO)/Q(H2O) > 1 likely indicate formation interior and exterior to the CO snow line, respectively. The high C/O ratio of 2I/Borisov implies that it formed exterior to the CO snow line. We provide an overview of the currently operational facilities capable of obtaining these measurements that will constrain the fraction of ejected comets that formed exterior to the CO snow line. This fraction will provide key insights into the efficiency of and mechanisms for cometary ejection in exoplanetary systems.

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Interstellar small bodies are unique probes into the histories of exoplanetary systems. One hypothesized class of interlopers are “Jurads,” exocomets released into the Milky Way during the post-main-sequence as the thermally pulsing asymptotic giant branch (AGB) host stars lose mass. In this study, we assess the prospects for the Legacy Survey of Space and Time (LSST) to detect a Jurad and examine whether such an interloper would be observationally distinguishable from exocomets ejected during the (pre-)main-sequence. Using analytic and numerical methods, we estimate the fraction of exo–Oort Cloud objects that are released from 1–8 M ⊙ stars during post-main-sequence evolution. We quantify the extent to which small bodies are altered by the increased luminosity and stellar outflows during the AGB, finding that some Jurads may lack hypervolatiles and that stellar winds could deposit dust that covers the entire exocomet surface. Next, we construct models of the interstellar small body reservoir for various size–frequency distributions and examine the LSST’s ability to detect members of those hypothesized populations. Combining these analyses, we highlight the joint constraints that the LSST will place on power-law size–frequency distribution slopes, characteristic sizes, and the total mass sequestered in the minor planets of exo–Oort Clouds. Even with the LSST’s increased search volume compared to contemporary surveys, we find that detecting a Jurad is unlikely but not infeasible given the current understanding of (exo)planet formation.