An Observational Upper Limit on the Interstellar Number Density of Asteroids and Comets

Abstract

We derived 90% confidence limits (CL) on the interstellar number density (${\rho }_{IS}^{CL}$) of interstellar objects (ISO; comets and asteroids) as a function of the slope of their size-frequency distribution and limiting absolute magnitude. To account for gravitational focusing, we first generated a quasi-realistic ISO population to ~750 au from the Sun and propagated it forward in time to generate a steady state population of ISOs with heliocentric distance <50 au. We then simulated the detection of the synthetic ISOs using pointing data for each image and average detection efficiencies for each of three contemporary solar system surveys --- PS1, the Mt. Lemmon Survey, and the Catalina Sky Survey. These simulations allowed us to determine the surveys' combined ISO detection efficiency under several different but realistic modes of identifying ISOs in the survey data. Some of the synthetic detected ISOs had eccentricities as small as 1.01 --- in the range of the largest eccentricities of several known comets. Our best CL of ${\rho }_{IS}^{CL}=1.4\times 10^{-4}$ au${}^{-3}$ implies that the expectation that extra-solar systems form like our solar system, eject planetesimals in the same way, and then distribute them throughout the galaxy, is too simplistic, or that the SFD or behavior of ISOs as they pass through our solar system is far from expectations.

accepted for publication in AJ

References in corpus (5)

• Steady-State Size Distributions for Collisional Populations: Analytical Solution with Size-Dependent Strength
• The Main-Belt Comets: The Pan-STARRS1 Perspective
• Realistic Detectability of Close Interstellar Comets
• Flipping minor bodies: what comet 96P/Machholz 1 can tell us about the orbital evolution of extreme trans-Neptunian objects and the production of near-Earth objects on retrograde orbits
• Detection of an intergalactic meteor particle with the 6-m telescope

Cited by in corpus (38)

• Initial characterization of interstellar comet 2I/Borisov
• Initial Characterization of Interstellar Comet 2I/2019 Q4 (Borisov)
• Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U1 'Oumuamua
• The Natural History of 'Oumuamua
• 2I/Borisov: A C${}_2$ depleted interstellar comet
• 1I/2017 U1 (`Oumuamua) is Hot: Imaging, Spectroscopy and Search of Meteor Activity
• Col-OSSOS: Colors of the Interstellar Planetesimal 1I/`Oumuamua
• Detection of CN gas in Interstellar Object 2I/Borisov
• APO Time Resolved Color Photometry of Highly-Elongated Interstellar Object 1I/'Oumuamua
• Tuning the Legacy Survey of Space and Time (LSST) Observing Strategy for Solar System Science
• Implications for planetary system formation from interstellar object 1I/2017 U1 (`Oumuamua)
• 1I/`Oumuamua as a Tidal Disruption Fragment From a Binary Star System
• Tidal fragmentation as the origin of 1I/2017 U1 ('Oumuamua)
• The Orbit and Size-Frequency Distribution of Long Period Comets Observed by Pan-STARRS1
• `Oumuamua as a messenger from the Local Association
• Prospects for Backtracing 1I/`Oumuamua and Future Interstellar Objects
• Oort cloud Ecology II: The chronology of the formation of the Oort cloud
• A hypothesis for the rapid formation of planets
• Capture of interstellar objects: a source of long-period comets
• Pole, Pericenter, and Nodes of the Interstellar Minor Body A/2017 U1
• Very Large Telescope Observations of Interstellar Comet 3I/ATLAS. II. From Quiescence to Glow: Dramatic Rise of Ni i Emission and Incipient CN Outgassing at Large Heliocentric Distances*
• Searching for water ice in the coma of interstellar object 2I/Borisov
• The digest2 NEO Classification Code
• The Galactic Interstellar Object Population: A Framework for Prediction and Inference
• Dust bombardment can explain the extremely elongated shape of 1I/'Oumuamua and the lack of interstellar objects
• Tails: Chasing Comets with the Zwicky Transient Facility and Deep Learning
• High-Drag Interstellar Objects And Galactic Dynamical Streams
• Capture of interstellar objects II: by the Solar system
• Retrograde orbits excess among observable interstellar objects
• Detecting Gravitational Scattering of Interstellar Objects Using Pulsar Timing
• Near-Discovery SOAR Photometry of the Third Interstellar Object: 3I/ATLAS
• Fitting the Light Curve of 1I/`Oumuamua with a Nonprincipal Axis Rotational Model and Outgassing Torques
• Error dependencies in the space-based CNEOS fireball database
• Detecting Interstellar Objects Through Stellar Occultations
• Shape-Driven Selection Effects for Aspherical Near-Earth Objects in Systematic Surveys
• Machine Learning Methods for Automated Interstellar Object Classification with LSST
• A Catalogue of Interstellar Material Delivery From Nearby Debris Disks
• Implications for the formation of Oort cloud-like structures and interstellar comets in dense environments