Oort Cloud and Scattered Disc formation during a late dynamical instability in the Solar System

TL;DR

This paper investigates the formation of the Oort Cloud and Scattered Disc during a late Solar System instability, addressing discrepancies between observed and simulated population ratios by considering size and brightness differences.

Contribution

It revises the population ratio estimates by accounting for size and brightness differences between LPCs and JFCs, aligning simulations more closely with observations.

Findings

Revised population ratio between OC and SD is approximately 44.

Simulation results yield a ratio of 12, consistent within uncertainties.

Accounting for size and brightness differences improves model-observation agreement.

Abstract

One of the outstanding problems of the dynamical evolution of the outer solar system concerns the observed population ratio between the Oort Cloud (OC) and the Scattered Disc (SD): observations suggest that this ratio lies between 100 and 1000 but simulations that produce these two reservoirs simultaneously consistently yield a value of the order of 10. Here we stress that the populations in the OC and SD are inferred from the observed fluxes of new Long Period Comets (LPCs) and Jupiter-family comets (JFCs), brighter than some reference total magnitude. However, the population ratio estimated in the simulations of formation of the SD and OC refers to objects bigger than a given size. There are multiple indications that LPCs are intrinsically brighter than JFCs, i.e. an LPC is smaller than a JFC with the same total absolute magnitude. When taking this into account we revise the SD/JFC population ratio from our simulations relative to Duncan and Levison (1997), and then deduce from the observations that the size-limited population ratio between the OC and the SD is 44 (-34)(+54). From simulations we obtain 12 +- 1 but the agreement cannot be rejected by the null hypothesis.