Comparison of forming mechanisms for Sedna-type objects through an observational simulator

Observatório Nacional, Rio de Janeiro, RJ, Brasil
e-mail: jean@on.br

Received: 19 June 2012
Accepted: 4 March 2013

Abstract

The aim of this work is to investigate the primordial orbital formation of objects in the inner border of the Oort Cloud, of which Sedna is supposedly a member. Among the several scenarios that discuss the formation of these orbits, two specific ones are compared for their ability to describe the dynamical formation of objects in the inner Oort Cloud: the planetary mass solar companion scenario that aims at explaining Sedna’s orbit through the perturbation of a distant solar system planet, and the stellar dense cluster scenario based on the perturbation of a primordial star cluster to which the Sun supposedly belonged. We constructed the orbital distribution of ice objects from the above scenarios and statisticaly compared both using an observational simulator that evaluates objects, sizes using a cumulative power law distribution with slope λ. We investigated the dependence on λ of the average number of observations realized by the simulator until one member of the inner Oort Cloud is observed. The results obtained by both scenarios show that both reproduce the orbits of Sedna-like objects well for specific values of the parameters. A statistical analysis considering a particular observational survey is also performed, and we find that the probability of obtaining a Sedna-type object from a population of 14 or less scattered objects as obtained in that survey is quite low (mostly below 15%) for both models, implying that the observation of the first inner Oort Cloud member occurred much earlier than would normally be expected for a first member detection of that population. We also conclude that it is necessary to observe new objects belonging to the inner Oort Cloud to precisely characterize which scenario is better for describing the origin of these objects. Possibly the best orbital element to analyze for a distinction between models is the inclination.