How Sedna and family were captured in a close encounter with a solar sibling

TL;DR

This paper proposes that the Sedna family of distant Solar System objects was captured from another star's planetesimal disk during a close stellar encounter, explaining their unique orbits.

Contribution

It reconstructs the specific stellar encounter that could have captured the Sednitos, providing a new explanation for their origin and predicting the population size.

Findings

Sednitos likely captured from another star's disk during a close encounter.

Reconstructed encounter involved a 1.8 solar mass star at ~340au impact parameter.

Predicted 930 planetesimals in the Sednitos region and 440 in the inner Oort cloud.

Abstract

The discovery of 2012VP113 initiated the debate on the origin of the Sedna family of planetesimals in orbit around the Sun. Sednitos roam the outer regions of the Solar System between the Egeworth--Kuiper belt and the Oort cloud, in extraordinary wide (a>150au) orbits with a large perihelion distance of q>30au compared to the Earth's (a=1au and eccentricity e=(1-q/a) ~ 0.0167 or q=1au). This population is composed of a dozen objects, which we consider a family because they have similar perihelion distance and inclination with respect to the ecliptic i=10--30deg. They also have similar argument of perihelion omega=340+/-55deg. There is no ready explanation for their origin. Here we show that these orbital parameters are typical for a captured population from the planetesimal disk of another star.Assuming the orbital elements of Sednitos have not changed since they acquired their orbits, we reconstruct the encounter that led to their capture. We conclude that they might have been captured in a near miss with a 1.8MSun star that impacted the Sun at ~340au at an inclination with respect to the ecliptic of 17--34deg with a relative velocity at infinity of ~4.3km/s. We predict that the Sednitos-region is populated by 930 planetesimals and the inner Oort cloud acquired ~440 planetesimals through the same encounter.