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

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.

Analysis of Sedna's Capture Through a Stellar Encounter

The paper under discussion addresses the origin of the Sedna family of planetesimals, particularly the object 90377 Sedna and similar bodies residing in the outer Solar System. These planetesimals exhibit distinct orbital characteristics, such as high perihelion distances and significant semi-major axes, which make them difficult to explain through existing models of Solar System formation. Traditional models, such as the Kuiper Belt excitation due to planetary migrations, fail to account for these objects thoroughly. This work proposes that the Sedna family may have been captured from another star during a close encounter, supporting a scenario of dynamic exchanges happening in the Sun’s birth cluster.

Overview of Findings

The study undertakes a meticulous investigation, utilizing simulations to recreate possible scenarios leading to the capture of these planetesimals, referred to as "Sednitos." This approach involves modeling a plethora of encounters with a star proposed to have a mass of around $1.8 \, \mathrm{M}_{\odot}$. The encounters are characterized by specific interactions at distances approximately between 210 and 320 AU and relative velocities around 4.3 km/s, with a pronounced inclination between 17 and 34 degrees relative to the solar ecliptic.

Interestingly, the paper asserts that through such encounters, the Solar System could have captured about 930 planetesimals into orbits comparable with those of known Sednitos, alongside an estimated 440 captured into the inner Oort cloud region. The modeling underscores a sufficient transfer of mass in terms of solar sibling’s planetesimal disk, thereby satisfactorily explaining the presence of Sedna and similar objects without invoking other extraordinary mechanisms.

Implications and Speculations

The implications of this hypothesis are profound for understanding the formation and evolution of the Solar System's outer regions, as well as the possibility of dynamic interactions in stellar birth clusters. If proven, the capture scenario would highlight the interconnectedness of star systems and suggest that the composition of objects within the Solar System could be more diverse and dynamically influenced than previously hypothesized.

Furthermore, the paper brings into question the existence of an outer planetary-mass perturber, as suggested by some models to explain the clustering of Sednitos' arguments of perihelion. Such presence may not align well with the encounter scenario proposed herein, necessitating reconsideration of perturber formation theories. Future observational data from missions like Gaia, coupled with chemical studies of stellar siblings, will be instrumental in validating or refuting these claims by linking planetesimal populations across stars.

Future Directions

For further development, this research prompts several lines of inquiry:

1. Detailed surveys and characterization of distant trans-Neptunian objects could provide further verification of predicted clustering and orbital characteristics.
2. Exploration of the Solar System’s initial conditions to assess how such an encounter might impact migration models or initial disk distributions could refine scenarios.
3. Advanced simulations considering more complex interactions and processes, such as mass loss from giant stars, might further clarify the fate of captured planetesimals around white dwarf remnants.

Overall, this paper provides a significant contribution to the field by suggesting a plausible alternative scenario for the existence of certain Solar System bodies, highlighting stellar and planetary dynamic interactions' role in shaping object distribution across stars.