Evidence Suggesting that 'Oumuamua is the ~30 Myr-old product of a Molecular Cloud

TL;DR

This paper suggests that 'Oumuamua is approximately 30 million years old, likely originating from the Carina stellar group, and discusses the implications of its ejection mass and formation scenario based on its orbit and local stellar associations.

Contribution

It provides a detailed analysis linking 'Oumuamua's orbit to the Carina group and estimates its age and origin, challenging existing formation models.

Findings

'Oumuamua's orbit is consistent with membership in the Carina moving group.

Estimated ejection mass per star in Carina is around 500 Jupiter masses.

'Oumuamua's formation scenario from a protostellar disk is in tension with observed number densities.

Abstract

The appearance of interstellar objects (ISOs) in the Solar System -- and specifically the arrival of 1I/'Oumuamua -- points to a significant number density of free-floating bodies in the solar neighborhood. We review the details of 'Oumuamua's pre-encounter galactic orbit, which intersected the Solar System at very nearly its maximum vertical and radial excursion relative to the galactic plane. These kinematic features are strongly emblematic of nearby young stellar associations. We obtain an a-priori order-of-magnitude age estimate for 'Oumuamua by comparing its orbit to the orbits of 50,899 F-type stars drawn from Gaia DR2; a diffusion model then suggests a $\sim$ 35 Myr dynamical age. We compare 'Oumuamua's orbit with the trajectories of individual nearby moving groups, confirming that its motion is fully consistent with membership in the Carina (CAR) moving group with an age around 30 Myr. We conduct Monte Carlo simulations that trace the orbits of test particles ejected from the stars in the Carina association. The simulations indicate that in order to uniformly populate the $\sim10^6$ pc$^3$ volume occupied by CAR members with the inferred number density, $n=0.2\,{\rm AU}^{-3}$, of ISOs implied by Pan-STARRS' detection of 'Oumuamua, the required ejection mass is $M\sim 500$ $M_{\rm Jup}$ per known star within the CAR association. This suggests that the Pan-STARRS observation is in significant tension with scenarios that posit 'Oumuamua's formation and ejection from a protostellar disk.