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

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 $\sim 10^6$ pc${}^3$ volume occupied by CAR members with the inferred number density, $n=0.2{\mathrm{AU}}^{-3}$, of ISOs implied by Pan-STARRS' detection of 'Oumuamua, the required ejection mass is $M\sim 500$ $M_{\mathrm{Jup}}$ 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.

12 pages, 6 figures; accepted by ApJ 2021.5.29

References in corpus (19)

• galpy: A Python Library for Galactic Dynamics
• Origin of the Structure of the Kuiper Belt during a Dynamical Instability in the Orbits of Uranus and Neptune
• Interstellar Interloper 1I/2017 U1: Observations from the NOT and WIYN Telescopes
• The Age and Age Spread of the Praesepe and Hyades Clusters: a Consistent, ~800 Myr Picture from Rotating Stellar Models
• Col-OSSOS: Colors of the Interstellar Planetesimal 1I/`Oumuamua
• Constraining the giant planets' initial configuration from their evolution: implications for the timing of the planetary instability
• APO Time Resolved Color Photometry of Highly-Elongated Interstellar Object 1I/'Oumuamua
• Revised Geometric Estimates of the North Galactic Pole and the Sun's Height Above the Galactic Midplane
• Evidence that 1I/2017 U1 (`Oumuamua) was composed of molecular hydrogen ice
• On the rotation period and shape of the hyperbolic asteroid 1I/`Oumuamua (2017) U1 from its lightcurve
• New low-mass members of the Octans stellar association and an updated 30-40 Myr lithium age
• ACRONYM III: Radial Velocities for 336 Candidate Young Low-Mass Stars in the Solar Neighborhood, Including 78 Newly Confirmed Young Moving Group Members
• Accurate age determinations of several nearby open clusters containing magnetic Ap stars
• 1I/'Oumuamua as an N2 ice fragment of an exo-pluto surface. II. Generation of N2 ice fragments and the origin of 'Oumuamua
• Destruction of molecular hydrogen ice and Implications for 1I/2017 U1 (`Oumuamua)
• Assessing the Formation of Solid Hydrogen Objects in Starless Molecular Cloud Cores
• Streaming Motions and Kinematic Distances to Molecular Clouds
• Constraints on planetesimal disk mass from the cratering record and equatorial ridge on Iapetus
• Outgassing As Trigger of 1I/`Oumuamua's Nongravitational Acceleration: Could This Hypothesis Work at All?

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• Constraints on the Occurrence of 'Oumuamua-Like Objects
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• Predicting the water content of interstellar objects from galactic star formation histories
• Numerical Simulations of Tidal Deformation and Resulting Light Curves of Small Bodies: Material Constraints of 99942 Apophis and 1I/`Oumuamua
• Near-Discovery SOAR Photometry of the Third Interstellar Object: 3I/ATLAS
• Observable tests for the light-sail scenario of interstellar objects
• The New Astronomical Frontier of Interstellar Objects
• Fitting the Light Curve of 1I/`Oumuamua with a Nonprincipal Axis Rotational Model and Outgassing Torques
• On The Spin Dynamics of Elongated Minor Bodies with Applications to a Possible Solar System Analogue Composition for `Oumuamua