Radial distribution of distant trans-Neptunian objects points to Sun's formation in a stellar cluster
Abstract
The Scattered Disk Objects (SDOs) are a population of trans-Neptunian bodies with semimajor axes 50 35 au) are of special interest here as an important constraint on the early evolution of the outer Solar System. The semimajor axis profile of detached SDOs at 50-500 au, as characterized from the Dark Energy Survey (DES), is radially extended, but previous dynamical models of Neptune's early migration produce a relatively compact profile.
This problem is most likely related to Sun's birth environment in a stellar cluster. We perform new dynamical simulations that account for cluster effects and show that the orbital distribution of SDOs can be explained if a particularly close stellar encounter occurred early on (e.g., M dwarf with the mass similar or equal to 0.2 M-circle dot approaching the Sun at similar or equal to 200 au).
For such an encounter to happen with a reasonably high probability the Sun must have formed in a stellar cluster with eta T greater than or similar to 10(4) Myr pc(-3,) where eta is the stellar number density and T is the Sun's residence time in the cluster.