http://arxiv.org/abs/2105.12816
We present a chronology on the formation and early evolution of the Oort cloud, and test the sequence of events of its formation by simulating the formation process in subsequent amalgamated steps. These simulations start with the Solar system being born with planets and asteroids in a stellar cluster orbiting the Galactic center. Upon ejection from its birth environment, we continue to follow the Solar system’s evolution while it sojourns the Galaxy as an isolated planetary system. We conclude that the range in semi-major axis between $\sim 100$\,au and several $\sim 10^3$\,au still bears the signatures of the Sun being born in a $\apgt 1000$\,\Msun/pc$^3$ star cluster, and that most of the outer Oort cloud formed after the Solar system escaped. The escape, we argue, happened between $\sim 20$\,Myr and $50$\,Myr after birth of the Solar system. Today, the bulk of the material in the Oort cloud ($\sim 70$\%) originates from the region in the circumstellar disk that was located between $\sim 15$\,au and $\sim 35$\,au, near the current location of the ice-giants and the Centaur family of asteroids. This population is eradicated if the ice-giant planets were born in orbital resonance. Planet migration or chaotic orbital reorganization, occurring while the Solar system is still a cluster member is, according to our model, inconsistent with the presence of the Oort cloud. About half the inner Oort cloud, between $100$ and $10^4$\,au, and a quarter of the material in the outer Oort cloud $\apgt 10^4$\,au could be non-native to the Solar system but was captured from free-floating derbis in the cluster or from the circumstellar disk of other stars in the birth cluster. Characterizing this population will help us to reconstruct the Solar system’s history.
S. Zwart, S. Torres, M. Cai, et. al.
Fri, 28 May 21
2/56
Comments: Accepted for publication in A&A (17 pages)