Once upon a time in the Oort cloud; when did the Sun Lost its Siblings

Abstract The Sun was born together with a few thousand other stars in a clustered environment. So long as it was a cluster member, no asteroid ejected by the giant planets could remain bound to the Sun, preventing the formation of an Oort cloud. The number of asteroids in the Oort cloud and their combined mass can then be used to time the moment the Sun left the nest. If the Sun left within the first 5 Myr, the Oort cloud would have been up to 4 times more massive than today’s best estimate. The Oort cloud would be considerably less massive than today’s best estimate if the Sun left later than 17 Myr. The orbital distribution of the inner Oort cloud (between ∼ 100 and ∼ 104 au) and the detached Kuiper-belt populations are even more sensitive to the moment the Sun lost its siblings. The morphology of the low-eccentricity inner-Oort cloud are most sensitive to the Sun’s escape time and can further constrain the parent-cluster parameters.