Sedna and the birth of the solar system

The discovery of Sedna in a highly eccentric orbit well beyond the Kuiper belt was unexpected. With a perihelion of 76 AU, Sedna is too distant to interact with any of the major planets. But with a aphelion of only 1000 AU, Sedna is not sufficiently distant to interact with typical passing stars. No know perturber is capable of moving Sedna from where it currently is or putting it there in the first place. I will present several scenarios for the origin of Sedna's unusual orbit and show that the most likely scenario involves early encounters between Sedna and one or more anomalously close stars. Such encounters suggest formation of the sun in a dense cluster environment. While determining the true mechanism responsible for Sedna's orbit is not uniquely possible, the discovery of even a modest population of similar objects will readily lead to a rich understanding of their formation environment. This population is currently dynamically frozen in place and is likely the only fossil link back to the time of the birth of the solar system.