Oort Cloud Formation and Evolution in Star Clusters

The Astrophysical Journal, vol. 987, pp. 29

Abstract

Abstract It is unknown whether an Oort cloud reaches its maximum mass within its star’s birth cluster or millions of years later. Complicating the Oort cloud evolution process is the fact that comets can be stripped from orbit due to perturbations from passing stars. We explore how a star’s cluster escape time (t esc) and the time its Oort cloud reaches maximum mass (t max ) affect the Oort cloud’s ability to survive via N-body simulations. In a 14 M ⊙ pc–3 cluster, we identify 50 stars of 1 M ⊙ with a range of t esc to host Oort clouds, each with 1000 comets at t max . For each host, we consider Oort clouds that reach maximum mass 0, 50, and 250 Myr after the cluster’s formation. Each Oort cloud’s evolution is simulated in the cluster from t max to t esc. Only a fraction of comets tend to remain in orbit, with this amount depending on t max and t esc. We observe that 12%, 22%, and 32% of Oort clouds with a t max of 0, 50, and 250 Myr retain >50% of their comets at t esc, respectively. We find that the fraction of comets stripped has the relationship f = m log 10 t esc − t max Myr , where m = 0.32 ± 0.04, indicating that the longer the Oort cloud remains in the cluster, the more comets are stripped, with this fraction increasing logarithmically at approximately the same rate for each t max .

Authors 4

1. Justine C. Obidowski corresponding

   University of British Columbia · University of Toronto

   Affiliation as printed

   David A. Dunlap Department of Astronomy & Astrophysics, University of Toronto, 50 St. George St, Toronto, ON M5S 3H4, Canada

   Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada

2. Jeremy J. Webb corresponding

   University of Toronto · York University

   Affiliation as printed

   David A. Dunlap Department of Astronomy & Astrophysics, University of Toronto, 50 St. George St, Toronto, ON M5S 3H4, Canada

   Department of Science, Technology and Society, Division of Natural Science, York University, Toronto, ON M3J 1P3, Canada

3. Simon Portegies Zwart corresponding Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA, Leiden, The Netherlands

4. Maxwell Xu Cai corresponding Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA, Leiden, The Netherlands