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Alexander Mustill. Profile picture.

Alexander Mustill

Researcher

Alexander Mustill. Profile picture.

Fly-by encounters between two planetary systems I: Solar system analogues

Author

  • Daohai Li
  • Alexander J. Mustill
  • Melvyn B. Davies

Summary, in English

Stars formed in clusters can encounter other stars at close distances. In typical open clusters in the Solar neighbourhood containing hundreds or thousands of member stars, 10-20 per cent of Solar-mass member stars are expected to encounter another star at distances closer than 100 au. These close encounters strongly perturb the planetary systems, directly causing ejection of planets or their capture by the intruding star, as well as exciting the orbits. Using extensive N-body simulations, we study such fly-by encounters between two Solar system analogues, each with four giant planets from Jupiter to Neptune. We quantify the rates of loss and capture immediately after the encounter, e.g. the Neptune analogue is lost in one in four encounters within 100 au, and captured by the flying-by star in 1 in 12 encounters. We then perform long-term (up to 1 Gyr) simulations investigating the ensuing post-encounter evolution. We show that large numbers of planets are removed from systems due to planet-planet interactions and that captured planets further enhance the system instability. While encounters can initially leave a planetary system containing more planets by inserting additional ones, the long-term instability causes a net reduction in planet number. A captured planet ends up on a retrograde orbit in half of the runs in which it survives for 1Gyr; also, a planet bound to its original host star but flipped during the encounter may survive. Thus, encounters between planetary systems are a channel to create counter-rotating planets, This would happen in around 1 per cent of systems, and such planets are potentially detectable through astrometry or direct imaging.

Department/s

  • Lund Observatory
  • eSSENCE: The e-Science Collaboration

Publishing year

2019-09-01

Language

English

Pages

1366-1376

Publication/Series

Monthly Notices of the Royal Astronomical Society

Volume

488

Issue

1

Document type

Journal article

Publisher

Oxford University Press

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • celestial mechanics
  • planet-star interactions
  • planetary systems
  • open clusters and associations: general
  • Astrophysics - Earth and Planetary Astrophysics

Status

Published

Project

  • Wallenberg Academy Fellow Project
  • IMPACT: Comets, asteroids and the habitability of planets

ISBN/ISSN/Other

  • ISSN: 1365-2966