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The effects of fly-bys on planetary systems

Malmberg, Daniel LU ; Davies, Melvyn B LU and Heggie, Douglas C. (2011) In Monthly Notices of the Royal Astronomical Society 411(2). p.859-877
Abstract
Most of the observed extrasolar planets are found on tight and often eccentric orbits. The high eccentricities are not easily explained by planet-formation models, which predict that planets should be on rather circular orbits. Here we explore whether fly-bys involving planetary systems with properties similar to those of the gas giants in the Solar system can produce planets with properties similar to the observed planets. Using numerical simulations, we show that fly-bys can cause the immediate ejection of planets, and sometimes also lead to the capture of one or more planets by the intruder. More common, however, is that fly-bys only perturb the orbits of planets, sometimes leaving the system in an unstable state. Over time-scales of a... (More)
Most of the observed extrasolar planets are found on tight and often eccentric orbits. The high eccentricities are not easily explained by planet-formation models, which predict that planets should be on rather circular orbits. Here we explore whether fly-bys involving planetary systems with properties similar to those of the gas giants in the Solar system can produce planets with properties similar to the observed planets. Using numerical simulations, we show that fly-bys can cause the immediate ejection of planets, and sometimes also lead to the capture of one or more planets by the intruder. More common, however, is that fly-bys only perturb the orbits of planets, sometimes leaving the system in an unstable state. Over time-scales of a few million to several hundred million years after the fly-by, this perturbation can trigger planet-planet scatterings, leading to the ejection of one or more planets. For example, in the case of the four gas giants of the Solar system, the fraction of systems from which at least one planet is ejected more than doubles in 108 yr after the fly-by. The remaining planets are often left on more eccentric orbits, similar to the eccentricities of the observed extrasolar planets. We combine our results of how fly-bys affect Solar-system-like planetary systems, with the rate at which encounters in young stellar clusters occur. For example, we measure the effects of fly-bys on the four gas giants in the Solar system. We find, that for such systems, between 5 and 15 per cent suffer ejections of planets in 108 yr after fly-bys in typical open clusters. Thus, encounters in young stellar clusters can significantly alter the properties of any planets orbiting stars in clusters. As a large fraction of stars which populate the solar neighbourhood form in stellar clusters, encounters can significantly affect the properties of the observed extrasolar planets. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
celestial mechanics, planet-star interactions, stars: kinematics and, dynamics, planetary systems, open clusters and associations: general
in
Monthly Notices of the Royal Astronomical Society
volume
411
issue
2
pages
859 - 877
publisher
Wiley-Blackwell
external identifiers
  • wos:000286988800010
  • scopus:79551587734
ISSN
1365-2966
DOI
10.1111/j.1365-2966.2010.17730.x
language
English
LU publication?
yes
id
62316ca5-eac9-4463-8046-e86f4d2a80b4 (old id 1869014)
date added to LUP
2011-04-19 11:07:39
date last changed
2017-08-27 03:22:29
@article{62316ca5-eac9-4463-8046-e86f4d2a80b4,
  abstract     = {Most of the observed extrasolar planets are found on tight and often eccentric orbits. The high eccentricities are not easily explained by planet-formation models, which predict that planets should be on rather circular orbits. Here we explore whether fly-bys involving planetary systems with properties similar to those of the gas giants in the Solar system can produce planets with properties similar to the observed planets. Using numerical simulations, we show that fly-bys can cause the immediate ejection of planets, and sometimes also lead to the capture of one or more planets by the intruder. More common, however, is that fly-bys only perturb the orbits of planets, sometimes leaving the system in an unstable state. Over time-scales of a few million to several hundred million years after the fly-by, this perturbation can trigger planet-planet scatterings, leading to the ejection of one or more planets. For example, in the case of the four gas giants of the Solar system, the fraction of systems from which at least one planet is ejected more than doubles in 108 yr after the fly-by. The remaining planets are often left on more eccentric orbits, similar to the eccentricities of the observed extrasolar planets. We combine our results of how fly-bys affect Solar-system-like planetary systems, with the rate at which encounters in young stellar clusters occur. For example, we measure the effects of fly-bys on the four gas giants in the Solar system. We find, that for such systems, between 5 and 15 per cent suffer ejections of planets in 108 yr after fly-bys in typical open clusters. Thus, encounters in young stellar clusters can significantly alter the properties of any planets orbiting stars in clusters. As a large fraction of stars which populate the solar neighbourhood form in stellar clusters, encounters can significantly affect the properties of the observed extrasolar planets.},
  author       = {Malmberg, Daniel and Davies, Melvyn B and Heggie, Douglas C.},
  issn         = {1365-2966},
  keyword      = {celestial mechanics,planet-star interactions,stars: kinematics and,dynamics,planetary systems,open clusters and associations: general},
  language     = {eng},
  number       = {2},
  pages        = {859--877},
  publisher    = {Wiley-Blackwell},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {The effects of fly-bys on planetary systems},
  url          = {http://dx.doi.org/10.1111/j.1365-2966.2010.17730.x},
  volume       = {411},
  year         = {2011},
}