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The Effects of Encounters on Planetary Systems in Stellar Clusters

Malmberg, Daniel LU (2010)
Abstract
Extrasolar planets are found to be on orbits very different from those of the planets in the solar system.

Gas-giant planets have been found on orbits tighter than that of the planet Mercury, often with very high

eccentricities. These orbits are surprising; models of planet formation suggest that gas giants should be

found on circular orbits with similar size to those of solar-system gas giants.



In this thesis we describe how encounters between stars in young stellar clusters can increase the eccentricities

of gas-giant planets on similar orbits to those of the gas giants in the solar system. We have measured

how common encounters are, both so-called fly-bys and exchange... (More)
Extrasolar planets are found to be on orbits very different from those of the planets in the solar system.

Gas-giant planets have been found on orbits tighter than that of the planet Mercury, often with very high

eccentricities. These orbits are surprising; models of planet formation suggest that gas giants should be

found on circular orbits with similar size to those of solar-system gas giants.



In this thesis we describe how encounters between stars in young stellar clusters can increase the eccentricities

of gas-giant planets on similar orbits to those of the gas giants in the solar system. We have measured

how common encounters are, both so-called fly-bys and exchange encounters. In the latter, a single

star is exchanged into a binary system, while in a fly-by two stars pass close to each other.



If a single star is exchanged into a binary, the effect of the companion is to periodically increase the

eccentricities and inclinations of the planets. This leads to the orbits of planets crossing, triggering

planet-planet scattering. In a fly-by, the effect of the intruder star can be to immediately eject and/or

capture one or more planets. More common, however, is that the fly-by only perturbs the orbits of the

planets, which on time scales of a few to more than 100 million years triggers planet-planet scattering.



The outcome of planet-planet scattering, whether triggered by the companion star in a binary or by the

intruder star in a fly-by, is most often the ejection of one or more planets, leaving those remaining on

more eccentric orbits.



We find that encounters in stellar clusters will significantly alter the population of planetary systems

orbiting stars in the cluster. As many stars form in some type of cluster or association, encounters

between stars can thus play an important role in determining the properties of the observed extrasolar

planet population. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Adams, Fred, Department of Physics, University of Michigan
organization
publishing date
type
Thesis
publication status
published
subject
pages
114 pages
defense location
The Lundmark lecture hall (Lundmarksalen) at the Department of Astronomy and Theoretical Physics
defense date
2010-06-15 14:00
ISBN
978-91-628-8113-9
language
English
LU publication?
yes
id
154e29e7-ffb1-4585-90c8-124e2f18f7b8 (old id 1606058)
date added to LUP
2010-05-21 11:42:37
date last changed
2016-09-19 08:45:18
@phdthesis{154e29e7-ffb1-4585-90c8-124e2f18f7b8,
  abstract     = {Extrasolar planets are found to be on orbits very different from those of the planets in the solar system.<br/><br>
Gas-giant planets have been found on orbits tighter than that of the planet Mercury, often with very high<br/><br>
eccentricities. These orbits are surprising; models of planet formation suggest that gas giants should be<br/><br>
found on circular orbits with similar size to those of solar-system gas giants.<br/><br>
<br/><br>
In this thesis we describe how encounters between stars in young stellar clusters can increase the eccentricities<br/><br>
of gas-giant planets on similar orbits to those of the gas giants in the solar system. We have measured<br/><br>
how common encounters are, both so-called fly-bys and exchange encounters. In the latter, a single<br/><br>
star is exchanged into a binary system, while in a fly-by two stars pass close to each other.<br/><br>
<br/><br>
If a single star is exchanged into a binary, the effect of the companion is to periodically increase the<br/><br>
eccentricities and inclinations of the planets. This leads to the orbits of planets crossing, triggering<br/><br>
planet-planet scattering. In a fly-by, the effect of the intruder star can be to immediately eject and/or<br/><br>
capture one or more planets. More common, however, is that the fly-by only perturbs the orbits of the<br/><br>
planets, which on time scales of a few to more than 100 million years triggers planet-planet scattering.<br/><br>
<br/><br>
The outcome of planet-planet scattering, whether triggered by the companion star in a binary or by the<br/><br>
intruder star in a fly-by, is most often the ejection of one or more planets, leaving those remaining on<br/><br>
more eccentric orbits.<br/><br>
<br/><br>
We find that encounters in stellar clusters will significantly alter the population of planetary systems<br/><br>
orbiting stars in the cluster. As many stars form in some type of cluster or association, encounters<br/><br>
between stars can thus play an important role in determining the properties of the observed extrasolar<br/><br>
planet population.},
  author       = {Malmberg, Daniel},
  isbn         = {978-91-628-8113-9},
  language     = {eng},
  pages        = {114},
  school       = {Lund University},
  title        = {The Effects of Encounters on Planetary Systems in Stellar Clusters},
  year         = {2010},
}