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Effects of planetary radius contraction on scattering

Hrannar Jónsson, Viktor LU (2020) In Lund Observatory Examensarbeten ASTK02 20201
Lund Observatory - Undergoing reorganization
Abstract
The observed high orbital eccentricities of many giant exoplanets is thought to be the result of gravitational scattering between planets. Outcomes of planet-planet scattering can result in some planets being lost by ejections into interstellar space, or collisions between planets or with the star. The likelihood of collisions for a planet with a certain mass, increases with larger radii.
After planets have been formed they will then cool and contract, which probably affects the rate of collisions and the evolution of planetary orbits.

The purpose of this thesis is to examine how planetary contraction affects the outcomes of planet-planet scattering.
By the use of numerical simulations I analyze of the outcomes of three 1 M_J planet... (More)
The observed high orbital eccentricities of many giant exoplanets is thought to be the result of gravitational scattering between planets. Outcomes of planet-planet scattering can result in some planets being lost by ejections into interstellar space, or collisions between planets or with the star. The likelihood of collisions for a planet with a certain mass, increases with larger radii.
After planets have been formed they will then cool and contract, which probably affects the rate of collisions and the evolution of planetary orbits.

The purpose of this thesis is to examine how planetary contraction affects the outcomes of planet-planet scattering.
By the use of numerical simulations I analyze of the outcomes of three 1 M_J planet systems with fixed 1 R_J, 1.5 R_J, 2 R_J radii, as well as a changing radii that follows a contraction curve from a cooling model for giant planets based on general cooling theory of Brown Dwarfs.

The results show that larger planetary radii indeed lead to more collisions, which in turn produces lower final eccentricity distributions. While the timescales for collisions remained the same as for the fixed radii, more collisions occurred earlier within that time-frame for the changing radii systems.
The use of present-day radii underestimates the rate of collisions, which planetary systems with contracting radii giants otherwise experience. The cumulative eccentricity distribution for simulations with changing radii also showed lower final eccentricities, as expected from the increased collision rate. Although the 2 R_J set showed similar amounts of collisions and ejections as the changing radii simulation, the final eccentricity distribution differed significantly. Perhaps suggesting that the time dependence of the collision rate has an effect on planetary orbital evolution. (Less)
Popular Abstract (Swedish)
Sedan den första bekräftade upptäckten av planeter utanfört vårat solsystem år 1992 har över 4000 fler hittats. Den data man har kunnat samlat ger ett gott underlag till att jämföra med resultaten av datorsimuleringar, i hopp om att bättre kunna förstå hur planetsystem formas och utvecklas.

Planeter formas i en såkallad protoplanetär skiva, bestående av 1% stoft och 99% gas, som roterar runt en ung stjärna. Gasen i skivan ger uppstånd till motstånd som förhindrar planeternas omloppsbanor från att ändras markant. Efter att gasen försvinner börjar sedan en utveckling i omloppsbanorna då planeterna gravitationellt interagera med varandra.
Nyformade planeter har en hög mängd värme som dem sedan strålar bort, vilket innebär att planeten... (More)
Sedan den första bekräftade upptäckten av planeter utanfört vårat solsystem år 1992 har över 4000 fler hittats. Den data man har kunnat samlat ger ett gott underlag till att jämföra med resultaten av datorsimuleringar, i hopp om att bättre kunna förstå hur planetsystem formas och utvecklas.

Planeter formas i en såkallad protoplanetär skiva, bestående av 1% stoft och 99% gas, som roterar runt en ung stjärna. Gasen i skivan ger uppstånd till motstånd som förhindrar planeternas omloppsbanor från att ändras markant. Efter att gasen försvinner börjar sedan en utveckling i omloppsbanorna då planeterna gravitationellt interagera med varandra.
Nyformade planeter har en hög mängd värme som dem sedan strålar bort, vilket innebär att planeten kyls ner över sin livstid. I fallet av gasplaneter innebär nerkylningen också att den tjocka atmosfären ökar i densitet, och att planeten i helhet blir mindre.

Bland dem observerade planeterna kan man märka att många jätteplaneter har betydligt mer ovala banor än gasjättarna i solsystemet. Denna höga excentricitet tror man är en produkt av gravitationella interaktioner när planeter möts på nära håll, då planeter även kan komma att kollidera med varandra eller kastas ut ur planetsystemet.
Med numeriska simulationer har forskare kunnat studera hur excentricitetsfördelningar påverkas av interaktionerna, och jämfört med observationell data.

Förutom planeternas massa så har även radien en roll i hur planeter försvinner ur systemet. Det här arbetet har som ändamål att utforska effekten som sammandragningen av gasjättar kan ha på utvecklingen av planeternas omloppsbanor. Resultaten från numeriska simulationer ska hjälpa med att besvara skillnaden på hur planeter förloras, samt den slutliga excentricitets fördelningen. (Less)
Please use this url to cite or link to this publication:
author
Hrannar Jónsson, Viktor LU
supervisor
organization
alternative title
Effekterna av sammandragande planetära radier på spridning
course
ASTK02 20201
year
type
M2 - Bachelor Degree
subject
publication/series
Lund Observatory Examensarbeten
report number
2020-EXA166
language
English
id
9024403
date added to LUP
2020-07-06 11:31:48
date last changed
2020-07-06 11:31:48
@misc{9024403,
  abstract     = {{The observed high orbital eccentricities of many giant exoplanets is thought to be the result of gravitational scattering between planets. Outcomes of planet-planet scattering can result in some planets being lost by ejections into interstellar space, or collisions between planets or with the star. The likelihood of collisions for a planet with a certain mass, increases with larger radii. 
After planets have been formed they will then cool and contract, which probably affects the rate of collisions and the evolution of planetary orbits.

The purpose of this thesis is to examine how planetary contraction affects the outcomes of planet-planet scattering.
By the use of numerical simulations I analyze of the outcomes of three 1 M_J planet systems with fixed 1 R_J, 1.5 R_J, 2 R_J radii, as well as a changing radii that follows a contraction curve from a cooling model for giant planets based on general cooling theory of Brown Dwarfs. 

The results show that larger planetary radii indeed lead to more collisions, which in turn produces lower final eccentricity distributions. While the timescales for collisions remained the same as for the fixed radii, more collisions occurred earlier within that time-frame for the changing radii systems.
The use of present-day radii underestimates the rate of collisions, which planetary systems with contracting radii giants otherwise experience. The cumulative eccentricity distribution for simulations with changing radii also showed lower final eccentricities, as expected from the increased collision rate. Although the 2 R_J set showed similar amounts of collisions and ejections as the changing radii simulation, the final eccentricity distribution differed significantly. Perhaps suggesting that the time dependence of the collision rate has an effect on planetary orbital evolution.}},
  author       = {{Hrannar Jónsson, Viktor}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Lund Observatory Examensarbeten}},
  title        = {{Effects of planetary radius contraction on scattering}},
  year         = {{2020}},
}