Journal Article 1 Mention
Dynamical Instabilities and the Formation of Extrasolar Planetary Systems
Frederic A. Rasio1996
Eric B. Ford
Top 1% · 99th Percentile
1,215 citations · Astronomy and Astrophysics

TLDR

When two large planets orbit the same star, their gravitational struggle can throw one into space and push the other into a tight, nearly round path. This may explain some giant planets found very close to other stars.

Summary

1 Study Aim

The authors investigate whether dynamical instability (a breakdown of predictable orbital motion) can shape extrasolar planetary systems (planetary systems beyond our solar system). They focus on systems containing two Jupiter-like planets. The study tests whether their interactions can eject one planet and leave the other on an eccentric orbit (a stretched, noncircular path). It also examines whether extreme orbits can produce planets that later settle into very short-period paths around their stars. Two giant planets may disrupt each other, leaving one behind in a tight or stretched path.

2 Study Design

The research uses computer simulations to model systems containing two Jupiter-like planets. The simulations examine how their gravitational interactions (mutual forces between orbiting bodies) evolve. They track whether a dynamical instability develops, whether one planet is ejected, and what orbit the survivor obtains. The study also considers tidal dissipation (energy loss caused by tides) when the survivor passes close to its star. The provided abstract reports no observational sample or numerical count of simulations. The researchers used computer models to follow two giant planets and their possible fates.

3 Findings

The study reports that instability often ejects one planet while leaving the other in a smaller, eccentric orbit. In extreme cases, the survivor reaches a small periastron distance (closest approach to the star). Tidal dissipation can then circularize the orbit (make it nearly round), producing an orbital period of only a few days. The authors argue that this process may explain Jupiter-mass planets in very tight circular orbits and wider eccentric orbits around nearby stars. The findings suggest that systems like ours, with one dominant Jupiter, may not be typical. A planetary struggle can remove one giant planet and turn the survivor into a close-orbiting world.

Abstract

The existence of a dominant massive planet, Jupiter, in our solar system, although perhaps essential for long-term dynamical stability and the development of life, may not be typical of planetary systems that form around other stars. In a system containing two Jupiter-like planets, the possibility exists that a dynamical instability will develop. Computer simulations suggest that in many cases this instability leads to the ejection of one planet while the other is left in a smaller, eccentric orbit. In extreme cases, the eccentric orbit has a small enough periastron distance that it may circularize at an orbital period as short as a few days through tidal dissipation. This may explain the recently detected Jupiter-mass planets in very tight circular orbits and wider eccentric orbits around nearby stars.

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