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Distant stars hazardous to planetary systems, research suggests

Gradual changes in the way two distant stars orbit one another could wreak havoc on planetary systems residing around such stars, potentially causing planets to scatter off each other and get ejected to interstellar space, according to the latest research.

The researchers used computer simulations to model the disruptive process and also discovered many known planets outside the solar system may have gone through these disruptive episodes in the past.

"The gravity from our Milky Way galaxy and other stars in the vicinity of the binary star system will cause the orbit of a distant stellar companion to slowly change shape over time. Often this behaviour drives the once-distant star into a plunging orbit, causing the companion to pass very close to the other star's planets every orbital period," says lead researcher Nathan Kaib (Physics). Such close passages can completely destabilize a planetary system, leading to planetary scatterings, ejections, and collisions.

Many stars are members of binary star systems, a star system consisting of two stars orbiting around each other, and also around a planet. The brighter star is called the primary and the second star its companion.

"We were really excited about this new planetary disruption we'd discovered, but we became even more excited when we realized there was observational evidence of this event occurring in known planetary systems," says Martin Duncan (Physics).

The research was completed in collaboration with Sean Raymond )Laboratoire d'Astrophysique de Bordeaux). It will be published in an upcoming issue of Nature.