Figure 1: Results of the authors’ simulation of a wide binary companion to the solar system. The colored lines illustrate the orbits of the four giant planets over time (the two lines are the pericenter and apocenter; close-together lines mean the orbit is circular, spread apart lines mean the orbit is eccentric). The dotted black line is the semi-major axis of the companion star, and the solid black line is its pericenter. The companion makes three close approaches to the sun and planets. First, it increases the eccentricity of Uranus and Neptune’s orbits; second, it changes Neptune’s orbit and ejects Uranus completely; finally, it ejects Neptune as well. From Figure 1 of the paper.

When Push Comes to Shove: How Wide Binaries Can Wreak Havoc on Planetary Systems

Title: Planetary System Disruption by Galactic Perturbations to Wide Binary Stars
Authors: Nathan A. Kaib, Sean N. Raymond, Martin Duncan
First Author’s Institution: Queen’s University, Kingston, Ontario, Canada

The Hypothesis

Many stars are found in pairs called binary systems, in which the stars are gravitationally bound and orbiting their common center of mass. These systems come in a range of sizes; the stars may be so close together that matter flows between them, or thousands of AU apart. (1 AU is the distance between the Earth and Sun.)

How do planets fare in such stellar systems? Many planets have already been discovered in binary systems, most orbiting only one of the stars, but some circumbinary planets have been found as well. In many binary systems, the combined gravity from both stars allows for stable planetary orbits only in certain regions of the system.

One might think that planets in a very wide binary system would be unaffected by their star’s far away companion. But because the two stars are only loosely gravitationally bound, the companion star will be more easily perturbed by forces outside the system – other nearby stars or even the tide of the galaxy. This could put the companion star on an eccentric orbit, occasionally sending it much closer to the primary star (and to the planetary system) similar to how long-period comets approach the sun from the Oort cloud. How likely is this to occur, and what effect would it have on planets? That is what the authors of this paper seek to explore.

Read more: When Push Comes to Shove: How Wide Binaries Can Wreak Havoc on Planetary Systems | astrobites.

Home           Top of page