A Planet Living on the Edge

The planet HD 131399Ab with its parent stars.

This is an excerpt from my post on Astrobites:

Title:  Direct Imaging Discovery of a Jovian Exoplanet Within a Triple Star System
Authors: Kevin Wagner, Dániel Apai, Markus Kasper, Kaitlin Kratter, Melissa McClure, Massimo Robberto, and Jean-Luc Beuzit
First Author’s Institution: University of Arizona
Status: Published in Science

There’s a tug-of-war in the HD 131399 system.  A planet, HD 131399Ab, is being pulled in two directions.  On one side is the massive star HD 131399A.  On the other is a pair of smaller stars HD 131399B and HD 131399C.  The more massive HD 131399A is winning, but the battle is the most evenly matched that has ever been observed.  The planet’s orbit is just barely stable.  Orbiting far away from its primary host, it could be sent crashing inwards or tossed out of the system altogether.