The host star of the hot Jupiter WASP-20b has been found to be a binary star. A new paper by Daniel Evans et al finds WASP-20 to be a binary separated by 0.26 arcsecs, sufficiently close that the second star had not previously been noticed. Evans et al used the SPHERE instrument on ESO’s Very Large Telescope to find the slightly dimmer companion:
The two stars, WASP-20 A and WASP-20 B seem to be gravitationally bound, and the planet appears to orbit the brighter star. The companion star is 61 astronomical units from the planet-hosting star, close enough that it might have had a gravitational effect on the orbit of the planet.
This is relevant since hot Jupiters are thought to have been created much further from their star than their current close-in orbits, and gravitational perturbations from a third body is one suggested mechanism for causing them to migrate inwards.