If the twin Sun theory is correct how close?
Turns out than twin suns are the most common type of system
https://www.space.com/37186-sun-long-lost-twin-nemesis.html
Oct 21, 2016 - Brown and Batygin originally suspected that Planet Nine existed because of its effect on the orbits of objects in the Kuiper Belt, extending that idea shows how the unseen world could be affecting the inner Solar System as well. "It continues to amaze us; every time we look carefully we continue to find that …https://www.forbes.com/sites/bridaineparnell/2016/…/planet-nine-tilting-solar-system/