Shude Mao

Using the motions of millions of stars, astronomers have built a 3D map of the dark halo. Its shape is not a sphere, but an elongated, flattened cloud. Surprisingly, the halo's long axis is almost perpendicular to the stellar disk. This orientation hints at a possible 'flip' of the disk in the past

Gravitational kicks from distant giant planets knock small rocky worlds (super-Earths) near the star out of the system. The ejected planet becomes a lonely wanderer. This same mechanism can shuffle the orbits of the remaining planets and even send them plunging into the star.