Colliding solar systems, artwork. The solar systems of each star contain a protoplanetary dust disc (red for one, blue for the other), which contains large bodies such as those at lower centre, as well as dust grains and every size in between. The shape of each dust disc has been distorted by the gravitational pull of the other, and streams of material are colliding at lower centre. It has been hypothesised that our solar system may have gone through such an interaction early in its history, disrupting the outer Kuiper Belt of cold icy bodies. Such an interaction may have taken place when the Sun was between 30-200 million years old. It is now 4.6 billion years old.