When the Observer returned to the new planet, it had been six months since they departed from the neutron star fragment. Since they couldn’t possibly circle the fragment to provide acceleration, the return time was two months longer than the departure time. They only had the propulsion system to rely on.
In other words, there was only one and a half years remaining until the collision when the Observer reached the new planet. In truth, the escape preparation had started six months prior to that. The information brought back by the Observer only confirmed that the need for humanity to escape once more into the unknown and dangerous cosmos.
Of course, Yao Yuan didn’t make this decision on his own. He came to this solution after long discussions with plenty of experts.
The neutron star fragment was confirmed by the Observer to be a real threat. It had the properties that they would expect from an actual neutron star fragment.