The counselor spoke hoarsely, "Students, at present our planet is approximately 2.0221 million kilometers from that Big Ice Ball behind us, which is about 1.3% off from our initial projections. Every decade, the distance shortens by roughly 10,000 kilometers..."
The two planets are not revolving around each other, but are arranged one behind the other, nearly on the same orbit.
That is to say, both sides are circling around the center of mass of two neutron stars, moving in an elliptical orbit.
However, the gravitational force between planets is inversely proportional to the square of the distance. The closer the two planets get, the stronger the gravitational pull becomes, speeding up their approach towards each other.
Now, the distance shortens by roughly 10,000 kilometers every decade, but in the subsequent decade, it might shorten by 11,000 kilometers, and so on, getting faster and faster until they collide.
