Stanley Schmidt’s The Sins of the Fathers is the first volume in his Kyyra duology. It was first published as an Analog serial in 1973 and came out in a mass-market paperback edition in 1976.
The starship Archaeopteryx is sent out with a three-man crew to a point 130 light-years from Earth, there to use modern astronomical equipment to intercept the wave front from the S Andromeda supernova. The ship returns with unexpected results.
Things did not go well on the ship. Dr. Donald Lewiston went mad and murdered skipper Dirk Borowski before he was subdued by ship’s mate Jonel Turabian. This is a major disappointment to Henry Clark, Lieutenant Commissioner of Grants, since the expedition falls under his purview.
Things will not go well for the Earth. Turabian informs his bosses that the core of the galaxy has exploded. A lethal wavefront of deadly radiation has spent 30,000 years creeping across the 30,000 light-years between the core and Earth. That wave front is at most twenty light-years from Earth.