Creation Node by Stephen Baxter

In the year 2255, of all the sentient beings in her universe, it was a woman named Salma, twenty years old, who was the first fully to see the object called Planet Nine. See with her own eyes, albeit moderated by her ship's instruments. If not to recognise what it was, not yet.

Not that the object turned out to be a planet, or the 'ninth' of anything. Briefly thought to be a black hole, it suddenly changes, expands and sends a message. There is something waiting on its service. Something not quite human.

As the ramifications of this event spread across the fracturing elements of humanity, it is clear that the small crew on the spot are at the centre of the most dramatic discovery in history. But theirs is not the only inexplicable event happening - impossibly, at exactly the same moment, a quasar appeared twenty-five thousand light years away, and now is heating up the solar system.

If the enigma of the creation node is not solved quickly, there may be no one left to investigate it . . .