Stephen Baxter: Exultant

He had long passed the closest approach achieved by his older self, Pirius Blue, on his scouting jaunt. Nobody in human history had ever approached the event horizon of a supermassive black hole so closely — and he had to go in a lot closer yet.

Nothing he saw was real, of course. All he saw was a Virtual rendering, reconstructed in wavelengths he was comfortable with, the glare turned down; if he had looked out of his blister he would have been blinded in an instant. But he thought he could sense the churning of this dish of plasma the size of a solar system, perhaps even the gut-wrenching gravities of the event horizon itself. He could feel the vast astrophysical processes around him. He was a mote trapped inside an immense machine.

“One minute to closest approach to the horizon,” Bilson warned.

Pirius felt his heart beat faster, but he tried to keep his voice light. “Remember your training. We practiced on rocks a couple of hundred kilometers across. Today we’re hitting a target a hundred million klicks wide. It ought to be easy.”

“But,” Cabel said dryly, “it’s a hundred million klicks of black-hole event horizon.”

“Shut up,” said Bilson, the fear sharp in his voice.

“No flak,” Cabel said. “They still haven’t seen us. We might actually live through this.”

“Thirty seconds,” the navigator called.

“Stand ready.”

And suddenly it was ahead of him, the center of everything, a sphere of glowing gas like a malevolent sun rising from the curdled accretion disc. The event horizon itself was invisible, of course: dark on dark, it was a surface from which not even light could escape. The glow he saw was the final desperate emission of infalling matter.

Under the control of its CTC processor, the ship rose up from the plane of the disc.

Pirius looked down as the accretion disc fell away. At the disc’s inner edge the infalling matter, having been spun and churned and compressed in its final frantic orbits, at last reached the event horizon. Wisps and tendrils, gaudy and pathetic, snaked in from that inner edge, glowing ever more feverishly.

He looked ahead into the ball of churning gas that surrounded the event horizon. The horizon was a sphere, but vast, a sphere as wide as Mercury’s orbit. The greenship’s path should take it skimming up toward its pole, kissing the surface tangentially at the point of closest approach, a precise one hundred kilometers from the mathematically defined surface of the event horizon itself.

A shining, electric-blue path appeared in the complicated Virtual sky before Pirius. Projected by navigator Bilson it was his computed course, designed to take him to the hundred-kilometer closest approach distance. Though they would pass vanishingly close to the event horizon of a supermassive black hole, there was nothing to fear from tides: Chandra was, paradoxically, too big for that, and in fact they could fall all the way down through the event horizon without feeling a thing.

Seconds left. The last million kilometers fell away, the immense curved surface started to flatten beneath the prow, and the mist of tortured matter cleared ahead of him -

To reveal a shining netting.

“Pull up!” Bilson screamed.

Pirius dragged at his controls, but the ship’s proximity sensors had reacted before he did. The ship climbed up and away. The electric-blue path disintegrated and vanished.

Suddenly the texture of that wall was fleeing beneath his prow. He made out an irregular mesh of shining threads, spread out like the lights of an immense city, all of it obscured by a storm of infalling plasma. This close he could see no signs of curvature; the event horizon was effectively a plain above which the greenship fled.

Bilson started to bring up magnified images. That structure really was a kind of net, a mesh of silvery threads. Small black shapes crawled along those threads — but they were “small” only on this tremendous scale; the shortest of those threads must have been a thousand kilometers long. The dominant structure was hexagonal, but the hexagons were not regular, and the effect was more like a spiderweb than a net.

Bilson breathed, “A web big enough to wrap up the whole of the event horizon. I think those black things are ships.”

Cabel asked, “Xeelee?”

“I guess. Not a design we’ve seen before. They seem to be trapping the infalling matter. Feeding off it. And look, there are more ships coming up from inside the mesh.”

“Then this is the central Xeelee machinery,” Bilson said. “What they use to make their nightfighters, to run their computing. This netting is the engine of the Prime Radiant. It must have taken a billion years to build.”

Lethe, Pirius thought. What have we got ourselves into?

Cabel called, “I hate to hurry you. But those flak batteries are waking up.”

Pirius called, “Bilson—”

“Understood, Pilot.”

A new path was laid in, a shining blue road that ducked down into the netting. The ship started to track the new course — but it bucked and swept up again.

“It’s that mesh,” Bilson shouted. “We weren’t expecting structure over the event horizon. The netting is actually under our hundred-kilometer ceiling, but the ship’s fail-safes won’t let us get close enough.”

Pirius thrust his hands into the controls. “I’ll override.” Even as he pushed the ship’s nose down, the systems fought back, and the ride was bumpy. “But I can’t hold this for long. Cabel, get the range finder working.”

Two cherry-red beams lanced out beneath the fleeing ship. Their paths were deflected in arcs, extraordinarily elegant, by Chandra’s ferocious gravity. Pirius, glancing down, saw the triangulating starbreakers slice through the netting as they passed, like burning scalpels passing through flesh. The intersection point should have been at about the level of the event horizon, but he couldn’t make it out.

“We’re doing a lot of damage,” Cabel reported. “Those flak batteries are definitely growing interested.”

“Never mind the flak,” Pirius growled. “There’s nothing we can do about the flak. Prepare the weapon. Bilson, are we at the right altitude?”

“I can’t tell,” Bilson said. “It’s not working — not the way it’s supposed to. There’s some kind of distortion when the beams pass through that netting.”

Cabel said, “We’re running out of time—”

Lethe, Pirius thought. To have come all this way and to fail, here… He held the ship steady on its course. “Do your best.”

“Yes, sir.”

Cherry-red light flooded Pirius’s cockpit.

“They found us!” Cabel yelled.

He was right; the ship was about to be triangulated by two, three, four starbreakers. Pirius snapped, “I need an answer, Navigator!”

“Now!” Bilson screamed.

“Engineer! Fire!”

Cabel didn’t acknowledge, but Pirius felt the shudder, familiar from training, as the cannon was fired, and twin point black holes shot out of the heavy muzzles mounted on the greenship’s main hull.

Once the shells were away Pirius relaxed his grip on the manual controls. The ship lifted itself up and away, twisting to evade attack, its CTC processor enabling it to respond faster than any human reaction. The cherry-red starbreaker glow dissipated.

Pirius lay back and sucked in a deep breath. Still alive.

The greenship shuddered, as if it were a toy boat bobbing on a bathtub.

“That was the detonation,” Cabel said.

Bilson was silent for a few seconds, gathering data. Then he said, “No damage. The weapon worked, but we must have missed the horizon.”

Pirius felt a heavy despair descend. “All right,” he said. “Keep gathering data. Maybe we can figure this out yet.”