Hutch was thinking about the physics associated with black holes, how light freezes along the accretion disk, how time runs at a different pace close to the hole, how there’s really nothing there yet it still has enormous mass. There’d been talk in recent years that it might be possible to use antigrav technology to send a probe into a black hole. Rudy had thought it was impossible, that any conceivable technology would be overwhelmed. “How big’s the hole?” she asked.
“Probably not more than a few kilometers.”
Strange. The accretion disk was the most impressive physical object she’d ever seen, majestic, beautiful, overwhelming. Yet she couldn’t see what produced it.
“Hutch,” said Phyl, “the McAdams is in the area.”
They rendezvoused a few hours later. The ships had pulled back well away from the barrage of radiation, and the accretion disk was now only a glimmer in the night.
Hutch and Antonio took the lander over, and, glad for one another’s company, they settled into the common room. Mostly it was small talk, the long ride from Sigma 2711, how it was the end of January and where had the year gone? The latter remark, made by Antonio, had been intended as a joke. It fell flat, but Jon pointed out that Antonio was spending all his time with a beautiful woman, and the next time they tried something like this they should think things out more carefully.
They were looking at telescopic views when Phyl appeared, dark hair this time, dark penetrating eyes, wearing a lab coat, in her science director mode. The room went quiet.
She addressed herself to Hutch. “There’s something odd about the brown dwarf.”
“How do you mean?”
“It has too much deuterium.”
Hutch shrugged. Even Dr. Science looked amused. It was hardly a problem.
Phyl persisted. “It should not exist.”
“Explain, please.”
“Brown dwarfs are normally composed of hydrogen, helium, lithium, and assorted other elements. One of the other elements is deuterium.”
“Okay.”
“Deuterium is a heavy isotope of hydrogen, with one proton and one neutron. It was manufactured during the first three minutes of the Big Bang, and after that production got shut down. You don’t get any more by natural processes. Only small quantities were made initially. So there’s not much of it around. No matter where you look.”
“And this one has too much?” It still didn’t sound like a major issue.
“Yes.”
“What’s normal?”
“Only .001 percent. A wisp. A trace. A hint.”
“And how much does this one have?”
“Half—fifty percent. Well, forty-nine percent actually. But the point is there’s way too much. It’s impossible.”
“I can’t see that it’s a problem for us. Just log it, and we’ll let somebody else crunch the numbers and figure it out.”
“You don’t understand, Hutch.”
“I understand we have an anomaly.”
“No. What you have is an artificial object.”
Hutch wondered if Phyl had blown her programming. “You said it’s eight times the size of Jupiter.”
“Eight times the density.”
“That hardly matters. An object that big could not—”
“Hutch, don’t you see what’s happening here?”
“Not really. No.” She’d felt a lot of pressure since the loss of Rudy. And maybe she wasn’t thinking clearly, but she resented being taken to task by an AI.
“I think I do,” said Jon, who’d been sitting quietly, sipping hot chocolate. “Hutch, anything less than thirteen Jupiter masses is classified as a planet—” He turned to Antonio. “Do I have that right, Antonio?”
“Yes, Jon.”
“Because it never develops sufficient internal pressure to ignite its deuterium, let alone its hydrogen.”
“My God,” said Antonio. “Yet here’s an object eight times Jupiter’s mass. It displays surface abundances that can only come from deuterium burning. That’s impossible with 1/1000th of a percent deuterium. But deuterium ignition works perfectly if the object is born with eight Jupiter masses and fifty percent hydrogen and fifty percent deuterium. All it needs is a spark.”
“Wait a minute,” said Matt. “Would somebody please do this in English? For the slow kids?”
Jon and Antonio stared at one another. Both looked stunned. Jon was rubbing his forehead. “Think of a trace of air,” he said. “Mix it with gasoline and it’s stable. But a mixture of fifty percent gasoline and fifty percent air is highly combustible. A spark is all you need.”
“So where are we?” asked Hutch.
“Hutch,” said Antonio. “Nature can’t make, or ignite, fifty-fifty deuterium-hydrogen objects. So something else must have done it.”
“But why?” asked Matt. “Why would—?” He stopped cold.
“It’s a traffic sign,” said Hutch. “Without the dwarf—”
“Exactly right.” Antonio clapped his hands. “We said it coming in. Without the dwarf, the black hole would be invisible. Somebody just passing through, who doesn’t know in advance it’s there, could get gobbled up.”
“So,” said Matt, “who put it here? Who’d be capable of an engineering operation like that?”
“There’s something else that might interest you,” Phyl said later, when they were getting ready to start on the last leg of the voyage. Antonio had been reading. Hutch was absorbed with a checklist. Only Antonio looked up. “Yeah, Phyl,” he said. “What have you got?”
“I’ve been searching for hydrogen-deuterium brown dwarfs.”
“And?”
“There’s nothing in the scientific literature. Nobody’s ever seen one.”
“Okay.”
“But there’s a fictitious character, Kristi Lang, who showed up in some books written during the early twenty-first century. She’s an astrophysicist, and she locates some brown dwarfs exactly like this one. She eventually produces evidence to indicate that somebody is marking solitary black holes, exactly the way this one is marked. They each get a lighthouse. Because they’re the dangerous ones.”
“So who makes the lighthouses?”
“She has no way of knowing. She doesn’t even have a superluminal at her disposal.”
“How about that?” said Antonio. “I guess she called it.”
“Not really.” Hutch pushed away from the display that had absorbed her. “This isn’t the first black hole we’ve looked at. The Academy’s been to three. The Europeans have visited two. Nobody’s ever reported anything like this before.”
“The others,” said Phyl, “all had natural companions. You could see them from far away. This one, though, if you didn’t know in advance it was there, would be an ambush.”
Hutch told us a story tonight, how, when she was first starting her career, she’d taken a research party to Iapetus to see the statue left there thousands of years ago by the Monument-Makers. How they’d found the tracks of the creature who’d made the statue, and how they matched with the statue so they knew it was a self-portrait. She talked about following the tracks onto a ridge, where she could see the creature had stood and stared at Saturn. And she thought how alone it had been, how big and cold and uncaring the universe was. Melville’s universe. You get in the way of the whale, you’re dead. And she says she thought how intelligent creatures, facing that kind of empty enormity, are in it together. She says she felt the same way today, looking at the brown dwarf. The lighthouse.