Jack McDevitt - SEEKER

She looked skeptical. “Well, actually, it might have been any of a number of things.”

“Whatever. We don’t care what the object was. All we’re interested in is finding the missing world.”

“It might be possible. Tell me about the system again.”

“Okay,” I said. “Right now, it has two gas giants in normal orbits. It also has Margolia, which is running in a seriously exaggerated ellipse, and a dislodged moon.”

“Does the class-K have a name?”

“Balfour.” It was starting to sound good.

“And you’ve got a couple of ancient spacecraft out there, too, right?”

“Yes. And a dock that went adrift at the time of the event. The Seeker was apparently trying to jump into hyper when it blew.”

“Okay. As I understand it, the Seeker set out with those kids three years before the event.”

“That’s correct.”

“That means it probably won’t be much help. What about the other ship? The Whatzis?”

“The Bremerhaven. Its orbit doesn’t place it anywhere near Margolia when the intruder came through.”

“That’s interesting.”

“Maybe it was orbiting Balfour.”

“Any reason to think that? Or is it guesswork?”

“It’s guesswork.”

“What about the dock?”

“It would have been at Margolia when the object hit.”

“And they’re both currently in solar orbit?”

“Yes.”

“Get me the details. Everything you’ve got. The first thing we need to do is establish when it happened.”

“We already know.”

“All right. Good. That might make it possible. Send me the data. I’ll look everything over and get back to you.”

“Thanks, Shara.”

“My pleasure. I’m glad to help. It’ll be a break from my routine. Is there a deadline on this?”

“No,” I said. “It’s waited this long; I assume it can wait a bit longer.”

She laughed. “Get it to me tonight, and I’ll try to have something for you tomorrow.”

“You were right about the time of the event,” she said next evening, as we sat at the Longtree, sipping cocktails. “It happened March 1, 2745, on the terrestrial calendar.”

“That’s only a couple days away from what we figured.”

“We’re talking calendars rather than time itself,” she said. “It’s hard to deal with this sort of thing because of the odd things that happen with time when the objects are hundreds of light-years apart.”

“All right,” I said. “We know when it happened. Where do we go from there?”

A singer was doing “Fire and Ice.” It was cold and wet outside. But the Longtree was filled to capacity. A wedding party had taken over one wing, and another large group was celebrating something. Couldn’t tell what. There were occasional bursts of laughter around the room. In the center of the dining area, several couples were dancing.

“Chase,” she said, “we know where the gas giants were at the time of the event.”

“Okay.”

“They were undisturbed by the passage. That probably lets out your black hole. Had the intruder been massive, really massive, they would have been disrupted, too. But in this case, their orbits don’t seem to have been influenced at all.”

“That tells us what?”

“That the intruder was less than a tenth of a solar mass.”

“Okay.” I didn’t see how that could help. But she seemed to know where she was headed.

She finished her cocktail and ordered another round. “Might as well,” she said, “as long as Alex is feeling generous.” Rainbow, of course, was paying for the evening.

“Absolutely. Help yourself.”

“All right. So Margolia’s orbit gets stretched, and its moon goes south. The other terrestrial world, Balfour, is tossed out of the system altogether. That suggests an intruder mass at least a hundred times greater than Margolia.”

“Okay.”

“My best guess,” she said, “is a mass equivalent somewhere between a Jovian and an M-class dwarf star.”

“Shara,” I said, “I know you’re interested for academic reasons. But is any of this going to help us find Balfour?”

“Ah, you don’t have the patience you used to, Chase. If we split the difference between the Jovian and the class-M, we’re in brown dwarf territory.”

“Brown dwarf.”

“Yes. It’s a star that never quite got off the ground. Not enough mass. So it didn’t ignite.”

“It’s a dark object, then.”

“No. Not necessarily. They have enough energy to glow. They stay warm for a long time.”

“What generates the energy?”

“It’s left over from their formation. What I’m saying is that this thing won’t look at all like a star. It wouldn’t be a bright light in the sky. But if you got close enough, you’d be able to see it.”

“What would it look like?”

She thought about it. “It might resemble a gas giant illuminated from within. It would have clouds. Probably a muddy brown.”

“That seems an odd color.”

Shara had a tendency sometimes to go into lecture mode. She did it now. “Younger dwarfs are usually blood red. They’re just radiating the heat generated during formation. As they age, they cool off. More and more molecules form in their atmospheres, and they acquire clouds.”

“What kind of clouds?”

“Ferrous and silicon compounds, mostly. With some curious weather patterns.

Eventually they become dark red. In time, they’ll fade to reddish brown, and finally to brown.”

“Okay. And if one of these things came through a planetary system, it could raise hell?”

“You bet. Look, Chase, it’s massive. Probably one percent of standard solar mass.

That sounds small, but it’s a tight little package. If it gets anywhere near you, look out.”

“Can you tell what its path might have been through the system?”

“More or less. Mostly less.”

“Explain?”

“I tried a trillion combinations of intruder inclination, periastron distance, mass, and velocity.”

“Wait a minute,” I said. “Try it in the mother tongue. What’s periastron distance?”

“When it’s closest to the sun.”

“Okay.”

“So I tried all that to see if I could track it. Something that would produce the results we see. I’d say it entered and exited the system on a path that was mildly inclined to the plane of the planets, with periastron occurring between the orbits of Margolia and Balfour. Margolia, by the way, was the inner of the two class-K worlds.”

“That doesn’t sound like a guess.”

“It isn’t. There are limitations on what Margolia’s orbit could have been. If Balfour was also in the biozone, as you’re saying, it would have had to be more remote.

Anyway, with Balfour in the equation, it becomes possible to fit the orbits of the dock, the moon, and Margolia together.”

“That’s why we weren’t able to make the orbits intersect,” I said.

“Correct. You needed the fourth planet.” Her eyes were alight. She loved talking about astrophysics. “This thing would have been massive. If it had gotten really close to the central star, it would have taken it out. Like the one at Delta Karpis in the last century.”

“Okay.”

Our drinks arrived. She tried hers and set it down without reacting to it. “All right,” she said, “we also know the two gas giants were on the far side of the system when the dwarf crossed their orbits. So far, so good. But the two terrestrials weren’t so lucky. It passed close to them.”

“Shara,” I said, “why do we care so much about the dwarf?”

She pointed at my drink. Have some. I complied. “Because the dwarf can tell us where Balfour is.”

“Wonderful.”

“Not so fast. That brings us to the bad news. I can’t give you even a rough estimate where Balfour might be unless we can find the brown dwarf.”