by Ian Douglas
“First squadron away,” Fletcher told him.
“Thank you, CAG.” The twelve fighters of the Black Demons were accelerating toward the system’s heart. Twelve more, the Impactors, were gathering, preparing for boost. The Ghost Riders were dropping now from America’s rotating flight decks.
Gray continued studying the gigantic objects before America. He had downloaded all the information Konstantin had provided on the star, including astronomer Tabetha Boyajian’s original paper, as well as reports of when the Kepler space telescope had first trained its sights on KIC 8462852. At that time, centuries ago, there had been a strange moment of dimming—as if something massive had passed in front of the star. One of the wilder possibilities discussed at that time suggested that Kepler had glimpsed a Dyson sphere under construction, a tremendously unlikely event. The chances that Kepler had recorded the fluctuating light stream from KIC 8462852 at just that brief moment in the star’s history when a Dyson shell was still being assembled were so small as to be completely negligible.
Eventually, astronomers had dismissed the possibility of alien megastructures around KIC 8462852. The dip in light was caused—must be caused—not by technologically advanced aliens, but by gravitational darkening brought on by the star’s unusually high rate of spin.
Regardless, Tabby’s Star remained a stellar curiosity, but not one demanding immediate exploration.
As Gray stared at the artifact that was Tabby’s Star, though, he began to understand some of the long-standing enigma surrounding it. And he also now knew why both the Agletsch and Konstantin had been so insistent.
Automatically, he scanned surrounding space, watching for possible threats. The TRGA was dropping away astern, a blurred, silver-gray circle. “Interesting,” Gray said, thoughtful.
“Admiral?” Gutierrez prompted.
“I find it intriguing that there just happens to be a TRGA here in the Tabby’s Star system.”
“You think maybe the locals built it? Them?”
“I don’t know, Captain. I wish I did. Too many unknowns.” He thought a moment. “Konstantin? Log this new gate as the Boyajian TRGA.”
“Noted, Admiral.”
Off to one side, an immense nebula revealed its twisted internal structures in pale light. The ship’s AI-provided data overlays identified it as NGC 7000—the North America Nebula. That vast cloud of interstellar dust and gas must be pretty close by, he thought, to appear so large in the local sky.
There was a nearby star, too, piercingly bright and with the actinic blue-white gleam of a welder’s torch, appearing more brilliant on America’s visual displays than Venus did at her brightest on Earth. The computer-generated overlay named it as Deneb—Alpha Cygni—and, again, it must be very close to Tabby’s Star indeed to appear that luminous.
But the true visual spectacle lay directly ahead, where Tabby’s Star was a hot, white glare bright enough to obscure any background stars. America had emerged from the Boyajian TGRA only eight astronomical units from the star, close enough that it showed as a small but dazzlingly bright disk. That light illuminated a spherical cloud of motes surrounding the star extending out in all directions to more than five AUs. It also lit a number of much larger objects orbiting the star closer in. The largest, when Gray increased the magnification of the image, looked like a ragged fragment of slightly curved metal, but it must have been titanic in size to be visible at this range.
He highlighted the fragment in his mind. “How big is that thing?”
Dean Mallory, the ship’s tactical officer said, “According to our instruments, that thing is over three million kilometers across!”
And it was not alone. There were hundreds of other visible fragments glinting in the light, ranging in size up to about half a million kilometers, and hundreds of thousands, perhaps millions more that appeared to be the size of large asteroids and rubble, all confined to a broad, flat ring around the star.
“Can we get the magnification any higher?” Gray demanded.
“That’s the limit of our resolution, Admiral,” the sensor officer told him.
“Very well.” They would have to wait until the fighters got in close.
What he could now see was grainy and low-res, but the ship’s AI was working to clean up the image. It wasn’t so much that the picture was blurred by distance as that his brain was having difficulty interpreting what he was seeing. That largest piece of debris, for instance: only gradually was Gray becoming aware that the thing was covered with craters, ranging in size from barely visible pockmarks to one huge blemish thousands of kilometers across. It looked . . . yes, he could make it out now. Whatever had created that largest crater had actually punched through the relatively thin shell. He could see stars visible through the hole. All of the pieces, he realized now, were covered with craters as thickly as the surface of the Moon or of Mercury. Now what could have caused—
Of course. Those fragments—and there were millions of them—had been in orbit for a long time, and it looked like they were traveling about their sun in massive clumps. The mutual gravity of those massive pieces was trying to impose order on chaos. Those fragments were traveling in the same general direction, but they must have been colliding and re-colliding with one another for centuries.
Sure . . . that was it. Tabby’s Star was such a long way from Earth that when the odd light fluctuations had first been detected at the dawn of the twenty-first century, what terrestrial astronomers had been watching was what had already happened here all the way back in the year 535 ce. That meant that the chaotic tumbling and grinding melee up ahead had been going on continuously for at least nineteen hundred years or so, and quite possibly for much longer than that.
As he watched, a piece of dull-gleaming metal the size of a small continent slowly ground into another, slightly smaller piece. Fragments drifted gently away. Metal glowed white-hot at the impact area. Smaller pieces struck other pieces . . . a cascade of slow-moving destruction.
The megastructure built around KIC 8462852 was steadily destroying itself, the larger fragments attracting the smaller, the collisions grinding the pieces to dust. How long, Gray wondered, had that been going on?
“Konstantin?” Gray called. “How far from the star is that debris field?”
“The orbital belt is fairly thick, Admiral,” the Konstantin clone replied. “But the largest fragments appear to be in a circular orbit at one point eight five astronomical units from the star.”
Gray ran some quick calculations through his in-head math coprocessor. Given the star’s mass of 1.43 times that of Sol, a planet or other body in orbit at a distance of 1.85 AUs would have a period of . . . yes . . . about 750 days. That confirmed quite nicely that the star’s light fluctuations were indeed due to that largest fragment of debris.
Konstantin must have been monitoring his calculations. “You might also be interested in the fact,” the AI clone told him, “that the habitable zone for a star of this brightness extends from roughly one point six AUs out to nearly three AUs.”
“Meaning that those big fragments are orbiting within the star’s habitable zone.”
“Precisely.”
The term habitable zone was extremely flexible and often vague, but in general meant that distance from the local star where water—under reasonable atmospheric pressures—remained liquid. Whoever or whatever had built a Dyson sphere around Tabby’s Star might have been adapted to warmer temperatures than were common on Earth, but still required liquid water.
That fact alone should have alerted those early-twenty-first-century astronomers to the fact that whatever was obscuring the light from KIC 8462852, its 750-day period meant that it was inside the star’s “Goldilocks Zone,” the realm of habitability for Earth-type life.
With that realization came another, accompanied by a sharp stab of disappointment. Obviously there had been an advanced technological civilization here, but it was long gone. It had been gone in the year 535 ce, when the light fluctuations that ha
d first piqued the curiosity of terrestrial astronomers had started off on their long journey across space to Earth. If the gradual dimming of the star recorded in old astronomical records was the result of the breakup of the Dyson sphere, it had been gone a century before that. Whatever had destroyed the high-tech infrastructure of this system had done so when the Roman Empire existed on Earth . . . and quite possibly long before that.
Which meant that there would be no easy answers, no magical weapon for defeating the Rosette entity to be found here. If Laurie’s Stargods had walked here, they were long gone.
“Konstantin?”
“Yes, Admiral.”
“Is there any indication of what happened to the beings who built all of this?”
“Nothing definite. I will remind you, however, that human reference points and reason may not have a bearing on the problem.”
“Meaning what?”
“That it is too early to assume that the builders are extinct.”
“It’s hard to imagine that a civilization advanced enough to build a Dyson sphere would just stand by and watch the thing break up.”
“I agree. It is . . . untidy. One at the very least might assume that they would recycle the materials used in the sphere’s construction.”
“Maybe they ascended,” Gray said. “Or they just packed up and left.”
“Indeed.”
“Comm,” Gray said. “Are we getting anything in the way of comm chatter?”
“Other than among our fighters, Admiral? Negative.”
“Neutrino leakage? Gravity waves?”
“Nothing, sir.”
Glumly, Gray stared at the forward display. “No radio traffic. No laser-com signals. And no fusion reactors or gravitics technology.”
“In the year 2015, concerted efforts to listen in on electromagnetic wavelengths emanating from this system turned up nothing,” Konstantin reminded him. “We’ve known since then that any advanced civilization that might reside in the KIC 8462852 system either did not use electromagnetic wavelengths for communication or . . .”
“Or they were gone.”
“Or they were gone.”
Whether the civilization here had entered its equivalent of a technological singularity and vanished, had packed up and moved to another star, or simply become extinct for whatever reason, the result was a dry hole, as far as the mission was concerned. Gray pictured himself in front of that court-martial board trying to explain himself: “Well, we hoped to talk them into giving us a super-weapon that we could use against the Rosetters, but when we got there they weren’t home, and we had to turn around and come back empty-handed. . . .”
Fuck that. Surely there was something here that would be useful, something they could learn, something they could find and reverse engineer. Konstantin had been so sure. . . .
Shkadov thrusters, for instance.
Gray had downloaded what was available in the ship’s Net during the passage to TRGA Penrose. Shkadov thrusters had been named for physicist Leonid Mikhailovich Shkadov, who’d written a paper in 1987 with the title “Possibility of Controlling Solar System Motion in the Galaxy.” Shkadov had envisioned building an enormous mirror hanging above the sun, a light sail millions of kilometers across, balanced between the sun’s gravitational pull and the pressure of its light. Such a stationary satellite, or statite, would forever hang above the same portion of the star, and by reflecting sunlight it would create an imbalance in the star’s radiation pressure, a net excess that would create thrust and move the star in the direction of the mirror.
Obviously, a megastructure of that size and scope, utilizing as it did the entire energy output of its star, would qualify its builders for Kardashev Type II status.
Gray remembered addressing the Sh’daar Council six weeks earlier, when he’d described K-I, K-II, and K-III type civilizations. Was that what Konstantin had had in mind? Appropriate some of a K-II civilization’s technology in order to confront the Rosetters?
The trouble was, if his guess about the intelligence building a galactic Dyson sphere at the core of the Milky Way was accurate, they were still going to be way outclassed by the Rosette entity’s technology.
And . . . what would the technology required for moving a star buy them? Gray had done the math. If Sol was equipped with a solar sail reflecting half of its radiation output, the total thrust produced would be on the order of 1.28 × 1028 newtons. That was a hell of a lot of energy, yes . . . but the sun was extremely massive—around 2 × 1030 kilograms. After 1 million years, the sun would have picked up a whopping extra 20 meters per second in velocity, and been nudged something like 0.03 of a light year.
The pay-off came if you kept at it, because the acceleration was cumulative. After one billion years, the change in velocity would be up to 20 kilometers per second, and the sun would have been displaced 34,000 light years, the equivalent of a third of the width of the entire galaxy.
With the appropriate technology, it was certainly possible to move stars around and even use them as weapons . . . but the people who tried it would have to be very patient.
In the centuries since Shkadov’s paper, other schemes for moving stars had been suggested. If a star could be “squeezed” using powerful magnetic induction, or prodded with intense gravitational singularities, the star might be made to create a powerful jet that would turn it into a huge rocket. Though not, strictly speaking, a Shkadov thruster, the term was sometimes applied to any technology that could push suns around.
Either way, a civilization that could move stars around might offer Earth her one slim hope of fending off the Rosette Aliens. If the America could make contact, could establish communications with a species that had evolved such godlike powers, Earth might have a chance.
And that chance, Gray thought, no matter how slender, was worth his career if it came down to that.
But before they could make contact with this system, he had to understand it.
He stared at the debris field, watching the vast, slow-tumbling fragments of mega-engineering. Was that what he was seeing? The wreckage of a device intended to move Tabby’s Star through the galaxy? Many of the discussions of Shkadov thrusters and similar technologies assumed that they would employ Dyson spheres or Dyson swarms as well. A moving star would drag its retinue of planets along with it, of course, but a sphere enclosing the star, or, better, a cloud of habitats and solar collectors orbiting it would allow for more controlled conditions—and protection if the tortured star flared or otherwise acted unpredictably.
Gray suppressed a shudder. What kind of intelligence played billiards with its sun?
And it was just possible that the wreckage he was looking at had been brought on by a K-II civilization that had overreached itself. It had tried to move its star, and something had gone horribly, horribly wrong.
“Konstantin?”
“Yes, Admiral?”
“That cloud of objects surrounding the star out to five AUs. Is that a Dyson swarm? What the hell are we looking at?”
“I am as yet uncertain, Admiral. However, the cloud appears to be very tightly ordered. It consists of some tens of millions of artifacts in stellar orbits between three and five astronomical units from the star. Each artifact, I estimate, is spherical and measures thirty to forty kilometers across, with a mass on the order of five times ten to the sixteenth power kilograms.”
“Fifty trillion tons? They’re solid?”
“Unknown, as of yet. The fifty-trillion-ton figure applies if the object has an overall density of around two grams per cubic centimeter. But the spheres may be hollow.”
“Artificial habitats, then.”
“Quite possible. However, those spheres might also be composed of solid or near-solid computronium. They are arrayed in at least five concentric shells. We could be looking at a Matrioshka brain.”
Another staggering mega-engineering concept, a toy for a super-advanced high-tech civilization. As with a Dyson swarm, you surrounded a star with satel
lites, but rather than have those satellites be habitats holding a population of trillions, you make them out of computronium, a hypothetical computational substrate arranged with the greatest possible efficiency.
You would then arrange the spheres as concentric shells. The innermost shell uses light from its sun to carry out its assigned computations, and radiates the excess energy outward. The next shell out traps that energy and uses it, radiates the excess, and so on and on until virtually all of the star’s radiation is utilized. You get all those computronium spheres talking to each other, and you have a computer network the size of a solar system, one of staggering power.
The inhabitants of Heimdall had etched computer circuitry into the bedrock of their world, creating a planet-sized computer powerful enough to hold a virtual population numbering in the trillions living within a digital world of unimaginable detail and richness. A Matrioshka brain—the term came from the nested wooden dolls from old Russia—would be trillions upon trillions of times more powerful than that.
“My God,” Gray said quietly. “What are they thinking about?”
“That, Admiral, is unknown. I should also point out that the system currently appears to be inoperable.”
Gray hadn’t been aware that he’d spoken the thought aloud. “I know, I know. But . . . I wonder . . .”
“About what, Admiral?”
“I wonder if it would be possible to tap into whatever that colossal mind was thinking, back before someone pulled the plug.”
“That seems unlikely, Admiral, even assuming that the problems of language and of computer architecture could be overcome.”
“Not if we’re dealing with a holographic brain.”
Chapter Twenty
19 December 2425
VFA-96, Black Demons
Tabby’s Star
1127 hours, TFT
Lieutenant Gregory banked his fighter low across the crumpled, crater-pocked surface of a Tabby’s Belt fragment. The sky around him was filled with tumbling rocks.
He found the panorama amusing, in a terrifying and nerve-wracking way. Popular fiction was filled with virtual dramas set in the asteroid belt of Earth’s solar system, or in the systems of other stars, and those shows never got it right. For purposes of storytelling and suspense, they usually depicted an asteroid belt as crowded with enormous boulders and looking very much like this. Gregory’s fighter training had included a month-long deployment off Ceres, in the Sol Belt, so he knew from personal experience that the planetoids there were spread out through such an enormous volume of space that, unless you happened to be very close to one, you couldn’t see any in the sky at all. The distance between one rock and the next nearest averaged something on the order of 1 million kilometers, and could be much more than that.