Hearthspace

by Stephen Baxter

Genres: Space Opera

Synopsis

Thousands of years ago, a massive colony ship arrived at the Hearth - the celestial birthplace of millions of planets, ranging from habitable earth-like worlds to unimaginable hellscapes of pressure and heat. Using lightsails to navigate, humanity has spread itself across dozens of these worlds. But they have also forgotten their beginnings, where they came from... and a terrible secret is about to be unveiled.

For Commander Ulla Breen, on her first tour of duty aboard a patrol sail-ship, the universe is about to change around her. Attacked by an unknown and unthought-of enemy, she and her fellow crewmembers will face slavery, punishment and death - and so will their home planets. Because someone else has seen the richness of the inner Hearth, and plans to take it for themselves. A new enemy, but one who seems disturbingly familiar. And perhaps knows more about the history of the Hearth than even Ulla and her crew.


Faced with a complete upheaval of all she thought she knew, Ulla must survive long enough to come up with a plan - one which will unite all the disparate elements of the Hearth, and perhaps discover the reason why humanity came to Hearthspace in the first place . . .

Release date: September 25, 2025

Publisher: Orion

Print pages: 400

Sample

First contact.

Of all the teeming populations of the Alliance of Earths, it happened that the first sighting of the intrusion of the remote empire soon to be known as the Hierarchy of Worlds was made by a junior naval officer called Commander Fels Sedhi, of the lightsail ship Patrol 45.

It hadn’t been the plan.

The ship’s current mission, hundreds of days long, was essentially to transport a senior officer, Commodore Siri Mott, across Alliance space from one world to another, specifically Earth 6 to Mars 5. Routine. You always kept your eyes open for the unexpected. But the mission had nothing to do with first contact.

Which happened anyhow.

And it happened that Fels Sedhi’s own personal assignment during that crucial watch had him, and him alone, outside the hull of the 45 when the first encounter was made.

For the Alliance navy, this was already a significant moment in its own right, as it happened, coming during an early test of a new deep-space propulsion technology: a dark-matter ramjet.

It was a turning point in history, Fels Sedhi would later reflect, much later. But a heck of a mess to live through.

A dark-matter ramjet …

Start with that.

The very name excited Fels.

A brand new propulsion technology to replace, or at least supplement, the huge, unwieldy lightsails that were the standard interplanetary-travel technology to date. A new technology to be tested by the crew of his ship on this jaunt, the Patrol 45.

And here was Sedhi himself at the cutting edge, at the controls of this one-person test article, a prototype demonstrator of the technology itself, along with a flock of miniature drones. He would have made barrel rolls if he’d had the nerve, and the stupidity.

But he did swivel his tiny one-person cabin to take in the view.

And, out here, far from any planet, what a view – including the sail ship Patrol 45, its own lightsail opened up to complete porosity while it hung, immobile in space, to release Fels’ craft and send it on its way.

Hearthspace:

Fels had grown up learning and dreaming of spaceflight and its arena. And now here he was, for the first time, at the controls of his own craft. And what a craft.

And Hearthspace …

He knew the geography. From his small cabin, there at the centre of his vision he saw the brilliant pinpoint at its heart, the Hearth itself, as bright at this distance, so he understood, as the legendary Sun, the distant star of mankind, as seen from the equally legendary first Earth, origin of mankind.

But the Hearth was more massive than the Sun, and much more powerful, intense. A planet might be Earthlike at a set distance from its sun, some hundred and fifty million kilometres – which the engineers and astronomers called an ‘astronomical unit’, an AU.

The Sun burned hydrogen and helium in its fusing core. The Hearth was different.

It was a concentration of dark matter, with particles of that elusive substance forced to bond by the Hearth’s ferocious gravity – and in the process, releasing prodigious amounts of energy. The scientists called the result a ‘dark-matter star’, with a million times the mass of the Sun, and a billion times its luminosity.

And, basking in that light, planet-building was similarly scaled up. A world could be Earthlike only if it were far from its dark-matter ‘sun’: thirty thousand times as far as Earth was from its Sun.

At the academy he had been told, based on scraps of history and folklore, that it was believed that the human-origin solar system, far from here, may have had eight major planets and assorted dwarfs, comets and asteroids. An orbital complex built on length scales of multiples of the astronomical unit, the distance of Earth from its Sun.

But just as the Hearth was so much vaster and brighter than the Sun, so the planetary system of the Hearth was vastly more spread out. And in a such a roomy space, there were thought to be as many as a million planets in Hearthspace, analogues of Earth and Mars, even some Jupiters and Neptunes – the very names another legacy, it was believed, of the first migrants to come here. And there were uncountable crowds of comets and asteroids …

Given such a domain, most of the planets were isolated on similar scales – tens or hundreds of astronomical units between them, whereas in the base solar system, such planets were separated by distances of mere handfuls of astronomical units. But, even so, here in the Hearth, humanity’s sail craft were able to challenge such distances. A journey of a ninety astronomical units, under a comfortable acceleration of one constant gravity, could be achieved in just twenty-seven days. And, Sedhi had long ago learned, that the ‘day’ time unit everybody used, on whichever world they inhabited, was another inheritance from the first settlers from Earth; the standard ‘day’ used even now was based on the rotation of that far distant prototype. Sedhi had always been curious about such cultural relics, as soon as he had learned about the history of his world – indeed, his worlds. So, he knew that their very names, Earth, Mars, Venus, Jupiter, were borrowed from prototypes in the original solar system, the system of Earth: a ‘Mars’ was smaller, dryer than an Earth, a ‘Venus’ was hot, its air dense and opaque …

Roomy the space might be, but still there were so many of those planets and new worlds with archaic names, that, drifting in his tiny ship, looking back, Sedhi saw that torrent of worlds, brilliantly lit by the ferocious glare of the Hearth itself.

And, he fondly imagined, from here, he might even see the core of human civilisation in this part of Hearthspace – for the first colonists here, amid a barrage of Hearthlight and a cascade of worlds, all more or less Earthlike, had discovered an anomaly. A great scar.

‘Earthlike’ covered a spectrum of planetary types. All were mostly composed of rock and metal, with perhaps a skim of atmosphere, of oceans, depending on their evolution and history: worlds could collide. Their formation, from cascades of asteroids, was chaotic and violent. And in one corner of Hearthspace a significant piece of violence had been inflicted on a crowd of worlds, of Mercurys and Earths, Mars-types and Venus-types.

Out of this cloud of planets, a much larger rocky world – a freak, a mega-Earth, which, through an accident of formation, had come to mass as much as an ice giant, as much as ten times the mass of a ‘standard’ Earth (which had come to be the standard unit).

And through further acts of planetary violence and diversion, this rogue ploughed through an amorphous cloud of younger, less massive worlds, Mars types, Earth types, Venus types, leaving a string of destruction behind it – and alignment. The result was an unusual flock of worlds, a string of them: Mercury, Venus, Earth, Mars types in a rough row.

And this unusual formation drew the eyes of the first humans to explore this part of Hearthspace. They began to name their new territories by type, and by the date of discovery or colonisation. So, Earth 3, Mars 4, Venus 5 – a labelling more based on human history than logic of location (to the bafflement of future scholars and explorers). More bafflement might come for cartographers and navigators in generations to come as the planets drifted slowly from their neat but temporary alignment. But, others protested, by then humans would be able to push the planets neatly back in line …

People like Ulla Breen called Fels thoughtful – or other, less flattering things. But, he thought, it was no crime to take an interest in the corner of history and geography you happened to live in.

But this architecture of light and worlds was not Sedhi’s priority today – rather, he reflected now, he was exploring the source of that light: the energy to be mined from dark matter, and a new application of it.

He was familiar with the basic project.

Whereas all of the Alliance’s major interplanetary ships to date, including Patrol 45, were driven by lightsails – huge wispy structures, as much as two thousand kilometres wide, that caught the light of the distant Hearth – by comparison Sedhi’s tiny, nameless, pod-like craft was a test article. And it did not run on Hearthlight for its propulsion. Instead it was driven by scooping up dark matter itself out of apparently empty space.

That invisible, intangible substance which permeated the universe, amounting to about a quarter of its total mass-energy, and which in particular burned thickly in the Hearth itself, that vast, dark-matter star that was the linchpin of this realm, this Hearthspace, and its swarm of planets.

But now the Alliance engineers had found a way to exploit dark-matter energy itself – rather than trap its light or heat, on a smaller scale than their enormous sails, and more flexibly, more nimbly, more efficiently. Dark matter was itself essentially a field of mass-energy, waiting to be mined by humans – for example to be used by a spacecraft that could be designed to scoop up that mass-energy – and use it for propulsion.

A dark-matter ramjet …

That was the theory. Fels’s job today was to pilot this cut-down vessel, a small spacecraft shorn of the Hearthlight sails that had once propelled it, to be replaced by the energy of dark matter itself …

If it worked.

Within an hour of his undocking from Patrol 45, the mother ship, his scheduled engine-start milestone arrived. Ancillary rockets cut in, forcing the first flow of dark matter into a reactor core.

And soon he could feel that virgin engine cut in, a thrust as smooth as a mother’s caress. Powered by an energy field that had been rife when the universe itself was born. Now that cosmic energy, tamed, worked as well as the engineers had promised.

And this pilot found it handled better than any lightsail ship: far more compact and manoeuvrable, for a start. He rolled, dived down, back up again …

He indulged himself in a whoop. He could hear that his fellow officer, Ulla Breen, who was monitoring the tests back on the 45, matched it.

As the test flight went on, he easily navigated his way from one target landmark buoy to another. Given it was an assignment of such significance, this was easy, Fels told himself, as the novel little ship flew around the 45, and he murmured similar observations into his log. Drilling, chewing his way through the invisible stuff of reality.

His chronometers prodded him that that future big stuff had to wait, must get the little but important stuff out of the way first. Now came the second part of the test: miniaturisation.

For now he shut down the new dark matter drive, and allowed his own lightsail to capture the Hearth’s glow, to carry him forward. And, with a few swipes of his controls, he initiated the drone drop: he released a handful of miniature craft, drones, beacons, each similarly equipped with miniaturised dark-matter ramscoops – all based on experimental design models, all sending back reports on Sedhi’s progress to bases on the main Alliance worlds. They spread around him like a sparse cloud.

Easy stuff. No drama.

Not at first …

That was, until things started to go wrong. Until alarms sounded softly.

And history pivoted.

Distracted by the novelty of his cutting-edge test technology, Fels was actually slow to react.

The first symptom was a loss of performance.

And as his systems began to protest at the unknown, he glared around, paged through screens on the wall of his tiny one-person cabin, forced himself to process what his instruments were telling him. He tried to think.

A shadow.

The monitors were telling him that he was falling into a shadow, and so losing lightsail performance.

A shadow cast by what?

The new shadow could not come from the 45, his mother ship, because that was ahead of him: he could see it. And besides the crew had warned him about no such manoeuvre near the main ship.

No, the unexpected shadow was cast by some object behind him – and, he saw, given the geometry, the newcomer was also starting to block the light falling on the 45.

As if it were deliberately aligned that way.

With a squirt of thrusters, he swivelled in space.

And saw it.

Another ship.

Not one of ours, he murmured for the log.

And, even in that first moment, he wondered if future historians would study recordings of those words in decades to come.

Not one of ours.

Here it began.

A ship.

Not one of ours.

And so huge …

Its hull dark. Larger than the 45, he saw – and a radically different design.

A main body that was a cylinder – unlike the 45, which had, behind its sail, a clam-shell body shape. No, this ship had a different design, dominated by a blunt cylindrical body perhaps fifty metres in length and width, and topped by a wider torus at one end – giving the whole the look of a vast bolt, he saw in that first impression.

And it had a truly immense sail, wide but wispy – the sail of the 45, he knew, spanned two thousand kilometres, and this must be ten times that width. A cobweb the size of a planet …

Sedhi had never seen such a ship. Such a sail. Close to, or in the training manuals.

Belatedly, he thought to activate his personal log, to be uploaded on the fly to the 45. And he made verbal, hasty, detailed notes, even as his ship’s systems locked on to the anomaly.

A bolt-ship, he called it in his report.

And he described that sail, its enormously long cables sprawling, its edges out of sight, a sail that obstructed half of the universe … Presumably self-assembling, self-repairing …

He reported all this to the 45.

A reply came quickly.

We see it too. Just log it all, Fels.

That was Commander Ulla Breen, his control for this mission. Gather as much data as you can. Analyse, and you might miss something. All I have to do now is get the captain’s attention … A “bolt-ship”. I got that label … ’

‘Copy that … I’ll try to get more data.’

He murmured commands, and his own smart systems began to analyse the images that scrolled across his instruments. Images he could see with his naked eye. Like nothing he had seen before. A sail larger than some ice giant planets, surely …

From his point of view now the stranger’s sail was a dark plane spreading across space, tilting grandly, catching the Hearthlight, cutting the universe in two. And he immediately saw that a conventional Alliance lightsail ship, such as the 45, would be immobilised if it was plunged into that shadow. In fact, he wondered if the huge, slow manoeuvre was intended to do that, to cut off the light.

His ship, however, with its entirely independent dark-matter ramjet technology, could ignore that shadow. His secret-technology dark-matter-chewing ship. Maybe it was just as well it was secret, in the face of this …

Even so, there was probably not much more he could do out here.

He remembered his duty, standing orders. His circumstances had changed; the situation might even be hazardous. He ought to get his precious ship back home. Still containing its pilot, ideally. But even if not, at least carrying the data on the performance of his dark energy drive, the drones, and what he could see of the newcomer.

Belatedly, he began to make sure that every bit of data that he had captured, or would capture, on his own test flight and on this new incident would be downloaded to the 45.

And he ought to prep his beacons too.

Standard issue for missions like this, a beacon was a compact drone you could hold in your hand, but when pushed out of a craft was capable of self-propelling with its own miniature solar sail, and capable of observing, and sending signals, laser and radio, across hundreds of astronomical units – or further, in relays.

And, as it happened, some of his beacons today were powered by his dark energy drive, a cut-down version – another experiment – while sail-driven beacons would be immobilised like the 45 itself. So, he thought, if the worst came to the worst, by chance he had a means to send data to the Alliance, even if the 45 failed.

It gave him little comfort.

Still the intruder approached.

Fels made no attempt to manoeuvre, to escape, before he made sure all the data he had on this incident was downloaded to the beacons. Then he launched all he had. He configured some of them to head back to his origin world, Earth-class, and the rest to tail the 45, whatever became of it.

Alarm lights flashed.

A proximity report, next.

Then, a damage report. Problems with his own dark-matter sail—

It was being fired on.

He finished launching off the drones before doing anything else. With that done, it took him a couple of heartbeats to figure out what had happened.

He had already lost the sail. Just like that.

He checked his instruments. There was a feeble status signal from the lost sail, crammed with diagnostic information, all of it useless now.

A mechanical ouch.

There was some imagery. Some kind of intruder, a robot perhaps, had rushed through his rigging and neatly, efficiently, removed that miraculous dark-matter sail.

Nobody had expected such a brutal amputation.

Now more alarms, subsidiaries. A flood of information.

All this in moments.

Slowly, too slowly, in Fels’s head, his training cut in … Stern, memorised orders about a response to a hypothetical enemy aggressor.

Orders that had seemed wildly over-specified during his training. Nobody had seriously expected an assault, piracy of this apparent kind. Alliance space was not rife with bandits, pirates.

But now that was no longer true.

Who are they?

But, whoever, whatever, in the circumstances he had an instinct that it would not be a good thing for the new dark-matter drive to fall into the hands of these … raiders.

He made a decision. Pressed a self-destruct button.

Destruct for the scoop technology, while sparing his own life.

He couldn’t see it directly, but monitors showed it went like a moth in a flame. (Some moth, some flame …) Data flows withered and died. The sail, top-secret technology, burned itself up, lost its secrets in seconds.

Which gave him another idea. Hastily, he reconfigured the drones to put them into stealth mode – an option rarely used. They would take some finding by the authorities, but they could be interrogated by them, and could hopefully trail the intruder and whatever craft had taken it – and as long as the beacons weren’t detected, then whatever became of the 45 could be monitored, reported …

And now he ran down.

Fels had done all he could think of. Incidentally leaving himself stranded, in a spacecraft become a hulk, drifting with no motive power … It had all happened so quickly that he felt his energy, concentration drain away.

But he wasn’t done yet, it seemed. Even as he framed that thought, he was losing the starlight. As that vast shadow now crept between him and the 45, he lost all chance of contact. And the huge bolt-ship was closing on him.

But he didn’t feel like waiting to be just taken.

At least he could get out of this drifting coffin. He could abandon ship. Put up a fight, look for a chance to get away. His suit was pretty capable, meant for survival – though not designed for this contingency –

Just get out, man. Do it! Before they get here—

His gloved fist slammed into a red button. Half his hull blew. Amid a whirl of lost cabin air, he was fired into the immensity of space, as if he had been born, the whole universe expanding around him – the Hearth a vast cloud glowing from within.

Before him, the wall, the landscape that was the intruders’ sail.

Below, his ship, falling away.

He calculated that if he could orient himself, squirt his boot thrusters – a minor delta-V – if at least he headed towards the 45 there might be a chance he’d be picked up.

And even if he was missed, he could use the in-case-of-emergency cryo-preservation technology in the suit, as in all modern suits. Fall into a frozen sleep. Even if he was lost, left drifting, he could survive for years. Sooner that than to be taken by the unknown bandit. Or, worse, quickly killed.

Freeze.

Do it. Don’t hesitate.

He fumbled with his suit controls, a panel on his belly. Hit the cryo facility. A sharp pain in the small of his back. A needle.

‘That was quick. And way more painful than the simulations suggested,’ he muttered. ‘Thanks, medicos.’

But the numbness closed in rapidly. He was already losing motor control. Fading awareness. Pushing him under … Cold, inert gases flooding his suit …

And that invader ship, a vast shadow, was still heading towards him. Or rather, he was drifting into its path; surely it couldn’t change its trajectory quickly.

He was getting cold already.

The cryo was doing its job. Only a few more seconds, minutes, of consciousness. The suit’s emergency power packs weren’t meant for extended stays beyond vehicles.

Cold.

Suit lights off, beacons off, cryo deep-preservation option. With any luck you might evade the invader. And at least there’ll be a chance of being picked up some time in the future. By somebody. A slim chance is better than none.

Get out of there …

Evasion protocol …

With the last of his will-power, the last of his consciousness, he watched the giant invader closing on a dwarfed, helpless, overwhelmed Alliance Patrol craft.

… Your turn now, Ulla …

… At least I proved the dark-matter ram works …

… Hey. Suppose the suit does preserve me. Suppose the cryo works. Suppose somebody does find me, drifting without beacons … If I live through this …

… Slim chance …

… I made first contact. I’ll be famous. Ideally not dead and famous …

… And if I manage not to die, maybe my report will be the saving of the 45 …

… How about that, Ulla … ?

… The best I can do …

… And, you raiders, who broke my ship.

I’ll be back.

What must be recognised is that this devastating interplanetary conflict was essentially shaped, determined, by the cosmic geography of the Hearthspace, and the human geography that followed.

From a young age, our citizens understand that the bright light in the sky is not an ordinary star like those other, distant lanterns in our skies – like the Sun whose light has nurtured all mankind, save our star-travelling ancestors and ourselves. The Hearth is a dark matter star, fuelled not by the fusion of hydrogen but by the burning of dark matter: that elusive, intangible, invisible material that constitutes most of the mass-energy of our galaxy – indeed our universe.

And, fuelled by a different physics, the Hearth, our local dark matter star, has a different constitution. It is much more massive – perhaps a million times as much as our Sun. And its luminosity – its brilliance, the heat and light it gives – is as much as a billion suns.

This has consequences for the planets of that ‘sun’. And there are many of those planets, we believe perhaps millions, large and small – just as the Hearth has a million times the mass of the Sun which has a mere handful of worlds, including fecund Earth, mighty Jupiter. All is to scale.

And in our skies are planets of the kind our ancestors explored in our home solar system, and other stars: Earths, Jupiters, etc.

Lots of them.

But their distributions are quite different from the Sun’s.

There are Earths in the Hearth’s ‘habitable zone’, where the Hearthlight’s intensity is just right to nurture a living, Earthlike world. Just as the Sun has a habitable zone. But the solar system has a mere three habitable or near-habitable worlds, in Venus, Earth and Mars, with the radii of their orbits of the order of Earth’s own life-giving distance from the Sun: a distance we call an ‘astronomical unit’, one AU. At its closest to Earth, Mars comes to within a half of an AU; Venus’s orbit is about seven-tenths of an AU.

Hearthspace has many such planets. But, numerous as they are, so huge is Hearthspace, so brilliant the Hearth itself, that the spacings of such worlds are much wider than the distances that define the solar system.

Around the Hearth, a typical Earth-type and a typical Mars-type may follow orbits with radii as much as thirty thousand astronomical units – and so such distances have to be spanned regularly by an interplanetary culture, from an Earth to a Mars.

Jupiter, by comparison, the first of the outer solar system’s giants of rock, ice and water, is five astronomical units from the Sun – and an equivalent orbit in Hearthspace would map onto some hundred and fifty thousand astronomical units.

These monstrous distances can be spanned, however, by capturing the energy of the Hearth itself.

Once humans sailed on the light of the Sun, for sunlight itself has a pressure – tiny, but sufficient to push substantial craft, given wide enough sail.

Now, in Hearthspace, humans – Alliance or Hierarchy, slave or free – travel in sail ships, with monstrous sails that catch the light of the Hearth. Such craft massing a thousand tonnes, with a lightsail a thousand kilometres across, could pull its cargo at an acceleration of a standard Earth gravity – obviously a comfortable regime for human passengers.

And such craft, never refuelling, can make epic journeys – especially when relativistic effects are taken into account. At one gravity, thirty thousand astronomical units could be spanned in five hundred days – as measured aboard, but more in the outer universe, given relativistic effects at such speeds.

And in a Hierarchy craft, crossing a typical hundred and fifty thousand astronomical units could be spanned, as measured aboard, in a mere three years, four in the external universe.

And thus the first Hearthspace War unfolded, humans, free and enslaved, with craft under monstrous sails, taking years-long voyages across enormous gulfs of space …

Aboard the sail ship, Alliance of Earths Patrol 45, Commander Ulla Breen happened to be on her watch when the first formal encounter was made between the human populations of the inner worlds of Hearthspace, and those of the outer.

It was quite a moment, when she had a breath to think about it later. The first reunion since a presumed common origin – a single landing of humans on a Hearthspace world – and later diver. . .