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And a Bottle of Sun

Those of you who are old enough to recall the original publicity campaign surrounding Extropa Energy's pet project - or who have dug it out of the archives in the years since - might remember the first renders of the Esilmúr Sphere: a diaphanous veil cast over hot white Esilmúr, rippling endlessly in the solar wind, and permitting the star's light to illuminate from behind a vaster-beyond-imagining rendition of their corporate logo.

Exactly none of this is true: solar sailcloth isn't translucent even when you aren't trying to wring every erg out of every photon; the ripples caused by the solar wind are too slow and on too large a scale to perceive, not to mention damped; the star is heavily managed for maximal efficiency; there is no perspective, from stargate to service, from which one might view such a logo (it's just too big); and to return to the first point, it's dark out there, in anything except deep gallé.

And yet, notwithstanding all that, it's one of the most impressive sights you'll ever see, rendered in negative as you approach it and are confronted by the stars going out across half the sky, occluded by the largest structure ever made by sophonts and their few billion robots each.

So what is Esilmúr? It's a gigastructure made from megastructures. It's the biggest, least populated world in the Empire, and indeed, in the known galaxy. And it's one of the unquestioned wonders of the universe as we know it.


The Bubble

Any conversation about Esilmúr must start with the bubble itself. As we said above, it's far from the diaphanous veil of the publicity films: solar sailcloth is light and thin, assuredly, but it is also astonishingly tough, and woven through with strands and MEMS which allow its position to be sensed, rigidity to be controlled, and movement directed to keep and alter its shape, not to mention the components of the nanorepair system to patch micrometeoroid holes. Even many solar sailors coat their sails with solar foil as an additional source of energy without adding a significantly to its thickness.

While the Esilmúr bubble is similar to this in theory, in practice it needs to withstand the stresses and pressures of the bubble entire, without the ability to spill wind from a sail, and is designed to pass every photon emitted from the Esilmúr sun through multiple layers of systems designed to extract every possible usable erg and leave behind only the lowest-grade waste heat that gives the bubble its dull gallé glow. Thus, if we may analogize normal solar sailcloth as a fine silk organza, by the same standard, the bubble's fabric is a heavy, quilted canvas.

And yet, when considered on its grand scale - having an internal surface area 240 million times that of Eliéra, and yet significantly less than its mass - it is light, thin, and as ephemeral-seeming as the most delicate soap bubble floating in the faintest breeze, well-suited to be supported by the faint pressure of stellar photons and the solar wind.

Not that anyone has ever perceived it as such, save through telescopes from afar. It's simply too big for the unaided eye to see, or mind to apprehend. Even from within, standing (with the help of magnetic boots, for a Cirys bubble has no gravity within) on the surface, there is only the endless dark wall and bright sky extending to the limits of vision in all directions, without the least suggestion of a visible curve - even when one of the vast, slow, damped ripples is passing underfoot - and yet somehow returning to the far sky behind the sun overhead.

(Certain visitors who do not normally suffer from agoraphobia have been known to develop the Esilmúr-specific variant when confronted with this endless wall under the eternal noon. Those finding themselves anxious about falling into the sun or becoming lost on the infinite self-similar plane are advised to make contact with the Averic Mental Health Center, the leading facility for the treatment of megagoraphobia here in one of the few places where it is relevant.)


Vertigo at the Vertices

Of course, a Cirys bubble is of very little use without some means of ingress and egress, which at Esilmúr is provided by the twelve portal facilities. If you imagine a convex regular icosahedron large enough to touch the bubble from the inside with its vertices, the portals are located where each vertex would be. Apart from Acme and Nadir, located at the solar poles, the ten Vertex Portals are each named after prominent former directors of the company.

Imagine, for a moment, that you are approaching the Esilmúr bubble from one of the three stargates in the system (from Mazir, Mírlan, and Palaxias, respectively). The shadow of the Sphere grows as you watch, from an inky blot against the stars to a vast dark wall blotting out half the universe. At least the slight glow of heat gives you reason to believe that there's something there; if it wasn't for that, you could be falling forever into an empty void.

And then, just as you're having to work hard to convince yourself that you're not, you spot it. A tiny pinpoint of light against the darkness. As you rush towards it, it slowly becomes clear to you: a bright and cheery upwelling of light against the black, perhaps a dozen miles across, and around it the friendly blinking of navigation lights and signals. You've found the entrance.

It's not only the entrance, though. The main structure of the Vertex Portals, stapled through the bubble like a grommet in a sail, serves as much as a vent and an engine as it does a doorway. Suspended in the center of each miles-wide opening is a vast array of magnetic coils which serve to regulate, block, or accelerate as required the outflow of the solar wind through each of the portals - and, of course, the portals are the only place in the Sphere where it is permitted efflux. In this way, along with controlled stiffening, relaxation, and magnetic shaping of the solar sailcloth, any rippling or other distortion of the shape of the bubble is damped down, and it is kept stable in its position around the star.

But this does greatly limit the amount of the portal usable by starships, since traditional designs are partial neither to intense magnetic fields nor sailing against particle geysers. Rather, visitors must traverse the remaining passage between the portal wall and the geyser, which is normally done with engines shut down and under thrust provided by the portal's own tractor-pressor systems - not least because this volume is shared by the endless ongoing traffic of antimatter freighters. Docks and locks are located within.

There are very few reasons for the visitor to pause here, though. Each Vertex Portal is ringed by its share of Esilmúr's antimatter factories. From each of the five notional facets which meet there, a fractal tree of superconducting cables, bus-bars, and power beams runs to terminate in the massive arrays of contraterragenerators, particle cascades, charge separators, plasma accreter-chillers and encapsulation arrays responsible for the Sphere's primary product.


Dangling Above Infinity

While Esilmúr has a population measured only in the tens of millions - composed almost entirely of contractees and their families working for Extropa and its partners - almost none of it lives near the Vertex Portals, or any of the other facilities described below.

(Ultra-high-energy processes are efficient and miraculous creators of wonders, but they also make uncomfortable neighbors.)

To house all of Esilmúr's population, therefore, there are the danglehabs. In most respects they resemble conventional cylinder habitats (of the vivarium type that introduces light at one end and distributes it internally, rather than using linear windows), save that the sunward end of the cylinder is capped with a window-dome opening on the endless noon.

The outward end, however, is the anchor from which the entire habitat hangs. Rather than orbiting, the danglehabs are built on the statite pattern, maintained in position by the pressure of the solar wind on its sails; of course, in their case, rather than individual sails, the danglehabs hang from the fabric of the bubble itself, balanced between it and the central star's gravity, from which they also tap power.

Well, they don't hang directly from the bubble. It is on occasion necessary or convenient to move a danglehab to a new position, and so the branching end of the cable from each hab's anchor is attached to a duodectet of giant mechanical spider-bots, who in turn cling to anchors on the inside of the bubble, and can walk slowly across its surface when repositioning is called for.


The City of Brass

Moving now from the edge to the center of the bubble, buried within the outer atmosphere of the star itself - and visible only to those watching through helioscopes as a series of bright arcs crossing the stellar surface - is the stellar husbandry framework, nicknamed by locals "the City of Brass".

The City is no different from any of the other stellar husbandry arrays wrapping the stars of the Empire's core worlds, or indeed from the prototypical Athanor Array. It is merely the hardest-working stellar husbandry array of them all, much as Esilmúr is its hardest working star.

For while all the arrays engage in moderation of stellar activity and prolongation of its lifespan, the City of Brass was also built to prioritize utilization of the star as a matter processor. While stirring up the interior of the star is part of the latter for all arrays, the City was built specifically to mine the heavy elements formed in the star's heart, and manipulate its internal reactions to create and harvest exotic post-transuranics, lifting this harvested mass in plumes from the corona and out to working platforms within the Sphere's volume. In time, these same manipulators will be used to feed hydrogen masses back into the star, replenishing its fuel stores to burn on forever.


Lenses and Lasers and Mirrors, Oh My

Just above and just below the star, at its acme and nadir poles, a careful observer might be able to pick out a couple of small dark spots. You might think that this indicates something special, given the brightness of everything else inside this vast sphere designed to keep photons within, and you would be right. Those spots indicate where the City of Brass generates gravity lenses, focusing the star's light into a pair of powerful pseudo-lasers.

Why? Well, as we mentioned, there are working platforms for various high-energy applications orbiting freely within the Sphere, and this is how power is supplied to them. The gravity lenses on either side of the star generate these absurdly powerful beams of energy. Mirror complexes (initially polar statites, balanced between the star's gravity and the thrust of the power beam, but later in the distribution process free-orbiting mirrors) split up the beams and distribute them to all the hungry working platforms in their various orbits, a shining web of light throughout the Sphere.

You can't see this light-web, of course. There's no atmosphere within the bubble, and hence no atmospheric scattering. A freely available AR layer, on the other hand, makes every laser - from the main axis that seems to bisect the star like a giant pearl on a necklace to the smallest individual power feed - blaze brightly against the sky. After all, it seems a little unfair that one can be incinerated instantly by something that leaves no trace of its passing.

That said, should anyone be insane enough to mount an attack on Esilmúr, it is beyond unlikely that anyone has designed ray shielding that can carry that load. (Assuming, for the sake of argument, that they have somehow breezed past the galaxy's largest supply of missile-grade antimatter on the way in.)


Smelters of the Impossible

Speaking of those working platforms, the most prominent of those are the six smelter-platforms arranged in a rosette around the central star. These belong to Atalant Materials, ICC, who partner with Extropa to receive their energy - both in the form of direct beaming and antimatter - straight from the source.

No finished products are made here: these vast agglomerations of industry, equipped with state-of-the-art plasma accreters, nucleon smelters, probability kilns, matter-handlers, and even more exotic instruments produce exotic materials in industrial quantities: orichalcium, gluonic string, chrysadamantium, muon metals, metastabilized neutronium, thermal superconductors, synthetic dark matter, floatstone, magnetomatter and chromomatter, and more.

Many are products or partial products of The Ring, the high-energy particle accelerator whose many segments fill out the orbit of the rosette, and many shipments of them all depart the Sphere from the Crucible, the largest of the smelter platforms, which is built around one of the few permanent wormholes used in the Empire, connecting the Crucible directly to the forges of Qechra.


Second Only To The Big One

And the antimatter?

They don't keep that inside the Sphere, for safety reasons. (Speaking of things which are uncomfortable neighbors... especially to ultra-high-energy processes.)

So, back when you were on your way in from the stargate, did you look behind you, at the outer system?

That rosette of giant planets with their tender moons?

Don't land on them.

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