Stellar Megastructure
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Basic Information

A Stellar Megastructure is a term I just made up to subdivide the really really huge Megastructures from the merely huge ones. Such planetary-scale and interstellar-scale megastructures have several things in common. Having now written pages about three of them, I feel like I sound like a broken record. There's nearly a dozen more to write up, so I decided this page was warranted to include the repetitive details. Why duplicate this material on page after page when I can just direct the reader here?

Any Megastructure is sure to be an impressive sight, and the existence of a megastructure on or near a planet is an obvious sign that intelligent life exists (or once did exist) on that planet. However, in some cases a megastructure may be so big as to not be obviously associated with the planet whose inhabitants designed and built it. Such a structure may be as large as a planet itself, or possibly even larger. So large that it would have taken the resources from several planets to build it, possibly even entire solar systems being converted into one or more large structures. Having such a megastructure in your telescope may indicate where the builders are now, but it doesn't necessarily tell you where they came from.

A stellar megastructure would take the resources of several worlds to build, so it's probably built by Sufficiently Advanced Technology and/or Sufficiently Advanced Aliens. The existence of such a completed project is a good warning sign that these are not folks to be taken lightly. They have superscience, rate at least a 1 (and probably a 2) on the Kardashev Scale, and have the gumption and unity to coordinate a vast engineering project with sweeping social ramifications.

Some of the larger stellar megastructures are so big that most entire solar systems won't have the resources to make them. This means one of several things:

  • The creators have a cheap FTL stardrive and can whisk in materials from far away.
    • If you've got cheap FTL, though, why spend so much time and energy building such a place? You could search the cosmos for promising worlds instead. The GM might need to ponder this one and have an answer.
  • The creators are very long lived and/or determined enough to spend generations hauling resources from distant systems. Even assuming the multi-generational path, imagine the power needed to move the bulk of one system several light years to another.
  • Alternately, it could be that Dark Matter occurs not at the edges of the universe, but relatively close to normal matter. Perhaps dark objects, or even dark systems, exist just outside normal systems. Since Dark Matter does not interact with electromagnetism (or visible light), this could make the universe a more cluttered and hazardous place than is normally envisioned. Some stellar megastructures might then be invisible to the naked eye, or feature structural parts that are invisible. Such a culture would need a way to detect structural damage, so they'd either have technology for "seeing" dark matter, or they'd have evolved naturally to "see" it. Awareness of nearby dark matter may be what inspired them to build huge structures, or the huge dark structures might be what hides these structures from detection by modern human science.
  • The creators can make reliable energy/mass conversions on a super-industrial scale.

If they've mined nearby systems, there may be a number of rogue stars or rogue planets in the interstellar neighborhood of the megastructure, or the absence of such from nearby systems may be the noteworthy clue that a megastructure is near.

All such megastructures will need some form of gravity. Many will just be massive enough to produce their own. Thinner or less massive megastructures may rotate to simulate or create gravity. There's also the option of Phlebotinum providing the gravity.

They will need life support systems, as well. Some will have complete transplanted ecosystems aboard, and no longer rely on that now-redundant life support machinery. However, during the creation status they almost certainly needed such systems, and they'd be useful to keep dormant but well maintained in case of an emergency such as a partial depressurization. For more on the dangers of deep space without life support, see Space Exposure.

However, the aliens might have somehow evolved in outer space, or used genetic engineering to insulate themselves from vacuum and temperature variations. If they are accustomed to floating in hard vacuum, it may be very difficult for humans to interact with them or live on their megastructures.

Exploring the larger megastructures could form the spine of an entire campaign, and take life-times in-character. Why would such a structure need exploring, you ask?

  • The designers may have been precursors, and are now a lost civilization. The megastructure is empty, or has "reverted" to wilderness.
    • They exited our galaxy, but left a few toys behind.
    • They transcended physical form and moved into remote regions of the fourth dimension.
    • In the case of a Tipler Cylinder or other megastructural time machine, they may have vanished into another era.
    • A partial life-support failure (or other disaster) killed off most of the inhabitants of the megastructure, and isolated the survivors. They still exist, but have lost much of their former glory and technology.
    • They are made of dark matter, are invisible or out of phase, and are watching even now.
  • The enemy might be hostile, or have a hostile faction.
    • War between extremely advanced cultures is likely to involve weapons of mass destruction and star killers, but a campaign could be structured around a series of commando raids, or a cold war and espionage between two intergalactic cultures.
    • Earth may have been enslaved, mined, or swallowed up by an aggressive megastructure culture. The PCs are now runaway slaves or secret freedom fighters. keep a low profile though, because the masters have serious power to turn against you if provoked.

See Also:

For further ideas, see Megastructure and the individual pages of various megastructure concepts.
Many, but not all, Stellar Megastructures are also Stellar Engines.
Stellar Engineering is the form of engineering concerned with creating or modifying stars.
Star Lifting is a proposed form of mining that could be used to remove large portions of a star for various purposes.

Alien megastructure? Tabby's Star continues to baffle scientists
Astronomers have discovered another mysterious dimming star

The list of stellar megastructures is at the megastructure page, and also included in a larger list on the Interstellar Terrain page.

Game and Story Use

  • The text above should suggest plenty of ideas.
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