I’m working on star system generation for my game Fleet Commander and trying to follow some principles of star system mechanics, e.g. distribution of star classes.
I am a complete ignoramus about astronomy (is that even the right term for this?) and figuring it out as I go so anyone who knows their stuff I’d welcome any pointers.
Anyway in the game there are a race of aliens who are building a Dyson sphere and it occurred to me that, when complete, it would trap all the light being emitted from the sun making the system very hard to see. Wouldn’t it? Would you, how would you, know there was a star system there?
The Dyson Sphere could absorb the star’s energy and re-radiate it as infrared radiation. Presumably getting rid of waste heat would matter in the long term. So you could imagine sensors would see an unusually strong infrared signature from that star system, suggesting the presence of some sort of large structure.
Similarly, if the Dyson Sphere has a significant mass (and it would), it could slightly bend the light of background stars as they pass by.
You might even consider localized hot spots on the surface of the sphere. They might emit light differently. Perhaps this is due to lack of uniformity in construction or perhaps hits from objects in the solar system, like passing meteors that, over time, have caused imperfections.
Also, keep in mind the Dyson Sphere would not likely enclose the whole solar system, but rather just the star. So there would be orbiting planets as well that would indicate a stellar system. Ah, but would we detect those things? After all, searching for exoplanets now can be tricky and often we use the wobble of the parent star to do so.
During construction, the transit method would still work to observe the system from a distance. Also, if the Dyson Sphere exerts a gravitational influence on the nearby planets, we might observe unexpected orbital patterns. (Think of a Dyson Sphere in our solar system, for example, and how that might not matter to Earth – at least orbitally speaking – but could show perturbations with Mercury.)
The Time Ships by Stephen Baxter and Pandora’s Star by Peter Hamilton do cover the idea of a Dyson Sphere. Hamilton’s in particular involves an interesting scenario that I won’t spoil here.
I’m imagining that if you have the capability to actually construct such a structure you can probably convert most of the captured heat into some more useful form of energy and route it elsewhere. If not, I guess there is a risk the sphere overheats. Perhaps re-radiating some of the captured heat would be a safety precaution.
I’m imagining my aliens living in structures constructed on the outside surface. If they are machines the lack of light and heat wouldn’t bother them.
A Dyson sphere system would be easy to detect, since the outer surface of the sphere’s panels would certainly radiate at least 14% of the star’s energy output, and that would show a much higher temperature than the cosmic background. Any infrared imaging would show it as a low-intensity radiative source. Depending on the capabilities of the detecting civilization, it might be taken at first sight for a brown dwarf, but it would show a completely different emission spectrum, so it can’t be.
In fact this is how we expect to detect Dyson spheres, should they exist: a body that shows a black-body spectrum but has a temperature one or two orders of magnitude higher than the empty space around it. This is a far better tell-tale sign than any gravimetric indicators.
If some alien civilization capable of constructing a Dyson Sphere were to harness the energy of its star, it would presumably need to address the immense heat generated by such a structure. While some of the captured energy could likely be converted into useful forms, due to the Second Law of Thermodynamics, not all the energy could be efficiently converted. Some portion would inevitably become waste heat, which would have to be managed somehow to avoid overheating the Dyson Sphere. (You can actually calculate how long heat build up might take for a given volume.)
Now, granted, the aliens here can be imagined to have other technologies at their disposal. Perhaps they can generate artificial black holes and so on.
So part of this might more speak to the motivation for building such a structure in the first place. That’s often where I’ve found the most interesting science fiction lay: considering the psychology of a race that would build such a structure.
In terms of where the aliens live, living on the inner surface would allow the inhabitants to have direct access to the star’s light and energy. The outer surface, less so. Which then goes back to the psychology of the race and why they created the structure.
Okay that’s good. For game purposes I need an observable system. Otherwise I’d have to find some other way to alert the player to its presence. Then again I don’t want it to be too obviously interesting so that the player makes a beeline for it. Will have to think about this.
Keep in mind, too, observable from where? Light takes time to reach something. So if your hard-to-find system is, say, sixty light years from wherever, then it would take any radiation that many years to get there.
You then have to consider radiation swamping. Space is filled with all sorts of radiation (cosmic microwave background, other stars, and distant galaxies), so the signal from a Dyson Sphere could easily be lost in the noise, unless someone was specifically checking that region. (Hamilton’s book gives a particular scenario for why the Dyson Sphere was observed, albeit indirectly.)
Now, if this is a case where the player is in a spaceship traveling around and they get near the system, they might see an Oort cloud, similar to ours. That would certainly indicate something. As would the presence of other planets. Detecting those things would be harder than detecting the actual emissions from a distance but, again, it depends on if the player can be traveling around. Or if there are probes that have also been traveling around and the player gets reports from them.
Hrmm… this is interesting detail and I am having to weigh how much that helps. I kind of want enough detail to make exploration interesting and with some “real feel” without bogging down the actual gameplay with “reality”.
How about something like this? The gravitational effects of a Dyson system could potentially have an impact on nearby stars. Generally, the distances involved are so vast that any detectable influence would likely be very subtle. But this is future tech, right?
For example, Alpha Centauri, which is about 4.37 light years away from our Sun, is close enough that the gravitational pull from a massive object like a Dyson Sphere around our Sun could slightly perturb its orbit. But, again, this effect would be extremely small, especially considering the sheer mass and volume involved.
So broad idea: if the Dyson system were large and particularly massive, it could cause minute changes in the motion of nearby stars. Over time, this could lead to a slight drift in their position, which might be detectable with advanced astronomical tools that track the position of stars with precision. So let’s say the systems in your future have all that historical data and start to ping about the possible discrepancies.
That leads someone to check more closely the emission signature from that region of space and, sure enough, there is a higher infrared emission than expected if the space was just empty. Hence, a mission is sent out to investigate …
Also, the reason time is relevant here is that let’s say the aliens built the Dyson Sphere over the course of three hundred years, ending a century ago (from our perspective). But the construction was presumably not instantaneous. Which means over the course of that 300 years, light from the star would have been increasingly dimming.
Which, again, maybe was picked up by remote observation systems but wasn’t really flagged as important. Or was flagged but everyone ignored it.
I like the general thrust of the idea: once you start exploring the systems in the outer rim of the sector, anomalies are detected that eventually lead to the Dyson-sphere system being identified and it can then be explored.
So it starts hidden and unavailable. But at the right point becomes available. This solves my game design issue.
A conceivable idea is that a Type II Kardashev civilization that doesn’t want to be too easily detectable might be able to fake an emission spectrum for a star by installing certain emitter machinery on the outer layer of the Dyson sphere. I have no idea how that could be done, but if they can build the sphere in the first place, then doing this shouldn’t be out of their ability. With this premise, resorting to mass calculations and gravitational anomalies may be the best next way to detect them, but it would take a lot more time and effort to do so.
That’s also a neat idea. They fake the output of an uninteresting star to hide themselves. They’d surely have the available power needed for such an exercise.
Indeed! That’s why I say the psychology actually matters quite a bit here. What are they building this thing for? It could sound obvious and “practical” – but then was there no other practical way to get energy? Was this race not exploring the rest of their solar system or space? Had they and decided they just didn’t like it?
Thus, are they hiding? Or not so much hiding as putting up a “Do Not Disturb” sign. And if they are hiding, from what? Just from observation? What compels a race to build a megastructure like this?
Perhaps it’s not so much hiding as it is that if this civilization has advanced to the point where it’s able to manipulate the entire energy output of a star, they might be looking to support a massive population, or sustain colossal computational networks, or power sophisticated technologies. It might be driven by the need to power other megastructures. Or maybe artificial environments or interstellar colonization efforts.
Why something is built, particularly on such large scale, is one of the more fascinating areas to consider. If the race fears something, that’s interesting! What could they fear so much that they had to enclose their star? If they are powering other projects, that’s interesting! What could those possibly be that require so much raw power?
That could be the whole premise of a game, in fact. Or at least a subplot. If we have reason to think that someone doesn’t want to be found, immediately one would be curious about it…
In my game I want this to be ambiguous. Partly because I am not an inscrutable, cosmically overpowered, alien. Partly because what I come up with is unlikely to be as satisfying as what the player guesses or imagines. But I imagine there are uses for stellar conversion energy quantities.
Yeah, personally, I like keeping aliens alien. And that can include their motivations. The key, however, are the hooks for the reader/player. People will assume there is a reason why things are done, since that’s the basis of a lived universe. Whether we are able to figure them out or not is another issue.
I think that’s the tricky part in sci-fi. People like resolution to ideas and if there isn’t any resolution, they can feel cheated. On the other hand, if it’s established that the aliens are inscrutable, that can work. (Peter Watts is an author that does this quite well in Blindsight and Echopraxia.) Consider the first Rendezvous with Rama book. Really nothing much is answered there at all. And I would argue the later books suffered as they tried to answer more and more.
Short version: I agree with the ambiguity. I think it’s more about suggesting the wide possibilities or at least teasing about them, which can prompt and fuel player imagination.
Gravity, magnetic field, infrared (heat), occlusion of background stars (from a moving point of view, or if the star is part of a binary system). Perhaps some other form of electromagnetic radiation from the civilization on the sphere itself.
Hang on. Surely that depends on where the mass for the Dyson sphere came from? If we were to (eg.) disassemble Jupiter and the Oort Cloud for the materials to build the sphere, and installed all of that mass inna homogeneous shell around the sun, then the total gravitational influence on α Centauri would be the same, and would have the same barycentre. All that would change is the emitted radiation.
If we nicked the mass from α Centauri in the first place, that would be different.