For a project looking for the signature of an advanced extraterrestrial civilization, the name Hephaistos is an unusually apt choice. And indeed the leaders of Project Hephaistos, based at Uppsala University in Sweden, are quick to point out that the Greek god (known as Vulcan in Roman times) was a sort of preternatural blacksmith, thrown off Mt. Olympus for variously recounted transgressions and lame from the fall, a weapons maker and craftsman known for his artifice. Consider him the gods’ technologist.
Who better to choose for a project that pushes SETI not just throughout the Milky Way but to myriads of galaxies beyond? Going deep and far is a sensible move considering that we have absolutely no information about how common life is beyond our own Earth, if it exists at all. If the number of extraterrestrial civilizations in any given galaxy is scant, then a survey looking for evidence of Hephaistos-style engineering writ large will comb through existing observational data from our own galaxy but also consider what lies beyond. Which is why Project Hephaistos’s first paper (2015) searched for what the authors called ‘Dysonian astroengineering’ in over 1000 spiral galaxies.
More recent papers have stayed within the Milky Way to incorporate data from Gaia, the 2 Micron All Sky Survey (2MASS) and the accumulated offerings of the Wide-field Infrared Survey Explorer, which now operates as NEOWISE, analyzing the observational signatures of Dyson spheres in the process of construction and calling out upper limits on such spheres-in-the-making in the Milky Way. Such objects could present anomalously low optical brightness levels yet high mid-infrared flux. This is the basic method for searching for Dyson spheres, identifying the signature of waste heat while screening out young stellar objects and other factors that can mimic such parameters.
This article is occasioned by the release of a new paper, one that homes in on Dyson sphere candidates now identified. And it prompts reflection on the nature of the enterprise. Key to the concept is the idea that any flourishing (and highly advanced) extraterrestrial civilization will need to find sources of energy to meet its growing needs. An obvious source is a star, which can be harvested by a sphere of power-harvesting satellites. The notion, which Dyson presented in a paper in Science in 1960, explains how a search could be conducted in its title: “Search for Artificial Stellar Sources of Infrared Radiation.” In other words, comb the skies for infrared anomalies.
I strongly favor this ‘Dysonian’ approach to SETI, which makes no assumptions at all about any decision to communicate. As we have no possible idea of the values that would drive an alien culture to attempt to talk to us – or for that matter to any other civilizations – why not add to the search space the things that we can detect in other ways. However it is constructed, a Dyson sphere should produce waste heat as it obscures the light from the central star. Infrared searches could detect a star that is strangely dim but radiant at infrared wavelengths, and we might also find changes in brightness as such a ‘megastructure’ evolves that vary on relatively short timeframes.
Funding plays into our science in inescapable ways, so the fact that Dysonian SETI can be conducted using existing data is welcome. It’s also helpful that in-depth studies of particular Dyson sphere candidates may prove useful for nailing down astrophysical properties that interest the entire community, especially since there is the possibility of ‘feedback’ mechanisms on the star from any surrounding sphere of technology. We go looking for extraterrestrial megastructures but even if we don’t find them, we produce good science on unusual stellar properties and refine our observational technique. Not a bad way forward even as the traditional SETI effort in radio and optics continues.
The number of searches for individual Dyson spheres is surprisingly large, and to my knowledge extends back at least as far as 1985, when Russian radio astronomer Vyacheslav Ivanovich Slysh searched using data from the Infrared Astronomical Satellite (IRAS) mission, as did (at a later date) M. Y. Timofeev, collaborating with Nikolai Kardashev. Richard Carrigan, a scientist emeritus at the Fermi National Accelerator Laboratory, looked for Dyson signatures out to 300 parsecs.
But we can go earlier still. Carl Sagan was pondering “The Infrared Detectability of Dyson Civilizations” (a paper in The Astrophysical Journal) back in the 1960s. In more recent times, the Glimpsing Heat from Alien Technologies effort at Pennsylvania State University (G-HAT) has been particularly prominent. What becomes staggering is the realization that the target list has grown so vast as our technologies have improved. Note this, from a Project Hephaistos paper in 2022 (citation below):
Most search efforts have aimed for individual complete Dyson spheres, employing far-infrared photometry (e.g., Slysh 1985; Jugaku & Nishimura 1991; Timofeev et al. 2000; Carrigan 2009) from the Infrared Astronomical Satellite (IRAS: Neugebauer et al. 1984), while a few considered partial Dyson spheres (e.g., Jugaku & Nishimura 2004). IRAS scanned the sky in the far infrared, providing data of ≈ 2.5 × 105 point sources. However, nowadays, we rely on photometric surveys covering optical, near-infrared, and mid-infrared wavelengths that reach object counts of up to ∼109 targets and allow for larger search programs.
The Project Hepaistos work in the 2022 paper homed in on producing upper limits for partial Dyson spheres in the Milky Way by searching Gaia DR2 data and WISE results that showed infrared excess, looking at more than 108 stars. We still have no Dyson sphere confirmations, but the new Hephaistos paper adds 2MASS data and moves to Gaia data release 3, which aids in the rejection of false positives. Gaia also adds to the mix its unique capabilities at parallax, which the authors describe thus:
…Gaia also provides parallax-based distances, which allow the spectral energy distributions of the targets to be converted to an absolute luminosity scale. The parallax data also make it possible to reject other pointlike sources of strong mid-infrared radiation such as quasars, but do not rule out stars with a quasar in the background.
Notable in the new 2024 paper is its description of the data pipeline focusing on separating Dyson sphere candidates from natural sources including circumstellar dust. The authors make the case that it is all but impossible to prove the existence of a Dyson sphere based solely on photometric data, so what is essentially happening is a search for sources showing excess infrared that are consistent with the Dyson sphere hypothesis. The data pipeline runs from data collection through a grid search methodology, image classification for filtering out young stars obscured by dust or associated with dusty nebulae, inspection of the signal to noise ratio, further analysis of the infrared excess and visual inspection from all the sources to reject possible contamination.
This gets tricky indeed. Have a look at some of the ‘confounders,’ as the authors call them. The figure shows three categories of confounders: blends, irregular structures and nebular features. In blends, the target is contaminated by external sources within the WISE coverage. The nebular category is a hazy and disordered false positive without a discernible source of infrared at the target’s location. Irregulars are sources without indication of nebulosity whose exact nature cannot be determined. All of these sources would be considered unreliable at the conclusion of the pipeline:
Image: This is Figure 5 from the paper. Caption: Examples of typical confounders in our search. The top row features a source from the blends category, the middle row a source embedded in a nebular region, and the bottom row a case from the irregular category. On these scales, the irregular and nebular cases cannot be distinguished, but the nebular nature can be established by inspecting the images at larger scales. Credit: Suazo et al.
In the next post, I want to take a look at the results, which involve seven interesting candidates, all of them around a type of star I wouldn’t normally think of in Dyson sphere terms. The papers are Suazo et al., “Project Hephaistos – I. Upper limits on partial Dyson spheres in the Milky Way,”
If the civilization needs to keep growing, then once the swarm/sphere has been completed, how does the economy continue to grow? Without another source of energy, perhaps from other stars, the economic growth effectively halts. The civilization then becomes rather static, changing form but restricted to a certain size.
Our terrestrial economic system would fail without continuous growth that requires increased energy use.
If these swarms exist and are active with extant civilizations, then the fears of those concerning METI (“Dark Forest” believers) are wrong, as these systems are beacons indicating their presence. One can only hope that the civilizations are extant, indicating that no predator has destroyed them, rather than ruins after depredation.
I would hope that the energy argument is a side effect, rather than a driver. I would prefer that the swarm is evidence that a civilization has expanded its living space into habitats as a maximal use of planetary resources to create diversity. It is the radiating habitats that are the source of the IR signals. In this scenario, expansion continues as habitats start to migrate to other stars. If so, one would expect the stars with IR signals to be clustered in space as the civilization expands.
It is also possible that these Dyson objects are just the detritus of a civilization’s transition state from a material to an immaterial one through some sort of transcendence.
While the search is worthwhile, I am skeptical that such mega-engineering structures exist, and we will discover that the data is yet another in a lineage of false positives of ETI. Hopefully, imaging of the candidate stars will determine whether these structures exist or not. A Dyson swarm should be distinguishable from a natural dust or asteroid disk by its orbital coverage of its star.
I agree Alex. One would think that a civilization that can build a ‘Dyson Swarm’ for energy and natural resources needs would have a very advanced technology. Why then does that civilization not deploy an instrumentality more sly? Solving its energy needs it very subtle ways. Something too ‘brutish’ about this idea , to me, feels rooted in Earth’s human history. I think, if , humankind survives to an advanced state its core technological state is unpredictable.
My impression is that Dyson put this idea forward to stimulated discussion of possible ideas about the observability of advanced civilizations. Fine to explore this concept but other more crafty designs may be in order.
I’m with you guys on this. A Dyson sphere is anything but subtle!
So help me, I still half-think Miranda was strip-mined
While we cannot yet answer such an idea definitively one way or another – one probe flyby almost four decades ago is hardly sufficient – it would not completely surprise me.
We likely have many celestial objects staring us in the face that are artificially manipulated which our just awakening minds are far from being able to discern yet. We could be living in a Kardashev Type 3 galaxy and be as clueless as a colony of ants in a construction site.
https://en.wikipedia.org/wiki/Miranda_(moon)
We have also just barely begun to explore the planetoid and comet belts of our Sol system. Don’t be surprised if we find a few of them having been mined as well for reasons that include refueling, repair, and self-replication:
https://www.youtube.com/watch?v=zQTfuI-9jIo&t=2s
This article considers self-replicating probes using current technology:
https://arxiv.org/pdf/2005.12303
Dyson swarms can serve various functions besides energy collection, they just as well could be a vanity project, or collection of both natural or engineered biospheres.
There are actually several candidates for mega structures identified in the studies. Unfortunately we lack means to confirm them.
Part of the problem some people are having with Dyson Shells/Swarms stems from their original concept as a collection of habitats for organic beings. But what if they were artificial beings themselves, utilizing part or all of a solar system for resources?
If nothing else, I know when Robert Bradbury discussed this concept just over twenty years ago now, it certainly changed my paradigm on the subject – and the possible reasons for them to exist.
You may find his thoughts on the subject here:
https://web.archive.org/web/20090223093348/http://aeiveos.com:8080/~bradbury/MatrioshkaBrains/index.html
Here is an article summarizing Bradbury’s ideas:
https://bigthink.com/hard-science/are-we-living-inside-a-matrioshka-brain-how-advanced-civilizations-could-reshape-reality/
I have often wondered if our place in the Milky Way galaxy is akin to an ant colony at a human construction site: We do not really comprehend what is really going on, or even believe what we could be seeing. Then we need to hope that the builders do not dismiss us as your average construction worker would an ant colony.
Orion’s Arm is another good place to expand thoughts on the subject:
https://www.orionsarm.com/eg-article/4845fbe091a18
Artificial beings make a lot of sense. However, they cannot ignore physics. Either they operate to keep expanding, or they become static. In that regard, they are up against the same constraints as our organic civilization.
I am dubious about the concept of Matrioshka Brains. If they are to continue, they must also keep acquiring more energy and material if only for new data storage. This implies that must still be able to interact with the real universe and not be just a construct for a massive virtual world[s]. Once they have used up all their systems resources, and maxxed out the energy harvesting, then what? Their only option is either stagnation or acquiring new resources by physically exploiting another system.
Maybe an MB virtual world of thinking agents existing for the lifetime on the stars main sequence is enough, but I have to think that expansion is still desirable. As I have noted in the past, expansion at even a slow rate means that we reach KII status in only millennia. While the galaxy offers another expansion phase to KIII, the limitations of c imply that growth rates slow to a trickle. If the growth rate remains at the rate of KI->KII (with c limits violated) then the galaxy reaches its limit in millennia too. If so, it would be full of MBs or Dyson megastructures by now. Every model of expansion by star hopping shows that the galaxy would be fully exploited within the time we have emerged as genus Homo.
While that doesn’t mean that there cannot be other civilizations, perhaps housed in Dyson megastructures or as MBs, it does imply that they are not “grabby” and accepting of their resource limitations. Perhaps they then decline leaving their structures as dead or inactive monuments. Or they have coincidently relatively recently emerged and we will meet them at some time in the future as our expansions eventually intersect.
There is no reason for a civilization to constantly aggressively expand.
It’s an old argument used by proponents of empty universe theory who argue whole galaxy should be colonized by now.
Much as information theory can be used to estimate the computational capacity of a black hole, I imagine it could be used to estimate the same for a Dyson swarm/sphere. I’ve not seen that done yet (near as I can tell).
I forgot to add two more reasons to make a Dyson style structure: As a method for pushing lots of light sail vessels to explore other star systems and as a formidable weapon:
https://www.orionsarm.com/eg-article/48fe49fe47202
I don’t want the latter to be an actuality, but if intelligent life follows the patterns here on Earth, then they may expend the resources and funds on weaponry before or over anything else.
This may also answer why those who can and do build Dyson Shell/Swarms do so without fear of the dark forest concept because only another species with equal sophistication could match them.
I don’t think we should count on Dyson spheres being detectable by heat. https://phys.org/news/2024-04-ghost-particle-scales-precise-neutrino.html – the mass of electron neutrinos has been found to be less than 0.12 eV/c^2 by cosmology, and 0.8 eV/c^2 by direct measurement. Correct me if I’m wrong, but given the Boltzmann constant is 8.6e-5 eV/K, this suggests a star with a 6000 K photosphere could throw away 0.8 eV/c^2 of thermal energy for each neutrino generated at that temperature. So for every joule of free energy spent making neutrinos, you can cool the Dyson sphere by at least 1 joule, maybe 8 joules, maybe more depending on how the neutrino masses finally come out – comparable to heat pump efficiencies. Of course, first you have to figure out how to make neutrino/antineutrino pairs out of pure energy, but the Dyson sphere builders might have managed it. Neutron stars rapidly cool spontaneously by this same mechanism. There are some conveniences: starting with a yellow subgiant star like Eta Bootis, you need merely pave the surface with heat engines and neutrino refrigerators, with some very good radiation and EM shielding, and then you’d have roughly 80,000 Earths’ worth of living space at roughly Earth gravity.
I agree that highly advanced civilizations may invent ways to get around thermodynamics, or our interpretations of it. So these search techniques may have false negatives. But not all civilizations capable of building things these techniques can find may be hiding. The search is highly worthwhile.
And if we somehow detected the remains of, e.g. a Dyson sphere that would be highly valuable information.
You’re right, of course – I don’t mean to ignore the actual candidates. That part of the article here hasn’t posted yet, but looking at the last preprint, Dyson spheres/swarms are understandably similar in appearance to optically thin debris disks. I don’t really understand why they say “M-dwarf debris disks are very rare objects” when they would seem to have found several; it must have something to do with how they confirm them? It should be interesting to think about how to distinguish an uninhabited, “dead” Dyson swarm of rocks from an inhabited “live” swarm of space habitats.
It should be up in just a few hours, Mike.
@Mike
This is the first idea that came to mind when reading the article: it is a question of a detection of infrared radiation correlated with the decrease in brightness of the star in the spheres of Dyson. But if an ETI civilization is capable of creating such a structure, it would be very surprising if it did not consider to “mask” also this infrared radiation, for example through a system of energy in circuitclosed or by controlling the atomic structure of these radiations.
Same for the brightness of his star: knowing that his sphere of Dyson will oculter – so signal it to others! – do you think that our ETI did not intend to deceive us by creating an artificial magnitude of its star? If she is able to create a Dyson sphere, she is surely able to create a giant mirror reflecting light or perhaps using a gravitational lens, to remain discreet ?
Building a Dyson sphere involves two things:
either the structure has for purpose only its planet (shield?) which supposes then that our ETI has no look towards the space and/ or totally mocks the visibility of its sphere, it would be unlikely even absurd. We can also think that she is quietly building her “Mechanic”, without worrying about the space [of us] because she has the assurance of disappearing or countering any other civilization that would try to approach her: mastery of energy (type II or III) ; modification of the space-time frame; change of state etc. In other words, if we detect a Dyson sphere it is because it will let us see! (I put aside the interesting assumption that a sphere would be a living organism so as not to complicate the debate.)
Second hypothesis: the ETI would be subject to a serious problem on its planet that would require the construction of this sphere for its preservation. This does not make much sense because it would have to spend a large amount of energy on this construction while it would be threatened and perhaps in the extinction phase. According to the universal principle of least means and maximum efficiency, the ETI would then probably have chosen a better solution such as terraforming; colonization of a neighboring planet or sending Neuemann probes etc. (I think we must stop the madness with these stories of “intergalactic black forest” which are only a reflection of our anxieties and the modern version of the big bad wolf or deu syndrome David Vincent:)
The research has are interesting, but in what seems to me important, it is not all these speculations, but the INFORMATION that would constitute the existence of these spheres. What would this information bring us? what would we deduce? what would we do with it?
Finally, I would like to emphasize the following point: we have assembled the ISS around the earth. Is it not the embryo of a future Dyson sphere at least of a material technological structure set up by living beings? I propose here the idea of reflecting on the fact that the function of such a material structure can evolve over time. It will surely be according to the evolution of the capacities of its creators, the maistrise of their energy resources etc. What poses the following problem: assuming that we discover this object, will it be the same when we reach it?
I am not an expert on these structures and these are only suggestions ;)
Fred
Energy is indeed important within our time-space coordinates.
It is also possible that these Dyson objects are just the detritus of a civilization’s transition state from a material to an immaterial one through some sort of transcendence.
How far must a virtual machine extend before it is deemed Reality? Taken as a whole, the entire universe can be approached as a realistic model. Many family pet dogs watch television. With even more constrained minds when compared to the task, humans watch ever so tiny portions of the model we call the Universe.
I don’t really expect any of these infrared anomalies will ever be found to be an artifact of an extremely powerful civilization, one operating on a scale involving entire planets, stars and planetary systems. Even if one can conceive of a civilization lasting long enough to develop such near-godlike powers, its difficult to come up with a reason why they would want to.
Our desire to speculate about such colossal powers is that we simply haven’t been able to explain away the embarrassing fact that much easier means of interstellar communication have so far failed to turn up. Instead, we fantasize about brooding, almost supernatural intelligences hammering away at the forges of heaven creating…what? SETI enthusiasts are fascinated by technology, seduced by our own pathetic dabbling in those arts, and think of this sort of aggressive hyper-industrialism MUST be the sign of true intelligence, genuine civilization.
I suppose its not impossible, the universe is old enough and big enough to make almost anything possible, somewhere, sometime. But I suspect a truly wise and advanced culture would find less spectacular and disruptive hobbies, such as securing eternal life, security from cosmic catastrophe, true scientific understanding, or even searching for other species. Making bonfires of planets and harnessing the power of entire suns seems like an awful lot of sturm und drang. It makes sense to us mostly because we’re desperate for some sort justification of our own fantasies. We like to think of ourselves as an aggressive tribe of explorers, enterpreneurs and conquerors, and we can’t imagine anyone worthwhile not being the same. We listened for microwave signals and we didn’t find any (after listening for a whole half century!) So now we fantasize about Marioshka Brains, Dyson megastructures and Kardashev Kultures. Surely, they must have left some imprint on the cosmos.
I suspect intelligent civilizations are out there, but they are few and far between for the reasons I have spelled out previously. They are highly separated in space and time, and there is little incentive for any of them to expand indefinitely until they are capable of leaving a footprint that can be detected at galactic distances. Once they have reached a certain level of comfort and security they simply will have no need to continue expanding. and “progressing”. The few crazy enough to follow that psychotic path will eventually kill themselves off or stew in their own poisons.
Still, I welcome this interest in sifting through old astronomical catalogs and databases. Something of interest is bound to turn up, even if it isn’t evidence of technological overreach, but just some interesting little astrophysical process we haven’t stumbled onto yet.
No amount of seeking will yield what is sought when the sought is really the Seeker, but is not so recognized. Until the delusive acknowledgement of an “I”, there is neither “I” nor “not-I”, neither Self nor other, only Presence which includes both Existence and Consciousness.
That acknowledgement of an “I” includes the acknowledgement of the “not-I” with the body-mind complex and everything else, even the constraints of space and time, matter and energy, with a beginning and an ending for all, including all that is yet to be discovered.
And even immortality is a quixotic quest within the bounds of time and space; recognition of the delusive nature of the “I” includes an end to the delusion of the “not-I” and of all constraints, explicit or implicit.
In the meantime there are plenty of theories and trinkets to command one’s attention.
Plenty of possible candidate artificial signals were discovered, however none were repeated and if they were artificial they would be most likely “leakage” from technological activity.
There can be quite a few civilizations out there, but none that are interested in contacting ours for numerous reasons.
Any civilization capable of such an engineering feat must certainly be orders of magnitude more efficient than us. I would therefore not expect to see their thermal signature to be strictly blackbody… rather I’d expect unused energy to be, for example, converted to maser emissions beaming the ‘leftovers’ to platforms farther out in their system. We should only expect to see the ‘scraps’ of the ‘leftovers’.