Everyone knows the Deathstar. By now, it’s surely an iconic depiction of power and technological potential. As such, it’s a pretty good example of the bizarre field of astroengineering. In other words, designing and engineering objects on an astrophysical scale. Astroengineering is currently of purely academic interest to us humans. Our technology isn’t yet capable of even beginning to construct such vast masterpieces of technology. As such it’s relegated to fields like “exploratory engineering” and science fiction.
The fact remains though, that an advanced civillisation might be able to create such an object (although hopefully not with the intention of destroying planets). Scientists working at SETI have already discussed the possibility of looking for such giant machines. Indeed, the discovery of an artificial planet or moon around another star could give unequivocal evidence of an extraterrestrial civillisation. This was the reason behind my reading about all of this. With the planned space telescope missions aiming to image terrestrial sized planets around other stars, is there a possibility we could actually image an artificial object? What implications might that have for humanity’s further exploration of the Galaxy? Should we try and contact them? Might they already know about us? It opens up a whole saga of interesting thought experiments… The biggest question then is, if we want to find intelligent life with all of these powerful new telescopes – Should we be looking for the Deathstar?
Astroengineered artefacts are a recurring theme in many science fiction plotlines. Larry Niven’s “Ringworld” is all about an artificial ring shaped object in orbit around a star. Engineered to make the entire inward facing edge a habitable area, the ringworld is an artificial “planet” with many thousand times the surface area of a real planet like Earth. The Halo series of games features a similar ringworld concept (the “Halo” itself). These differ from “space stations” in that they’re much much bigger! As an example, a typical sci-fi space station (Babylon 5, for instance) would be seen as little more than a couple of pixels on the scale shown below, to the right.
The Deathstar, as it happens, is maybe not the best example I could’ve chosen. While such an object would be a massive feat of construction generating stresses and strains which no known engineering materials could stand up to, it’s still relatively small even compared to the Earth. The first Deathstar (the one destroyed in Episode IV) is actually a lot smaller than Ceres, currently the smallest recognised dwarf planet. Given the difficulty in imaging objects in orbit around other stars (and the greater difficulty in even finding interstellar objects), even a space station this size might slip under the proverbial radar. Objects this size are difficult to detect, even in the fringes of our own solar system. Not that I’m saying there’s a Deathstar lurking in the Kuiper belt. You never know though…
There are, however, much larger astroengineered objects which might be easily recognisable as such. For instance, the famous theoretical physicist Freeman Dyson proposed a concept which science fiction authors have adored ever since. The so-called “Dyson Sphere” is a theoretical way to harvest all (or almost all) of the light from a star. Science fiction stories (including at least one Star Trek episode) tend to depict a solid shell around a star, harvesting all the star’s light. In reality, this is the least plausible model, largely because a single solar system probably wouldn’t contain enough material to build such an object. What’s more, with no means of fixing it in place, the shell would be free to drift with respect to the star, possibly with disastrous consequences.
A more likely scenario is known as the Dyson Swarm – a vast array of smaller satellites in orbit around the star. Layer upon layer of these satellites could be used to capture increasingly lower wavelengths of starlight, harvesting a ridiculous amount of energy. A further concept has been devised, known as a Matrioshka Brain, where all of this energy is used to power mind bogglingly large calculations. With that kind of computing power, a civillisation could conceivably model an entire universe inside their own version of the internet. But this is degenerating into wild and flagrant speculation.
Nonetheless, Dyson Swarms are hypothesised to be detectable by an excess of infrared, and only a small amount of the star’s actual light escaping. Thus far, nothing matching that description has been discovered. Though many star systems, including Sirius, show an infrared excess, these can all be attributed to dust.
Who knows… When ESA launches Darwin, perhaps we might discover something unexpected!